I love that someone as knowledgeable as you is still learning new things and open enough to talk about it. another great video... appreciate being able to learn with you!
Thanks, Joe. I'm a strong believer in the old "use it or lose it" philosophy when it comes to learning.....and you should never stop sharing what you know with others.
What I appreciated most I think was the solution and the method of finding the source of it. As a teenager hobbyist I was implored to fix a red plate output stage on a rather powerful Bass amp. Shook my head and said I would if I knew what was going on there. Now I think I do, thanks for closing such circles for me.
You're welcome, Lee. I think as our lives progress and we gain more and more experience with all things, including electronics snafu's, there is a snowball effect.....gathering mass (knowledge) as we progress. I'm glad that our videos have aided your progress.
I recently read an article addressing point to point, turret board and pcb wiring schemes that explains the pros and cons. The overwhelming similarity was how important it was to pay attention to lead dress and or lay out due to the very thing you found here. I am glad I read that article prior to me building my amp to avoid frustrations. Thank you again for all these videos. Absolutely priceless information and your teaching approach is top notch for me.
I just keep finding more excellent video's on your channel. Car show; In high school, I found a half ton, 1948, 5 window or wraparound window Chevrolet with a perfect chrome front grill, outside windshield visor, the tranny was out, I believe it had a 235 or smaller straight 6 engine, but everything down to the faded green paint was original, nary a scratch on it just sitting there parked next to a shed. I aquired it for $125 and dad sold it to a collector for ? LoL I used to find classic vehicles like a bird dog bringing up pheasants when I was young. I always told him that we should sit on them for at least twenty years and then sell them at a greater profit and keep a few for ourselves, but he was always happy with an extra $500. He lived for the moment and that was it. Thanks again, Cheers!
Just another example of the adage “we are never too old to learn”. I kept thinking something was just odd about that waveform, but having never looked at an output of a reverb tank it didn’t dawn on me that the high frequencies in that 1K sine wave would be hypersonic or up to RF. That’s why I love working with electronics, just when you thought you had a good grasp on how a circuit was supposed to operate, a gremlin pops up. Back in my 800 MHz trunking two way radio tech days, I used to tell customers that “theoretically that radio can’t do what you have told me it did, but you anything is possible with electronics”. At the car show, you apparently have a friend that has taken OCD to an absolutely beautiful art form. The details on that 5 window pickup were perfection. Precise hose and cable routing and a perfect firewall, not full of holes or patched over holes, WOW.
A simple fix for a big problem. Another lesson, you couldnt tell there was a problem until something burn later. Unless you had it on the oscilloscope before calling it done! Again, beautiful build. Thanks for sharing.
First, very nice work with whoever called out the parasitic oscillation. It was a very remarkable interior. Second, on the car show segment, the El Camino showed us as much of your exterior as we will probably ever see in the reflection in the window glass. It didn't shatter, and your superhero identity and look is still hidden for the most part.
I agree, Joel. Viewer input is a valuable resource. I guess I'll have to wear a costume while making videos of shiny cars.....perhaps a fake beard and dreadlocks.
That was a great, great project to begin with, but the parasitic oscillation and how to find and eliminate it was a true cherry on top of it. Call me a nerd, but I really like it when some problem-solving is required, and a spiffy problem-solving you provided. Very well done, in all aspects of the project - congrats!
Hey I got the notification this time! I never got one for the last video. I only knew you had uploaded it because it showed up in the sidebar of suggested videos. Man I am so glad you are doing videos again! Some of my favorite content on TH-cam.
It does, and now the 6K6 sounds better has the 6V6 or whatever it was. It would be interesting to know how much loss there is through the reverb unit, i.e how much gain needs to be made up before and after.
"Not to my taste, but impressive workmanship". I'm heavy into your informative videos of late, sir, and this statement is a great example of the wisdom you dispense. Seems mandatory to have such an open-minded, but grounded, outlook where serious voltages are concerned. Thank you.
Awesome job, with all your knowledge and years of experience there was still something for you to learn and what is even more impressive is that you owned it and did not make any excuses. It takes a very secure person to do something like that, the world needs more people like you. To top everything off you were kind of enough to share this learning experience with us, my hats off to you sir. Again thank you for your channel and sharing your knowledge with us.
You're quite welcome, Michael, and I sincerely appreciate your analysis of the situation. Learning opportunities are far more important that petty pride.....and If I've never seen a phenomenon before, then it's quite likely that the majority of viewers have never seen it either. This channel isn't something I do for you all. It's something we do together.
It's incredible how much I've learned from you, thank you for taking the time to document all this info. I remember seeing the window air conditioners in my youth, usually between Albuquerque and El Paso.
I did hear some rather unpleasant distortion on the last video, especially with the 6K6. I attributed it to the camera mic or format compression. I also have never seem reverb on a scope. This is a big help to the homebrew camp. Thanks Doug and Jack! Jack is the worlds best amp scanner and champion of Hide and Seek!
Hi Doug! Thanks for a very interesting video on parasitic oscillation fuzzy worm . I used to work for GEC MRI (meters realy and instruments) here in Stafford, manufacturers of high voltage protection equipment . One of the main quality issues was wire placement of each wire or wire harness and had its own serial number and had a specific placement and wiring neighbours who it could get alongWith .This was to eliminate parasitic oscillation . On one occasion parasitic oscillation caused one of the built in computers to dump it's high voltage load could have had serious consequences and was just a simple wiring placement mistake error. That weather unbelievable !!!!!!! You got it made, great trucks, good weather. Doug your on a jolly ! Anyway thanks again. David UK Ps Very well noticed by one your viewers , you must attract smart People too. J
You're welcome, David, and thanks for your interesting and pleasant comments. Yes, our weather is exceptional, but getting a bit hot lately @ 104 degrees (in the shade......and there is no shade :) Jack and I think our viewers are the smartest and best on all of TH-cam.
Jack must be related to producer David Foster, who's often referred to the recording process as "shredding tape". Glad to see that you have idiosyncratic pets! I've heard of parasitic oscillation before, but it sounded dark, mysterious and uncommon. I'm amazed to see it in actual practice after all these years! Thank you so much, Uncle Doug, for clearing up this long-standing mystery.
Uncle Doug inspired me to build my own valve (tube) amps. These videos are so well done. To the point, informative, and fun to watch. Keep it up Uncle Doug, and watch out for Jack when he hides under the carpet.
Having just fought and won vs the worm on a recent amp build, using pretty much the same fix, it's great to see the theory behind it so eloquently and understandably explained. Another great vid Doug. Many thanks.
Very good video Uncle Doug... the importance of lead dress comes to pass here. You've shown an excellent way to narrow this down - thank you. amazing cars... amazing.
My apologies Doug, my attempts at humor are not always well received. I know your hard work deserves better than the brooking of someone like myself. You have certainly forgotten more than I will ever attempt to know in this area. Our beagle, sadly died of many things. She as I’m sure Rusty was to you, our canine child; I still forlorn her absence 2 years hence. Thank you for your hard work.
You're welcome, James. No apologies necessary. I enjoy your comments. The thought that animals may be able to detect the ultrasonic tone occurred to me too, and I definitely share your sorrow over a lost companion.
Duelling hands!! Ha ha! Love your crazy sense of humour. Very good example of how a scope can find problems not visible in any other way. I enjoy your two part presentations as the cars are stunning.
Very nice to see this explained and demonstrated on the oscilloscope! I found the 6K6 to have a little less drive on the signal and therefore smoother sounding with a touch more drip. The 6V6 seems to have more drive and covers up the drip some. Excellent video! Parasitic oscillation can also cause tubes to go into cutoff. I’ve experienced that before and lead dress was the issue one time and insufficient grid stoppers another time. Will have to try the oscilloscope as it makes it easy to see changes live.
Hello Uncle Doug! Finally getting caught up on your work. Excellent lesson and practical demonstration. I know you like the 6V6, but the more subtle tone of the 6K6 wins my vote. Great series!
Wow, that parasitic oscillation really ate the low end and bumped the highs a lot. With the lead dress adjustment I'm liking the 6K6 better for this application. Thanks for another great video, Uncle Doug!
Very well done, sir. A great surprise ending to a great series. Thank you for clarifying and correcting that, and for taking us through the troubleshooting process. Thanks to you and Jack for another great and worthwhile video.
Naturally I absolutely love your videos Doug. Every reverb amp I have owned had an articulate sound of a blonde yodeling in an Alpen Valley. They have always been the long Gibbs tank. For some reason your reverb unit sounds like an angry swarm of bees in a rock canyon. Almost like the the signal is being overwhelmed. My favorite hotrod? '32 five window highboy with flathead. Great video Doug!
Can’t tell you how much I love your videos Uncle Doug. Parasitic oscillation explained eloquently. Prefer the sound of the 6K6 personally. Jack the sticky tape muncher hilarious! Any vehicle with a blower floats my boat. Please keep them coming. Dropped everything once I saw a new video from you.
Great follow up! The oscilloscope does not lie! Seeing is believing. The Reverb unit has a lot of Reverb available. You may not need as much, but it is nice to have in case you do need it. Surf music! I still play Surf music. Great series! Just goes to show there is no end to tube amp investigation. Thanxz
Nice of you to make a video from one of your subs comments. There are some channels out there that will not help you if you ask-If I had money like I used to I would help but I just am not able to help anyone anymore. Some people will not respond anymore unless you send them money and I give you respect for not being that way.Thanks.
Usually us amateur radio ops deal with "parasitic oscillations" using RF amps, etc. sometimes causing catastrophic events, like a loud "boom 'n flash" that scares the crap out of you. Very interesting and I will re-check my HB 6G15 this weekend...keep up the great work Doug and nice truck vids...tell Jack HI !
Just fascinating! That’s why I enjoy your channel so much Uncle Doug, evidently your subscribers are some of the most intelligent 🤓 on TH-cam! I certainly learned something today, thank you for another super video. Buddy
You're welcome, Buddy. Jack and I think our viewers and subscribers are the best in the world......other than the small group of dolts who give some of our videos a thumbs-down ;)
Thanks so much!! I had built an amp, gone over it many many times, and it just wasn't sounding right. It had parasitic oscillations, and I moved one wire from the OT and fixed it!
@@UncleDoug I was hearing what I thought was a very harsh sound with with treble notes.....When you listed it in your symptoms, I said aha! Thanks again! You're a great teacher!
Very informative video Douglas. When I saw a number 1 by the side of the bell symbol, and saw it related to you, it immediately sparked my interest. Since seeing your last video, a question was left buzzing around inside my head. Here, I’m reminded of those pre-early 1970s television I learned to do servicing on. Lead dressing, and, in some instances, ensuring correct positioning of components (usually capacitors and/or inductors) onto a board could be critical. For example, vision styrations, and, exaggerated caption buzz etc, usually associated with the line time base often occurred. Or, in the case of valve radios, parasitic oscillations that caused motor boating, and strange background interference-like tones ...the types of effect that can be very difficult to realign out. When I saw the oscilloscope traces, they looked ‘corrupted’. I didn’t like saying anything since my field is radio, and television servicing, and not guitar amplifier servicing ...I’m sure you will agree with me when I say the two are different types of electronics animals. I’m glad someone pointed the parasitic oscillation fact out, and because of that you went on to produce this video. It has adequately addressed the question. Cheers, Phil.
Thanks for this vid, and the whole series on the reverb unit, Doug. I've got two Peavey tanks lying around, and I was looking for ideas for what to do with them. And thanks for this installment, specifically! When I saw that high-frequency waveform in the last vid, I was trying to figure out how just the reverb'd signal would result in such a thing. Glad to know i'm not quite as crazy as I previously thought. The whole revelation on parasitic oscillation was very enlightening. Like you said: one more reason to get an oscilloscope. Just wish they weren't so darned expensive!
BTW, the other reason I particularly enjoyed this vid is that I've been thinking a lot about tube-based oscillators, lately. Again, nicely enlightening on the concept.
Great learning/troubleshoot session! Now i can recognize oscillation as well :) Only need to buy someday a oscilloscope. Thanks again! And keep those beautiful cars coming ..
Wow UD, that was another great one! That thing looked dangerous. Maybe a flesh eater. If it got out of the scope, you'd need the other scope attached to a rifle. I'm glad you were able to subdue it before extreme measures were required. Cheers!
@@UncleDougHey UD! I know you are busy, and TH-cam land is glad for it. But I was just feeding a feral Momma & her five kittens out back of my apt and I stumbled across Cris Rea's 1989 Full Version of The Road to Hell. Had to go fetch the '81 Bullet Deluxe and do some strummin for the cats. But what struck me is that it sounds like he wrote it today before he left the building... Enjoy!
Once again, I'm watching your videos at 2:30am, and realising I've got problems with a number of amps that is most probably parasitical oscillation. Some I built myself, others custom built for the BBC no less! Darn it, now I need an oscilloscope! LOL
This is a very good thing to know, particularly knowing how easy it was to cause the oscillation. I don't think that this oscillation was enough to cause serious damage, but it was there and not noticeable to the ear.
I think it adversely affected the tone of the unit, particularly with the 6K6 tube......but you would probably never guess what the cause was without an oscilloscope.
Uncle Doug, Thank you for a very comprehensive viewing and analysis of your cloned CG15. All those time consuming start/stop, changes to the controls, guitar playing sections you did provided an excellent demonstration of the reverb effect. If I was asked to draw a picture of a signal waveform with reverb I would have been way off. Your oscilloscope views of parasitic oscillations, which were caused by such a deceptively simple thing, showed the value of such a device in diagnosing difficult faults. Then we get the hot rods and "Here's today's contender in the Holy shit award". Dry desert humour. Just Great. Regards, Jeff.
You're welcome, Jeff. I appreciate your kind comments and recognition of the many hours of work that go into making a video. I'm glad you enjoyed the video and hope that it was informative as well as entertaining.
I think you would have opened up a lot of peoples eyes with this video Uncle Doug.....and scope sales on Ebay will be going up lol.......I deal with a lot of parasitic's with the big transmitters I work on.....they are to be avoided at all costs........that first green truck was absolutely top notch....and that yellow blown job was awesome......just cant get enough of those machines.......a real credit to all their owners.
*Ultrasonic*, hypersonic means it's moving faster than Mach 4. ;) That's fantastic, Doug. I had a feeling something was wrong last time but couldn't quite put my finger on it. Thanks for clearing it up, figuratively and literally!
Capacitance, crosstalk interferance, and oscilloscopes! This sounds like the perfect lead in to analysys of phase shifters! Please Uncle Doug, how about a breakdown of the Small Stone or MXR Phase 90 four stage phase shifters? A remarkable effect produced by simple phase lag, and I suspect you would produce the best and most entertaining explanation and demonstration.
Thanks, M1. This is the first I have ever heard of them. Bear in mind that I work only on vintage tube amps, so I may not be the right guy for the job.
When we, as a group, fail in our active listening (to Jack), the ramifications can be unending and diverse. Sometimes what in hindsight we perceive as subtle clues may not be so subtle. Maybe it’s more complex to attune to Jack’s language of communication than it is to perceive and eliminate an electronic glitch. In all fairness to Jack, he intentionally refuses to do any sabre rattling when his signals are left unresponded to. A true genius in a whole new light!
Indeed, John. In the immortal words of Kierkegaard, "Ignoring Jack is like ignoring an oncoming freight train......yes, you may gain temporary peace, but at a staggering price". It sounds much better in the original Danish, but you get the idea.
very interesting. so the closeness of the wires from the plate and screen caused sympathetic electro-magnetic induction... point to point is more than art... good stuff.
Very interesting! I actually think I recall in the ElPaso TubeAmps video, he mentioned seeing a "carrier wave" on the wet signal during the oscilloscope test. I noticed a certain harshness on the previous tests, but figured it was just camera clipping. Maybe not, it sounds great now!
Yes, in a spectrum analysis of the output, there was an isolated hypersonic oscillation peak at around 25K as I recall. I'll bet the harshness was due to the oscillation.
from what im hearing dont get an overdrive pedal i was never tempted doug NEVER lol yeah i always thought you can do it much better with the right tubes & the amp will give you sweet overdrive.great post doug this series is like finding treasure for the true reverb hound regards jamie..
My YT account pushed up this video serie as "recommended" and unseen yet... And it's a pleasure to watch again. And to give a thumbs up, better late than not. I watch the scope : the (1kHz) cycle stretch over 5 square on the screen. I count 7 or 8 spike (or hair of fuzz) in each square. So the parasitic oscillation frequency is about 35-40 kHz! Inaudible for men (But Rusty may have heard hit, dog bandwidth is about 70 to 45000 Hz) but low enough to produce intermodulation distortion, wich typically is not the kind of distortion you want even in a electric guitar rig, the distortion being not harmonically related to the signal. edit: with other tubes the freq. seem a little less (25-30kHZ) and the 'fuzz' look cleaner. Very interresting. This scope musings remind me of my high school years...
Yes, indeed, AS......the oscillation was above the range of human hearing (most frequencies are above my wretched hearing), so without a scope it was virtually undetectable.
A salute to the ol' boy who spotted the oscillation problem...Lord knows I wasn't paying attention(8-). Anyway, all is great when we get to learn something new. Thanks for sharing, Uncle Doug. Hard to tell a difference twixt the 6V6 and the 6K6 from here...but I think the 6V6 would be my pick too. Man, Doug...you know where all the cool iron is displayed(8-). Not all of them are done to my tastes either, but I think it's better to have something for everyone anyway...
Amen, Tom. Viewers are a great source of information and add a lot to a channel, especially if you take the time to read and pay attention to the comments.....as I always try to do.
Yeah...ya sit there scratchin' yer head thinkin', "What's wrong with this picture...?" Then someone taps you on the shoulder and sez, "Whoa! Looks like that circuit was designed by a fella named A. B. Normal." What do you figure the oscillation frequency was, Doug? Even if there were 25 oscillation cycles per every one from your generated signal, that would make 25k. When I was a real young buck, I could hear 15.750kc flyback from a TV...but I could never hear 25kc.
I am a physician (I am) and have never seen (I have) a case of, say... Wallenberg Syndrome. Am I that bad because in almost forty years not a single case has come to me to diagnose it? You may say you're 100 years old and have seen everything and be wrong. On the other hand, a freshly graduated physician could've seen one case and be considered "the best". As we are always teaching, we are always learning. That's the beauty of knowledge. Keep spreading it. Cheers!
A fine example of this principle is the Tacoma Narrows Bridge failure. The constructive interference, induced by the wind, caused the structure to oscillate to the point of failure. Of course, there are youtube videos of the bridge failure. You have many times cautioned us about how different signals could cross-talk. Leave that fuzzy worm for the bottom of the tequilla bottle.
I recall hearing about the avoidance of harmonic vibration within bridges, CK, and have definitely learned a lesson from this experience. Amen on the worm :)
Excellent job finding a way to cure the parasitic oscillation by moving wires. If it was me, I would have tried to bundle the wires together again and use a stopper resistor for the screen grid near the tube and see if that would work. If so leave it there at the smallest value that will work, and then separating the wires again. That would give some extra margin.
Thanks Doug, I assume you are contemplating putting your collection of DIY amps through the oscilloscope to check for this problem now you know what you are looking for in the trace output. It would make a good video on 'Rules for good lead dress" I think.
You're welcome, Allan. Not just my home-built amps, but all amps.....since they are all susceptible to the problem. If I find any more similar issues, I'll describe them in a video.
this was very interesting i must say.. and shows that information is a never ending source. And btw in part 3 i liked the 6v6 the best. But now the 6k6 sounds moore articulate. Greate video.. realy greate. 😀
The parasitic oscillation was working like the regeneration control on the old radios. You adjusted it to amplify the signal and stopped before it went into oscillation.
This was very informative. Thanks mucho! Darn oscillation! I got a high frequency (very audible) when I 'forgot' to ground one of the speaker connections...
Oi , tuck yer shirt in , lol.. and I like that zingy tube reverb that transistors cant quite make . well done too . You didn't quite get to the grid resistor , but I put 10 K ohm on everything i build . I'll be watching my lead dress too , after seeing this top notch video too. Thanks Doug ..
@ 19:49 as per 12:20! I don't have an oscilloscope because I don't know how to use one ... well that is going to change! As soon as I can afford one! LOL @ 22:27 Marilyn Monroe ? Thanks Uncle Doug!
On one of your other videos, you put a capacitor across the reverb tank output to kill of the wobbly, oscillating of the spring, as Fender did on a circuit revision. So your reverb could sound even smoother! :o)
The cars look incredible, Here in the UK we have the Tatton Park classic car show this weekend , brilliant cars might be worth a "Google" search to see what enthusiasts do here Uncle Doug
Thanks. A Facebook viewer sent me some photos, S-D, and the vehicles were exceptionally nice. It's great to see that these old gems have international appreciation.
Thank you. It is always great when someone has an oversight, or made a mistake, acknowledges it and fix it. We need more people like you.
You're welcome, RED. I thought it was an excellent opportunity to learn about a rather elusive topic.
I'm a simple man. When I see Uncle Doug uploaded a new video, I give it a like.
You're not simple, Kley, you're a discriminating viewer with exceptionally good taste :) Thanks !!!
Moi Aussie bien sur
We still love you Uncle Doug
I hope so, Mr. T :)
I love that someone as knowledgeable as you is still learning new things and open enough to talk about it. another great video... appreciate being able to learn with you!
Thanks, Joe. I'm a strong believer in the old "use it or lose it" philosophy when it comes to learning.....and you should never stop sharing what you know with others.
What I appreciated most I think was the solution and the method of finding the source of it. As a teenager hobbyist I was implored to fix a red plate output stage on a rather powerful Bass amp. Shook my head and said I would if I knew what was going on there. Now I think I do, thanks for closing such circles for me.
You're welcome, Lee. I think as our lives progress and we gain more and more experience with all things, including electronics snafu's, there is a snowball effect.....gathering mass (knowledge) as we progress. I'm glad that our videos have aided your progress.
I recently read an article addressing point to point, turret board and pcb wiring schemes that explains the pros and cons. The overwhelming similarity was how important it was to pay attention to lead dress and or lay out due to the very thing you found here. I am glad I read that article prior to me building my amp to avoid frustrations. Thank you again for all these videos. Absolutely priceless information and your teaching approach is top notch for me.
Thanks so much, Kevin. You make an excellent point about lead dress, it can make or break an amp circuit.
I just keep finding more excellent video's on your channel.
Car show; In high school, I found a half ton, 1948, 5 window or wraparound window Chevrolet with a perfect chrome front grill, outside windshield visor, the tranny was out, I believe it had a 235 or smaller straight 6 engine, but everything down to the faded green paint was original, nary a scratch on it just sitting there parked next to a shed.
I aquired it for $125 and dad sold it to a collector for ?
LoL
I used to find classic vehicles like a bird dog bringing up pheasants when I was young. I always told him that we should sit on them for at least twenty years and then sell them at a greater profit and keep a few for ourselves, but he was always happy with an extra $500. He lived for the moment and that was it.
Thanks again, Cheers!
Too bad dad didn't listen to you, Amo. You were right.
Just another example of the adage “we are never too old to learn”. I kept thinking something was just odd about that waveform, but having never looked at an output of a reverb tank it didn’t dawn on me that the high frequencies in that 1K sine wave would be hypersonic or up to RF. That’s why I love working with electronics, just when you thought you had a good grasp on how a circuit was supposed to operate, a gremlin pops up. Back in my 800 MHz trunking two way radio tech days, I used to tell customers that “theoretically that radio can’t do what you have told me it did, but you anything is possible with electronics”. At the car show, you apparently have a friend that has taken OCD to an absolutely beautiful art form. The details on that 5 window pickup were perfection. Precise hose and cable routing and a perfect firewall, not full of holes or patched over holes, WOW.
Amen, Mark. The car-builder/friend is indeed quite skilled :)
A simple fix for a big problem. Another lesson, you couldnt tell there was a problem until something burn later. Unless you had it on the oscilloscope before calling it done! Again, beautiful build. Thanks for sharing.
You're welcome, Daniel. Quite true......without an oscilloscope, the problem is virtually impossible to detect.
First, very nice work with whoever called out the parasitic oscillation. It was a very remarkable interior. Second, on the car show segment, the El Camino showed us as much of your exterior as we will probably ever see in the reflection in the window glass. It didn't shatter, and your superhero identity and look is still hidden for the most part.
I agree, Joel. Viewer input is a valuable resource. I guess I'll have to wear a costume while making videos of shiny cars.....perhaps a fake beard and dreadlocks.
That was a great, great project to begin with, but the parasitic oscillation and how to find and eliminate it was a true cherry on top of it. Call me a nerd, but I really like it when some problem-solving is required, and a spiffy problem-solving you provided. Very well done, in all aspects of the project - congrats!
Thanks so much, KL. I appreciate your kind appraisal of the video, and am glad that you found it to be helpful and informative.
Hey I got the notification this time! I never got one for the last video. I only knew you had uploaded it because it showed up in the sidebar of suggested videos.
Man I am so glad you are doing videos again! Some of my favorite content on TH-cam.
That's good news, TJ. Thanks so much :)
The post-repair audio sounds a lot better to me. Nice video.
Thanks, Bill :)
It does, and now the 6K6 sounds better has the 6V6 or whatever it was. It would be interesting to know how much loss there is through the reverb unit, i.e how much gain needs to be made up before and after.
What a wonderful Jack, and wonderful oscillation and EMI explenation.
Thanks so much, Sarah. We hope you enjoyed it.
"Not to my taste, but impressive workmanship". I'm heavy into your informative videos of late, sir, and this statement is a great example of the wisdom you dispense. Seems mandatory to have such an open-minded, but grounded, outlook where serious voltages are concerned. Thank you.
Thanks, Ro. We appreciate it. You're welcome.
Awesome job, with all your knowledge and years of experience there was still something for you to learn and what is even more impressive is that you owned it and did not make any excuses. It takes a very secure person to do something like that, the world needs more people like you. To top everything off you were kind of enough to share this learning experience with us, my hats off to you sir. Again thank you for your channel and sharing your knowledge with us.
You're quite welcome, Michael, and I sincerely appreciate your analysis of the situation. Learning opportunities are far more important that petty pride.....and If I've never seen a phenomenon before, then it's quite likely that the majority of viewers have never seen it either. This channel isn't something I do for you all. It's something we do together.
It's incredible how much I've learned from you, thank you for taking the time to document all this info. I remember seeing the window air conditioners in my youth, usually between Albuquerque and El Paso.
You're welcome, Andrew. Those old window coolers were great on long, straight roads......but hell in the turns :)
I did hear some rather unpleasant distortion on the last video, especially with the 6K6. I attributed it to the camera mic or format compression. I also have never seem reverb on a scope. This is a big help to the homebrew camp.
Thanks Doug and Jack! Jack is the worlds best amp scanner and champion of Hide and Seek!
You're welcome, Matt. I'm glad the video was helpful.
Hi Doug!
Thanks for a very interesting video on parasitic oscillation fuzzy worm .
I used to work for GEC MRI (meters realy and instruments) here in Stafford, manufacturers of high voltage protection equipment . One of the main quality issues was wire placement of each wire or wire harness and had its own serial number and had a specific placement and wiring neighbours who it could get alongWith .This was to eliminate parasitic oscillation . On one occasion parasitic oscillation caused one of the built in computers to dump it's high voltage load could have had serious consequences and was just a simple wiring placement mistake error.
That weather unbelievable !!!!!!! You got it made, great trucks, good weather. Doug your on a jolly !
Anyway thanks again.
David UK
Ps
Very well noticed by one your viewers , you must attract smart People too.
J
You're welcome, David, and thanks for your interesting and pleasant comments. Yes, our weather is exceptional, but getting a bit hot lately @ 104 degrees (in the shade......and there is no shade :) Jack and I think our viewers are the smartest and best on all of TH-cam.
Jack must be related to producer David Foster, who's often referred to the recording process as "shredding tape". Glad to see that you have idiosyncratic pets!
I've heard of parasitic oscillation before, but it sounded dark, mysterious and uncommon. I'm amazed to see it in actual practice after all these years! Thank you so much, Uncle Doug, for clearing up this long-standing mystery.
Jack is a shredder from way back, Dave :) You're welcome.
Really glad that you explored this parasitic oscillation and demonstrating unwanted capacitance from nearby wires Wow, great video !
Glad it was helpful, JJ.
Uncle Doug inspired me to build my own valve (tube) amps. These videos are so well done. To the point, informative, and fun to watch. Keep it up Uncle Doug, and watch out for Jack when he hides under the carpet.
Thanks, Z, for your very kind comments. I will :)
Love your videos Uncle Doug, glad you're back.
We're glad to be back, TC. Thanks !!
Well, live und learn...
Thanks for sharing the problem and the fix. You keep living and I'll keep learning!
Will do, Joseph.
Hats off for my favorite uncle.
I learn so much from watching ur videos. You explain things in such a way a novise like me can follow along.
Thanks, Boogie. That's great to hear :)
Having just fought and won vs the worm on a recent amp build, using pretty much the same fix, it's great to see the theory behind it so eloquently and understandably explained. Another great vid Doug. Many thanks.
You're welcome, Steve. I'm glad you were successful in vanquishing the fuzzy little guy :) Thanks !!
Very good video Uncle Doug... the importance of lead dress comes to pass here. You've shown an excellent way to narrow this down - thank you. amazing cars... amazing.
You're welcome, Ron. I'm glad the video was helpful :)
My apologies Doug, my attempts at humor are not always well received. I know your hard work deserves better than the brooking of someone like myself. You have certainly forgotten more than I will ever attempt to know in this area.
Our beagle, sadly died of many things. She as I’m sure Rusty was to you, our canine child; I still forlorn her absence 2 years hence.
Thank you for your hard work.
You're welcome, James. No apologies necessary. I enjoy your comments. The thought that animals may be able to detect the ultrasonic tone occurred to me too, and I definitely share your sorrow over a lost companion.
Duelling hands!! Ha ha! Love your crazy sense of humour. Very good example of how a scope can find problems not visible in any other way. I enjoy your two part presentations as the cars are stunning.
Thanks, TT.....glad you enjoyed it :)
Nicely done UncleDone, Once again made it crystal clear. great video.
Thanks, Eddie :)
Very nice to see this explained and demonstrated on the oscilloscope! I found the 6K6 to have a little less drive on the signal and therefore smoother sounding with a touch more drip. The 6V6 seems to have more drive and covers up the drip some. Excellent video! Parasitic oscillation can also cause tubes to go into cutoff. I’ve experienced that before and lead dress was the issue one time and insufficient grid stoppers another time. Will have to try the oscilloscope as it makes it easy to see changes live.
Thanks for your input, Trem.
Love your video's! Hypersonic: faster than sound. Ultrasonic: above human hearing.
Then ultrasonic is it.....thanks, M84 :)
Hello Uncle Doug! Finally getting caught up on your work. Excellent lesson and practical demonstration. I know you like the 6V6, but the more subtle tone of the 6K6 wins my vote. Great series!
Thanks, JC. A lot of viewers shared your preference for the 6K6.
Thanks for sharing this, Uncle Doug, & please thank your viewer, who pointed it out, as there are a lot of wiser people now.1428 as I watched.
You're welcome, Jack. The viewers are a valuable resource and often provide significant insight and suggestions. We all can benefit from their input.
Wow, that parasitic oscillation really ate the low end and bumped the highs a lot. With the lead dress adjustment I'm liking the 6K6 better for this application. Thanks for another great video, Uncle Doug!
You're welcome, KC. Thanks for your input.
Very well done, sir. A great surprise ending to a great series. Thank you for clarifying and correcting that, and for taking us through the troubleshooting process. Thanks to you and Jack for another great and worthwhile video.
You're quite welcome, OM. Thanks !!
Naturally I absolutely love your videos Doug.
Every reverb amp I have owned had an articulate sound of a blonde yodeling in an Alpen Valley. They have always been the long Gibbs tank.
For some reason your reverb unit sounds like an angry swarm of bees in a rock canyon. Almost like the the signal is being overwhelmed.
My favorite hotrod? '32 five window highboy with flathead.
Great video Doug!
Thanks, KM :)
Can’t tell you how much I love your videos Uncle Doug. Parasitic oscillation explained eloquently. Prefer the sound of the 6K6 personally. Jack the sticky tape muncher hilarious! Any vehicle with a blower floats my boat. Please keep them coming. Dropped everything once I saw a new video from you.
Thanks, Iceman.......glad you enjoyed it :)
I just loved this "correction" video as well as the whole series. And I learned something new. Thanks!
You're welcome, Fabio. I think both of us learned a valuable lesson.....which is always a good thing :)
This was fantastic. The TH-cam world pitching in to help solve a problem. I love it! The blue and silver truck looks pretty amazing.
Thanks, SS. I agree.....the viewers came through with the expertise to resolve the issue.
Great follow up! The oscilloscope does not lie! Seeing is believing. The Reverb unit has a lot of Reverb available. You may not need as much, but it is nice to have in case you do need it. Surf music! I still play Surf music. Great series! Just goes to show there is no end to tube amp investigation. Thanxz
You're welcome, ATL. Yes, the reverb output can be excessive with either tube, but what a nice excess to have available :)
25:05 "Oh shit, Holstein!" ;)
Nice easy fix of the reverb unit and a lot of nice cars again, thanks Uncle Doug!
You're welcome, Tocsa :)
Nice of you to make a video from one of your subs comments. There are some channels out there that will not help you if you ask-If I had money like I used to I would help but I just am not able to help anyone anymore. Some people will not respond anymore unless you send them money and I give you respect for not being that way.Thanks.
You're welcome, WN. Thanks !!!
Excellent. I've always wanted to know more about oscillation, particularly what it looks like on an oscilloscope. Thanks.
Glad it was helpful, Carl :)
Uncle doug best on youtube.
Thanks so much, LF. You are too kind :)
Damn Doug... if you keep this up I might actually begin to understand electronics. Again, another example of your excellent approach to electronics.
Thanks so much, Bill :)
Usually us amateur radio ops deal with "parasitic oscillations" using RF amps, etc. sometimes causing catastrophic events, like a loud "boom 'n flash" that scares the crap out of you. Very interesting and I will re-check my HB 6G15 this weekend...keep up the great work Doug and nice truck vids...tell Jack HI !
Yes, indeed, Tom.....the results of an untreated worm infestation could be rather dramatic. Thank heavens for vigilant viewers.
Just fascinating! That’s why I enjoy your channel so much Uncle Doug, evidently your subscribers are some of the most intelligent 🤓 on TH-cam! I certainly learned something today, thank you for another super video. Buddy
You're welcome, Buddy. Jack and I think our viewers and subscribers are the best in the world......other than the small group of dolts who give some of our videos a thumbs-down ;)
Thanks so much!! I had built an amp, gone over it many many times, and it just wasn't sounding right. It had parasitic oscillations, and I moved one wire from the OT and fixed it!
PO's are tough to detect without an oscilloscope......but generally fairly easy to fix.
@@UncleDoug I was hearing what I thought was a very harsh sound with with treble notes.....When you listed it in your symptoms, I said aha! Thanks again! You're a great teacher!
@@aaroneisenstein4663 You're welcome, Aaron. Glad it was helpful.
Nice learning moment for us all...Thanks Doug
You're welcome, Lee.
Absolutely top notch professional.
Thanks so much, G :)
Very informative video Douglas.
When I saw a number 1 by the side of the bell symbol, and saw it related to you, it immediately sparked my interest. Since seeing your last video, a question was left buzzing around inside my head.
Here, I’m reminded of those pre-early 1970s television I learned to do servicing on. Lead dressing, and, in some instances, ensuring correct positioning of components (usually capacitors and/or inductors) onto a board could be critical. For example, vision styrations, and, exaggerated caption buzz etc, usually associated with the line time base often occurred. Or, in the case of valve radios, parasitic oscillations that caused motor boating, and strange background interference-like tones ...the types of effect that can be very difficult to realign out.
When I saw the oscilloscope traces, they looked ‘corrupted’. I didn’t like saying anything since my field is radio, and television servicing, and not guitar amplifier servicing ...I’m sure you will agree with me when I say the two are different types of electronics animals.
I’m glad someone pointed the parasitic oscillation fact out, and because of that you went on to produce this video. It has adequately addressed the question.
Cheers, Phil.
Thanks for your knowledgeable and helpful input, Phil :)
Thanks for this vid, and the whole series on the reverb unit, Doug. I've got two Peavey tanks lying around, and I was looking for ideas for what to do with them.
And thanks for this installment, specifically! When I saw that high-frequency waveform in the last vid, I was trying to figure out how just the reverb'd signal would result in such a thing. Glad to know i'm not quite as crazy as I previously thought. The whole revelation on parasitic oscillation was very enlightening. Like you said: one more reason to get an oscilloscope. Just wish they weren't so darned expensive!
BTW, the other reason I particularly enjoyed this vid is that I've been thinking a lot about tube-based oscillators, lately. Again, nicely enlightening on the concept.
You're welcome, Ed. It's great to hear that the video was helpful :)
Great learning/troubleshoot session! Now i can recognize oscillation as well :) Only need to buy someday a oscilloscope. Thanks again! And keep those beautiful cars coming ..
Thanks, Sebastiaan. I'm glad the video was helpful.
Wow UD, that was another great one! That thing looked dangerous. Maybe a flesh eater. If it got out of the scope, you'd need the other scope attached to a rifle. I'm glad you were able to subdue it before extreme measures were required. Cheers!
Thanks, FW :)
@@UncleDougHey UD! I know you are busy, and TH-cam land is glad for it. But I was just feeding a feral Momma & her five kittens out back of my apt and I stumbled across Cris Rea's 1989 Full Version of The Road to Hell. Had to go fetch the '81 Bullet Deluxe and do some strummin for the cats. But what struck me is that it sounds like he wrote it today before he left the building... Enjoy!
Thank you very much! ... this video series I found to be so educational and fun!
You're welcome, Carlos. Glad you enjoyed it :)
If Rusty the Wonder God had been around he would certainly have heard the parasitic worm and alerted us all! (thanks for another great vid UD)
No doubt, RF. He would have howled like a banshee whenever the hypersonic oscillation tickled his tympanic membranes :) You're welcome.
Once again, I'm watching your videos at 2:30am, and realising I've got problems with a number of amps that is most probably parasitical oscillation. Some I built myself, others custom built for the BBC no less! Darn it, now I need an oscilloscope! LOL
Oscilloscopes do have specific applications that cannot be accomplished by any other means.....so I guess your stuck buying one :)
Another great educational presentation! Thank you!
You're welcome, K1 :)
This is a very good thing to know, particularly knowing how easy it was to cause the oscillation. I don't think that this oscillation was enough to cause serious damage, but it was there and not noticeable to the ear.
I think it adversely affected the tone of the unit, particularly with the 6K6 tube......but you would probably never guess what the cause was without an oscilloscope.
Uncle Doug, Thank you for a very comprehensive viewing and analysis of your cloned CG15. All those time consuming start/stop, changes to the controls, guitar playing sections you did provided an excellent demonstration of the reverb effect. If I was asked to draw a picture of a signal waveform with reverb I would have been way off. Your oscilloscope views of parasitic oscillations, which were caused by such a deceptively simple thing, showed the value of such a device in diagnosing difficult faults. Then we get the hot rods and "Here's today's contender in the Holy shit award". Dry desert humour. Just Great. Regards, Jeff.
You're welcome, Jeff. I appreciate your kind comments and recognition of the many hours of work that go into making a video. I'm glad you enjoyed the video and hope that it was informative as well as entertaining.
This has got me thinking about some issues I've been having recently with a Dynaco amp. Thanks again for the great informative videos.
You're welcome, MtB :)
I think you would have opened up a lot of peoples eyes with this video Uncle Doug.....and scope sales on Ebay will be going up lol.......I deal with a lot of parasitic's with the big transmitters I work on.....they are to be avoided at all costs........that first green truck was absolutely top notch....and that yellow blown job was awesome......just cant get enough of those machines.......a real credit to all their owners.
Thanks, Harb. I really hope that the video is as informative to viewers as it was to me :)
*Ultrasonic*, hypersonic means it's moving faster than Mach 4. ;) That's fantastic, Doug. I had a feeling something was wrong last time but couldn't quite put my finger on it. Thanks for clearing it up, figuratively and literally!
Whatever sonic it was, it was potentially bad news, AQ......and we're better off without its fuzzy little presence :) You're welcome.
Definitely!
Capacitance, crosstalk interferance, and oscilloscopes! This sounds like the perfect lead in to analysys of phase shifters! Please Uncle Doug, how about a breakdown of the Small Stone or MXR Phase 90 four stage phase shifters? A remarkable effect produced by simple phase lag, and I suspect you would produce the best and most entertaining explanation and demonstration.
Thanks, M1. This is the first I have ever heard of them. Bear in mind that I work only on vintage tube amps, so I may not be the right guy for the job.
That was really interesting. I'm glad you got your reverb dewormed.
Thanks, _N. So am I.....the fuzzy worm was beginning to chafe a bit :)
Great video. I once again had an opportunity to learn something new :)
So did I, Tom :)
When we, as a group, fail in our active listening (to Jack), the ramifications can be unending and diverse. Sometimes what in hindsight we perceive as subtle clues may not be so subtle. Maybe it’s more complex to attune to Jack’s language of communication than it is to perceive and eliminate an electronic glitch. In all fairness to Jack, he intentionally refuses to do any sabre rattling when his signals are left unresponded to. A true genius in a whole new light!
Indeed, John. In the immortal words of Kierkegaard, "Ignoring Jack is like ignoring an oncoming freight train......yes, you may gain temporary peace, but at a staggering price". It sounds much better in the original Danish, but you get the idea.
I'm pretty sure that Rusty would have detected that hypersonic parasitic oscillation.
He probably would have howled like whenever he hears a distant ambulance :)
@@UncleDoug Come on ,guys. You’re making me miss my old dog and Rusty both!
@@williambock1821 me too brother, Sadie chocolate lab
very interesting. so the closeness of the wires from the plate and screen caused sympathetic electro-magnetic induction... point to point is more than art... good stuff.
Actually, it was the proximity of the plate wire to the very sensitive Dwell control wires that created the positive feedback, Tony.
very interesting. thank you so much for this usefull information. also the car show. and Jacks demostration. Thanks Doug.
You're welcome, Jason :)
wow means alot takes everything in a diff perspective nice job Uncle Doug just wowsa thinking about my ampeg now
Thanks, Joe :)
Very interesting! I actually think I recall in the ElPaso TubeAmps video, he mentioned seeing a "carrier wave" on the wet signal during the oscilloscope test. I noticed a certain harshness on the previous tests, but figured it was just camera clipping. Maybe not, it sounds great now!
Yes, in a spectrum analysis of the output, there was an isolated hypersonic oscillation peak at around 25K as I recall. I'll bet the harshness was due to the oscillation.
from what im hearing dont get an overdrive pedal i was never tempted doug NEVER lol yeah i always thought you can do it much better with the right tubes & the amp will give you sweet overdrive.great post doug this series is like finding treasure for the true reverb hound regards jamie..
I agree, Jamie. Overdrive pedals really stress the circuit....especially the output transformer, which will get so hot you can cook eggs on it.
My YT account pushed up this video serie as "recommended" and unseen yet...
And it's a pleasure to watch again. And to give a thumbs up, better late than not.
I watch the scope : the (1kHz) cycle stretch over 5 square on the screen. I count 7 or 8 spike (or hair of fuzz) in each square.
So the parasitic oscillation frequency is about 35-40 kHz! Inaudible for men (But Rusty may have heard hit, dog bandwidth is about 70 to 45000 Hz) but low enough to produce intermodulation distortion, wich typically is not the kind of distortion you want even in a electric guitar rig, the distortion being not harmonically related to the signal.
edit: with other tubes the freq. seem a little less (25-30kHZ) and the 'fuzz' look cleaner. Very interresting. This scope musings remind me of my high school years...
Yes, indeed, AS......the oscillation was above the range of human hearing (most frequencies are above my wretched hearing), so without a scope it was virtually undetectable.
A salute to the ol' boy who spotted the oscillation problem...Lord knows I wasn't paying attention(8-).
Anyway, all is great when we get to learn something new. Thanks for sharing, Uncle Doug.
Hard to tell a difference twixt the 6V6 and the 6K6 from here...but I think the 6V6 would be my pick too.
Man, Doug...you know where all the cool iron is displayed(8-). Not all of them are done to my tastes
either, but I think it's better to have something for everyone anyway...
Amen, Tom. Viewers are a great source of information and add a lot to a channel, especially if you take the time to read and pay attention to the comments.....as I always try to do.
Yeah...ya sit there scratchin' yer head thinkin', "What's wrong with this picture...?" Then someone
taps you on the shoulder and sez, "Whoa! Looks like that circuit was designed by a fella named
A. B. Normal." What do you figure the oscillation frequency was, Doug? Even if there were 25
oscillation cycles per every one from your generated signal, that would make 25k. When I was
a real young buck, I could hear 15.750kc flyback from a TV...but I could never hear 25kc.
Wow i love those old cars and trucks.
I'm glad, Denver. Welcome to our channel.
Great video Uncle Doug. 👍🏼👍🏼
Thanks so much, RH. It's good to hear from you :)
Love all the American Graffiti cars at the show.
I'm glad, Rob. Thanks for joining us :)
I am a physician (I am) and have never seen (I have) a case of, say... Wallenberg Syndrome. Am I that bad because in almost forty years not a single case has come to me to diagnose it? You may say you're 100 years old and have seen everything and be wrong. On the other hand, a freshly graduated physician could've seen one case and be considered "the best". As we are always teaching, we are always learning. That's the beauty of knowledge. Keep spreading it. Cheers!
Well said, PK. Will do.
Thanks for another great video, Doug! Looking forward to the new ones!
You're welcome, Delatsch
I noticed the reverb was better after the repair...your playing is sounding great....hope your not hurting too much
Thanks, Ivan. I've been taking it easy on the old hands, and they seem to be feeling a little better.
A fine example of this principle is the Tacoma Narrows Bridge failure. The constructive interference, induced by the wind, caused the structure to oscillate to the point of failure. Of course, there are youtube videos of the bridge failure.
You have many times cautioned us about how different signals could cross-talk.
Leave that fuzzy worm for the bottom of the tequilla bottle.
I recall hearing about the avoidance of harmonic vibration within bridges, CK, and have definitely learned a lesson from this experience. Amen on the worm :)
No worms live in tequila... they're found in some mescals instead.
Fabulous Doug... Now I like the 6k6... a tad more subtle but I think it better facilitates the "classic Fender drip" and tone ...
Also I think the 6k6 is clearer...
Thanks for your input, Michael. Glad you liked the de-wormed 6K6 :)
6k6 sounds less harsh i think :) great vid! excellent info Thankyou Uncle Doug!!!
You're welcome, DF.
Excellent job finding a way to cure the parasitic oscillation by moving wires. If it was me, I would have tried to bundle the wires together again and use a stopper resistor for the screen grid near the tube and see if that would work. If so leave it there at the smallest value that will work, and then separating the wires again. That would give some extra margin.
That's an excellent suggestion, A. Thanks !!!
That was super eye-opening. How many otherwise great amps burned themselves
up only because of `poor wiring techniques`
Love your car shows. If one day i find a pretty penny, i might show up to see what kind of deal i could scare up. lol
Thanks, Lee. It's a very elusive problem that causes all sorts of harm. I hope this helped to clarify the issue.
Thanks Doug, I assume you are contemplating putting your collection of DIY amps through the oscilloscope to check for this problem now you know what you are looking for in the trace output. It would make a good video on 'Rules for good lead dress" I think.
You're welcome, Allan. Not just my home-built amps, but all amps.....since they are all susceptible to the problem. If I find any more similar issues, I'll describe them in a video.
this was very interesting i must say.. and shows that information is a never ending source. And btw in part 3 i liked the 6v6 the best. But now the 6k6 sounds moore articulate.
Greate video.. realy greate. 😀
Thanks, Dr. Z :)
Great great great! Thank's Doug!
You're welcome, Rob :)
LOL, I was going to pass on building this someday after Part 3. Sounds like exactly what I want now!
Good luck with your build, Mike.
The parasitic oscillation was working like the regeneration control on the old radios. You adjusted it to amplify the signal and stopped before it went into oscillation.
Thanks, Ruff :)
This was very informative. Thanks mucho! Darn oscillation! I got a high frequency (very audible) when I 'forgot' to ground one of the speaker connections...
You're welcome, John.......glad it was helpful.
Never heard of that so another good schooling on this one. Thanks Doug for another great eye opener. Scratch Jack's head for me ...
You're welcome, Carl. I will :)
Oi , tuck yer shirt in , lol.. and I like that zingy tube reverb that transistors cant quite make . well done too .
You didn't quite get to the grid resistor , but I put 10 K ohm on everything i build . I'll be watching my lead dress too , after seeing this top notch video too. Thanks Doug ..
You're welcome, Steven. Grid blockers are a good idea :)
Quality stuff,sir. Thanks for the life enriching content😃
You're welcome, Ken.
@ 19:49 as per 12:20! I don't
have an oscilloscope because I
don't know how to use one ...
well that is going to change!
As soon as I can afford one! LOL
@ 22:27 Marilyn Monroe ?
Thanks Uncle Doug!
It's a great instrument for diagnostic purposes, Wayne. God only knows who or what served as the model for that enchanting portrait :)
Thanks for sharing
You're welcome, Jason.
On one of your other videos, you put a capacitor across the reverb tank output to kill of the wobbly, oscillating of the spring, as Fender did on a circuit revision. So your reverb could sound even smoother! :o)
That sounds familiar, Prince :)
The cars look incredible, Here in the UK we have the Tatton Park classic car show this weekend , brilliant cars might be worth a "Google" search to see what enthusiasts do here Uncle Doug
Thanks. A Facebook viewer sent me some photos, S-D, and the vehicles were exceptionally nice. It's great to see that these old gems have international appreciation.