To learn electronics in a very different and effective way, and gain access to Mr Carlson's personal designs and inventions, visit the Mr Carlson's Lab Patreon page here: www.patreon.com/MrCarlsonsLab
10 minutes explaining how to clean a switch is a good indicator how serious you take these things. And it seems you love you work/hobby. Great! Thanks for all your videos.
Glad I voted for restoring this receiver. I'm learning a lot plus it's interesting to see the effort the design engineers put into this product. It's definitely not a throw away consumer item.
The two things that made me happiest about this video: 1.} Your bench was a little bit messy from doing all the work. 2.} You got all the way to the end and found out you had a bad output transformer. You are human after all. Ha. That exact thing happened to me on a Grunow Teledial radio. The only difference was I didn't have one just laying around. I had to buy a speaker with one mounted to it and switch it over. Thanks for the series. Loving it.
Thanks a lot! I love this series. You've managed to bring back "the good old days" feeling of your old videos with the new lab and updated equipment and other improvements. I love having the HP nixie tube meter and the vfd display in the Agilent meter in the shot at the same time. (in case you can't decide which you like better, you're covered!)
You really have a way of talking that makes me never get bored of it even though most of your videos aren't short and I don't understand half of what you're doing 😄 And what really intrigues me is how you can work in a place that is always clean and tidy, I don't do a quarter of what you do and I work in a place like a war zone 😂
Today I learned that resistors can be noisy... I wish I had room in my life for another expensive hobby, I'd be diving right in buying equipment and supplies... and Mr. Carlson's training materials! I'll have to satisfy myself with the occasional video, alas, but I'm very happy to know that there's people out there keeping all this old gear working and living on into the 21st Century.
Am presently working on a 60 year old admiral small console record player that uses a 12ax7 and two 50c5 tubes in a push pull arrangement. 4N2A amplifier. Every time I think I'm close to finished I watch one of your videos start checking the numerous other things. you talk about. I don't want to do any damage to the unit by playing too much.
Superb tutorial as ever! I learnt a lot. Thanks. I wasn't previously aware of diode valve limitations "soft rectifiers" etc. - I wonder if ElectroBoom knows.... Looking forward to the next installment!
I think one of the more important points that you made in this video is lubricating the shafts of potentiometers, and rotary switches,, I have spent many hours freeing up stuck shafts on those devices,,, :-)
This was awesome! Just finished watching this one today. I am definitely going to go over it again with a note book as you suggested. There is so much wisdom in how you so things. Thanks for an awesome video.
There isn't anyone who is as thorough as YOU! I'm very interested in the identification of which lead is connected to capacitor's "outter foil." Others seem very uninterested in this critical noise reduction technique. Why? It isn't that difficult to implement! ALSO was 'educated' myself about noisy resistors. That could be maddening! Didn't know about that test? Would noise appearbon scope of a powered up unit but with no input?
The answer is very simple Tom. The reason they deny it is: They have been doing it wrong for years, then they find it hard to admit and come too terms with that. If you can see an electrical difference (a very pronounced difference) on an oscilloscope, and they still deny it, then it's now come to the point of justifying a mistake, (maybe many mistakes.) They put the band on the capacitors, and marked the outside foil for a reason. Some companies even went as far to say "ground end" on the paper and foil wax capacitors. *It's there for a reason in point to point wiring type circuits.* Thanks for your kind comment!
Regarding a part with oxidized contacts, if you can remove the part, take it to a sink, rinse it in warm water then add barkeepers friend and some gentle scrubbing with a soft toothbrush. I have used this for awhile on old Betamax leaf switches and VHS mode switches and it works great.
Mr Carlson sir very nice arrange ment on your table every repairer and diy projects maker watch your video and thanks for for sharing this unit details.
A few small tips literally... Instead of using the cotton swabs with the large tips go to a women's beauty supply store or department. They have small tip swabs used for applying makeup. I found these are easier to get into tight wafer switches. Also, I use pieces of incontinence pads to absorb dripping contact cleaner or lubricant. Paper towels was not getting it done as well as these were.
In the future, maybe you can hook up a speaker to the amp that is motor-boating so we could hear (or witness) that sound and know what it is, should we hear it again at some point. 😉
If you ever hear it, you'll know it. It's a pretty unmistakable sound. As the name implies, it truly sounds like an old two-stroke outboard motor putting along.
Your video quality is excellent, just like everything you do being a great teacher for all of us. The only shortfall, as seen in this video, that I see is your audio. It appears you have one microphone which, in this video, is pointed in the direction of the Heathkit device. Assuming you have two audio inputs on your camera I would like to offer a gift of a set of Rode wireless Go microphones. This is the original version of one transmitter which clips to you shirt and one receiver that plugs into the other audio input of your camera. I have since purchased the newer version so I do not use these and giving them to you will be a great re-purposing. Please let me know if you would like these. They are a great tool. Thanks again for your superb videos!
Paul, good luck to you and yours on all fronts. Remember to have some young people who know about the lab around to help out. Never be the ONLY person who knows what you know. Look around and think what you would think if things were loused up and you were not there to help out.
Tarnish remover, what we used to have to do before that stuff came out. Well, I used to disassemble the waffer switch and use a pencile erraser to remove the tarnish.
Paul you were super, glad you had an issue and went thru TR the problems. Top Notch Job. Again you're the best bare none on You tube. Can't wait for more. 73s wb7qxu
The time taken to explain and test a noisy resistor suggests to me just change all the resistors as well as most of the capacitors. Those that are not noisy now probably will be in a couple of years! I used to change just the noisy resistors and the leaky caps but found it was just delaying the subtle faults for a while.
I am am in awe of some of your restorations, some of these radios look so good. I have been wondering if it is possible to take an old valve radio and carefully rebuild it from the chassis and improve the sound. I know it is not practical, but how intersting if the old schematics can be used with some new and possibly improved parts for a good sound and connection to DAB and regular record player. I can't find anyone who has tried yet.
Some digital multimeters actually have little light indicators on the ports themselves to indicate which jacks to use for each mode that utilizes the jacks. Mine that I have is one of those, altho mine is technically one of the harbor freight special type of digital multimeters. but it's not a bad quality. I'm just missing the thermal probe that went with it because my dad got it from a pawn shop i believe.
Hello Paul I read about cadmium coated chassis. Before I knew anything about it I didn't know what all that yellow dust was and I didn't know how dangerous it is when it turns to powder. I know I probably breathed some of that in. Its carcigenic and I'm sure you already know that. I now use a spray bottle of water and dampen it before wiping it out. I wish they didn't use cadmium way back then. I wonder if its outlawed today by EPA
It may have been worthwhile to briefly explain why a bias voltage is necessary when listening to the resistor. It's a very basic topic, but I think it's mildly interesting. However, Mr Carlson has probably explained it several times in other videos.
Good to see the progress and great result. Fortunate that you have spares...but if you didn't, would it be possible to repair the transformer or just not practical/economic?
I worked on an old Stromberg Carlson radio that had two 6V6 output tubes and when I finished, it was playing good but after playing awhile I noticed a drop in volume and one of the output tubes had a glowing screen grid. The output transformer had one side open. From now on I don't trust old push pull output transformers and if they're still working I rewire the tubes from power pentrode to triode mode unless I replace the old transformer with a reliable new one it will protect the output tubes. In triode mode the screen grid is wired directly to plate instead of the power supply through a screen resistor. This way the screen also looses voltage in case the transformer goes open
I think this is the first time I've heard Mr. Carlson mention noisy resistors or checking for them during a restoration. Are noisy resistors still a problem in modern day gear? How would you test resistors for noise without that old piece of Heathkit test gear?
the heath kit test set reminds me of the old sprague capacitor checker from years ago it was the best cap tester l ever used ,,you could check dielectric break down under load.
That resistor under the switch you were cleaning looks rather toasty where the lead goes into it. if you review the camera footage you had some bright light on there. you can see it really well
There is always a tradeoff between restoration and redesign. I have no answer what is correct. Would it make us happy seing the Sphinx with a repared nose or Nofretete with new eye. - a ridge walk!
It's all about balance. The mods done are to accommodate future service while using modern replacement components, (aside from the carbon comp resistors.) This won't be a shelf queen, so I want it to perform well in daily use. The components used won't change the way it performs drastically, but the mods will give it lower hum, and the audio transformer would give it "fuller audio."
@@MrCarlsonsLab I respect and understand you and your motivation to do everything as perfect as possible. One can bring a Ford T model close to the original (called restoration) or making a Hot Rod of the chassis. Both results are nice but serve another goal.
I never new about noisy resistors thanks.you do such a fantastic job u have been educated well. Could u please do some maintenance on modern ham gear like Icom particular ic with microprocessors in the circuits. Go over the schematic and then the circuits components. This would help a lot. De wb8idy in Swansboro nc usa
Really nice work. But speaking of grounding, it looks like several chassis grounds are made to the can capacitor lugs, which are grounded via mounting plates riveted to the chassis. Rather than trust the riveted connections, I would solder the plates to the chassis.
Hi Mr Carlson Will you be rewinding that audio output transformer, as per Dave Tipton, or is it not worth the while? Always look forward to your videos. Thanks for sharing the knowledge.
I have a vacuum tube headphone amp that is produced by one of your Canadian source ... Mapletree Audio Design. It has developed an intermittent noise that sounds like that resistor you found that was noisy. I was thinking of taking a scope to it to see if I could isolate there the noise was coming from. Thanks so much for such in-depth insight into electronics Sir! 73 - KF6IF
Hi Paul. Did i miss something or had you already matched the o/p valves on a valve tester before installing them, as i thought, with a push-pull design, it was good practice to do so per channel. If not, wouldn't their be problems with output from the amp. Ie an imbalance between the +ve & -ve parts of the o/p signal. Btw great videos, been subbed for ages, very informative. 👍
I had a 8 watt vacuum tube amp (stated) per channel push pull that was not much quieter that my 80watt per channel Denon amp. Where are these metrics added up? That said, the mains transformer in the vacuum tube amp was the same size as what was in the Denon amp (PMA 500) Both were relatively heavy amps.
Hi Paul I have enjoyed watching this series. Very detailed work. I have a question, the output power seems a bit low to me for 6v6’s running near 300v which should according to the data sheet should easily make 10watts even 14w. And the clipping appears substantially unequal. I would swap the 6v6s around and and see if the early clipping changes to the negative side of the waveform. Did you replace the phase inverter? The original tube may not be able to swing symmetrically.
I head nossink; bad old ears. What kind of noise is resistor noise? Changes in the voltage drop? You're using terms we noobs don't fully understand. I highly recommend micro fiber swabs, both flat and pointed. No little threads.
Hi Paul, Wondering why wood bases are bad practice for tube amplifiers? (Thinking specifically of Bottlehead products where components are mounted to an Aluminum top plate then supported by a wood base) Thank you for the video!
Hot components around wood, or just components in general around a wood frame is bad design practice. Resistors burn up, transformers short, capacitors pop, ETC. Unless the entire wooden structure is shielded, or there is some fire proof material used as a liner, I wouldn't want to leave the room with the device plugged in.... Even when it's off. You will notice the flame proof coating even in this old radio, (yellow color.)
I understand the colour code of the old plate resistor; yellow-mauve-yellow-silver meaning 470k 10%. I don't understand the colour code of the replacement with the extra red ring. If it stopped there it might mean 2%, but the silver ring is there as well. Pink could mean high stability, but it doesn't look like that. If it's worth keeping most of the heater current away from the pre-amp stage, why not go further and twist the wires? When you wound up the gain, the amplifier started clipping on the positive peaks before the negative peaks. Does that suggest non-optimum bias around the phase splitter?
Hi Paul, I was just wondering about the audio power of 6 watts you mentioned, I got the feeling from what you said 6 watts into 8 ohm would sound really loud? I'm just a bit confused, because modern solid-state amplifiers putting 6 watts into 8 ohms isn't really that loud. Is 6 watts into 8 ohms from a valve amplifier louder some how?
Hi Jason. 6 "Real" Watts into an 8 Ohm speaker is very loud. It's hard to explain if you are trying to give someone a loudness reference.... An AA5 radio with a class A output stage makes around 1 to 1.5 Watts, (depending on the output tube.) Have you ever turned an AA5's volume to the max? At 1 Watt, they are very loud. Most computer speakers (external desktop types) usually make 2 Watts or so.
@@MrCarlsonsLab thank you for your answer , I remember my grandfather and father for that matter taking about "real" watts from valve amplifier and talking them up compared to modern amps. I'm not quite old enough to have grown up with valve amps so don't have a frame of reference. Thanks once again
The speaker is another variable. Older speakers were designed for high efficiency and so they put out a lot of noise of six watts. The trade off was that they were not always as accurate as modern speakers. In todays world watts are very inexpensive and speakers are optimized for accuracy over efficiency. They waste more power, however they have a wider frequency response and lower distortion. Six watts into most modern speakers will be somewhat loud. Six watts into valve era speakers will be very very loud.
is there an another way to measure the resistor noise? I assume this is largely a carbon composition resistor problem as it can have raised inductance due to uneven conductance because of heating over time. this should not be a problem with metal film or oxide film type resistors?. or do other type of resistors suffer from it. quite possibly measuring the inductance and capacitance could be a good indicator?
Hi Greg. The 6V6 was cold (only heater warm,) this indicates the lack of plate voltage, plate voltage comes through the audio transformer. The only logical assumption would be an open winding.
PAUL'''''''ive got a question,,,, im going to order a multi capacitor kit,,,, in your mind what is the best brand out there''''''''i want the best' precision long lasting caps''''hope all is well'''''''73's james, oklahoma.
Did I understand you correctly that the chassis is cadmium coated? If so, why? You might have kept me from poisoning myself some day because I totally would have done something stupid in cleaning it. Maybe sand it and snort the dust to see what it smells like or licked it because I'm very weird.
The cadmium was plated onto the metal to prevent corrosion. Its a very effective treatment; however over a long period of time it degrades in a manner that presumably was not anticipated way back then . It is still used in military and naval applications due to its high resistance to salt and heat.
Very interesting. I never new that. I’ve been in the field since the 60’s. Where do you live? I used to live in Caledon East at Albion hills farm school in the 70’s. Got deported for stealing shepherd jobs from Canadians! I know so many were looking to tend sheep.
shocking!!!!!!!! i have a 1968 Zenith console in excellent condition for it's age has 8-track player, turntable and sam's schematic solid state. if your interested in this let me send you photo's.
![A Restoration Adventure - [ GE Radio Receiver Restoration Series ]](http://i.ytimg.com/vi/5y0RqivTy4Q/mqdefault.jpg)
![A Restoration Adventure - [ GE Radio Receiver Restoration Series ]](/img/tr.png)
![1940's Forestry Radio Receiver And Transmitter [Teardown With Circuit Description]](http://i.ytimg.com/vi/H7RKEDPUy-8/mqdefault.jpg)
To learn electronics in a very different and effective way, and gain access to Mr Carlson's personal designs and inventions, visit the Mr Carlson's Lab Patreon page here: www.patreon.com/MrCarlsonsLab
10 minutes explaining how to clean a switch is a good indicator how serious you take these things. And it seems you love you work/hobby. Great! Thanks for all your videos.
Glad you enjoyed it!
@@TD75 lol
And still the wonder grows, how one small head holds all he knows. The absolute best electronics repair channel on TH-cam.
Happy patron here. Really learning a lot. Thanks!
Thanks for your kind feedback Dave!
Glad I voted for restoring this receiver. I'm learning a lot plus it's interesting to see the effort the design engineers put into this product. It's definitely not a throw away consumer item.
The two things that made me happiest about this video: 1.} Your bench was a little bit messy from doing all the work. 2.} You got all the way to the end and found out you had a bad output transformer. You are human after all. Ha. That exact thing happened to me on a Grunow Teledial radio. The only difference was I didn't have one just laying around. I had to buy a speaker with one mounted to it and switch it over. Thanks for the series. Loving it.
I like you use old devices to check the values. The display of the HP ohmmeter is super cool, the numbers are nice and round 👌
You know it's an interesting video, when you watch with such interest that your coffee goes cold. Cheers from Winnipeg.
Thanks a lot! I love this series. You've managed to bring back "the good old days" feeling of your old videos with the new lab and updated equipment and other improvements. I love having the HP nixie tube meter and the vfd display in the Agilent meter in the shot at the same time. (in case you can't decide which you like better, you're covered!)
You really have a way of talking that makes me never get bored of it even though most of your videos aren't short and I don't understand half of what you're doing 😄 And what really intrigues me is how you can work in a place that is always clean and tidy, I don't do a quarter of what you do and I work in a place like a war zone 😂
You explain everything so well Paul. Thanks for the electronics learning experience I can't find anywhere else on YT.
Looking forward for part 4.
Why did the capacitor kiss the diode?
He couldn’t resistor 😊
Learning a lot here. Thanks, Paul.
My pleasure!
And that's just the amplifier! Looking forward to the radio portion. Thanks for the plate wiring "gotcha;" I'm sure that'll bite me at some point. 😁👍️
Thank you Paul! I look forward to part 4.
You are very welcome!
Today I learned that resistors can be noisy... I wish I had room in my life for another expensive hobby, I'd be diving right in buying equipment and supplies... and Mr. Carlson's training materials! I'll have to satisfy myself with the occasional video, alas, but I'm very happy to know that there's people out there keeping all this old gear working and living on into the 21st Century.
Am presently working on a 60 year old admiral small console record player that uses a 12ax7 and two 50c5 tubes in a push pull arrangement. 4N2A amplifier. Every time I think I'm close to finished I watch one of your videos start checking the numerous other things. you talk about. I don't want to do any damage to the unit by playing too much.
It sounds like a series type setup. If it doesn't have a power transformer, be careful! You may want to look into an isolation transformer.
Excellent jwl! I hope your project goes well!
Mr Carlson your shortwave Reciver restoration is so awesome
Love the Content and the 4K is amazing
Ahh, so therapeutic! Thank you very much.
Glad you enjoyed it!
Superb tutorial as ever!
I learnt a lot. Thanks.
I wasn't previously aware of diode valve limitations "soft rectifiers" etc.
- I wonder if ElectroBoom knows....
Looking forward to the next installment!
My office is across the street from the old Heathkit/Zenith plant! So cool!
Putting the transformer shield to circuit 0V is a nice tip, too.
9:10 "...10 minutes later, it's doing the same thing and Ahhh! I got to pull the whole thing apart again" - > Story of my life.
Great video as always! Would love to see a frequency response analysis of the amplifier, and some data on how the tone knob changes that.
I think one of the more important points that you made in this video is lubricating the shafts of potentiometers, and rotary switches,, I have spent many hours freeing up stuck shafts on those devices,,, :-)
This was awesome! Just finished watching this one today. I am definitely going to go over it again with a note book as you suggested. There is so much wisdom in how you so things. Thanks for an awesome video.
There isn't anyone who is as thorough as YOU!
I'm very interested in the identification of which lead is connected to capacitor's "outter foil." Others seem very uninterested in this critical noise reduction technique. Why? It isn't that difficult to implement!
ALSO was 'educated' myself about noisy resistors. That could be maddening! Didn't know about that test? Would noise appearbon scope of a powered up unit but with no input?
The answer is very simple Tom. The reason they deny it is: They have been doing it wrong for years, then they find it hard to admit and come too terms with that. If you can see an electrical difference (a very pronounced difference) on an oscilloscope, and they still deny it, then it's now come to the point of justifying a mistake, (maybe many mistakes.) They put the band on the capacitors, and marked the outside foil for a reason. Some companies even went as far to say "ground end" on the paper and foil wax capacitors. *It's there for a reason in point to point wiring type circuits.* Thanks for your kind comment!
Regarding a part with oxidized contacts, if you can remove the part, take it to a sink, rinse it in warm water then add barkeepers friend and some gentle scrubbing with a soft toothbrush. I have used this for awhile on old Betamax leaf switches and VHS mode switches and it works great.
Oregon USA here, the backyard of Tektronix.
A few days ago I bought my first oscilloscope ... it's a 465 model. I am very happy about that.
@@thomass7877 Ah yes! Nice old Tek item.
Mr Carlson sir very nice arrange ment on your table every repairer and diy projects maker watch your video and thanks for for sharing this unit details.
You are very welcome!
I am really enjoying this series. I'll be looking forward to watching part 4.
Another great video, thanks Paul. Wish I’d known the trick about clipping the “ears” long ago. Would have saved me a lot of bent terminals
You're very welcome!
Freeze spraying resistors can reveal them by either making them noisier or quieter. A fairly quick method for finding them.
A few small tips literally... Instead of using the cotton swabs with the large tips go to a women's beauty supply store or department. They have small tip swabs used for applying makeup. I found these are easier to get into tight wafer switches. Also, I use pieces of incontinence pads to absorb dripping contact cleaner or lubricant. Paper towels was not getting it done as well as these were.
That's a good idea. Also, with foam swabs you don't run the risk of getting cotton fibers caught in the switch contacts.
Well done Paul. Appreciate your skill. Thanx Ken from gpt ms
In the future, maybe you can hook up a speaker to the amp that is motor-boating so we could hear (or witness) that sound and know what it is, should we hear it again at some point. 😉
If you ever hear it, you'll know it. It's a pretty unmistakable sound. As the name implies, it truly sounds like an old two-stroke outboard motor putting along.
Mr Carlson you are good at electronics restoration
That was so interesting. The anticipation is building 😊
Glad you're enjoying Pauline!
Your video quality is excellent, just like everything you do being a great teacher for all of us. The only shortfall, as seen in this video, that I see is your audio. It appears you have one microphone which, in this video, is pointed in the direction of the Heathkit device. Assuming you have two audio inputs on your camera I would like to offer a gift of a set of Rode wireless Go microphones. This is the original version of one transmitter which clips to you shirt and one receiver that plugs into the other audio input of your camera. I have since purchased the newer version so I do not use these and giving them to you will be a great re-purposing. Please let me know if you would like these. They are a great tool. Thanks again for your superb videos!
Paul, good luck to you and yours on all fronts. Remember to have some young people who know about the lab around to help out. Never be the ONLY person who knows what you know. Look around and think what you would think if things were loused up and you were not there to help out.
Well thought out there Mr C. And more useful information for us to put in the tool box. Thanks !
You are very welcome!
Good teacher
another excellent video.. keep it coming
Thanks for that Doctor C. I got some good tips from this one again. (I say Doctor, because you must have a PhD in electrical engineering.)
Never new a resistor could be noisy 🤔
I have that exact screwdriver set. They are great for setting right there on the bench.
Tarnish remover, what we used to have to do before that stuff came out. Well, I used to disassemble the waffer switch and use a pencile erraser to remove the tarnish.
Thank you!!
You're welcome!
mr. Carlson's lab? More like mr. Carlson's rad
really great - thanks Paul...
You're welcome David!
Paul you were super, glad you had an issue and went thru TR the problems. Top Notch Job. Again you're the best bare none on You tube. Can't wait for more. 73s wb7qxu
Thanks for your kind comment Mike!
The time taken to explain and test a noisy resistor suggests to me just change all the resistors as well as most of the capacitors. Those that are not noisy now probably will be in a couple of years! I used to change just the noisy resistors and the leaky caps but found it was just delaying the subtle faults for a while.
Finally!! TH-cam mobile is allowing greater than 480p resolution! The first two parts of this series has been limited and a pixelly mess on mobile.
I am am in awe of some of your restorations, some of these radios look so good. I have been wondering if it is possible to take an old valve radio and carefully rebuild it from the chassis and improve the sound. I know it is not practical, but how intersting if the old schematics can be used with some new and possibly improved parts for a good sound and connection to DAB and regular record player. I can't find anyone who has tried yet.
I love your lab and would be more than happy to be your assistant. Are you hiring? 😘😘😘
Some digital multimeters actually have little light indicators on the ports themselves to indicate which jacks to use for each mode that utilizes the jacks. Mine that I have is one of those, altho mine is technically one of the harbor freight special type of digital multimeters. but it's not a bad quality. I'm just missing the thermal probe that went with it because my dad got it from a pawn shop i believe.
What a great idea! Indicators reminding you of which terminals to use! A++!
Is Part 4 already available...? I'm eagerly waiting for it 🙏
Here you go, enjoy: th-cam.com/video/g3CUQaQ-_gM/w-d-xo.html
Hello Paul I read about cadmium coated chassis. Before I knew anything about it I didn't know what all that yellow dust was and I didn't know how dangerous it is when it turns to powder. I know I probably breathed some of that in. Its carcigenic and I'm sure you already know that. I now use a spray bottle of water and dampen it before wiping it out. I wish they didn't use cadmium way back then. I wonder if its outlawed today by EPA
It's banned by RoHS.
It may have been worthwhile to briefly explain why a bias voltage is necessary when listening to the resistor. It's a very basic topic, but I think it's mildly interesting. However, Mr Carlson has probably explained it several times in other videos.
Now I need to adapt one of my low noise high voltage power supplies to an AC coupled amplifier...
Good to see the progress and great result. Fortunate that you have spares...but if you didn't, would it be possible to repair the transformer or just not practical/economic?
I worked on an old Stromberg Carlson radio that had two 6V6 output tubes and when I finished, it was playing good but after playing awhile I noticed a drop in volume and one of the output tubes had a glowing screen grid. The output transformer had one side open. From now on I don't trust old push pull output transformers and if they're still working I rewire the tubes from power pentrode to triode mode unless I replace the old transformer with a reliable new one it will protect the output tubes. In triode mode the screen grid is wired directly to plate instead of the power supply through a screen resistor. This way the screen also looses voltage in case the transformer goes open
I think this is the first time I've heard Mr. Carlson mention noisy resistors or checking for them during a restoration. Are noisy resistors still a problem in modern day gear? How would you test resistors for noise without that old piece of Heathkit test gear?
the heath kit test set reminds me of the old sprague capacitor checker from years ago it was the best cap tester l ever used ,,you could check dielectric break down under load.
That resistor under the switch you were cleaning looks rather toasty where the lead goes into it. if you review the camera footage you had some bright light on there. you can see it really well
There is always a tradeoff between restoration and redesign. I have no answer what is correct. Would it make us happy seing the Sphinx with a repared nose or Nofretete with new eye. - a ridge walk!
It's all about balance. The mods done are to accommodate future service while using modern replacement components, (aside from the carbon comp resistors.) This won't be a shelf queen, so I want it to perform well in daily use. The components used won't change the way it performs drastically, but the mods will give it lower hum, and the audio transformer would give it "fuller audio."
@@MrCarlsonsLab I respect and understand you and your motivation to do everything as perfect as possible.
One can bring a Ford T model close to the original (called restoration) or making a Hot Rod of the chassis.
Both results are nice but serve another goal.
It was exciting again. Seen on 30-5-22 at 16:30 in the NL. pe1krx.
I personally do not see anything wrong with a bit of "motorboating".
How much better would it be if you used screened cables everywhere please?
Do you have a list of different chemicals you use? Your go to cleaners, lubricants, fluxes, etc?
I never new about noisy resistors thanks.you do such a fantastic job u have been educated well. Could u please do some maintenance on modern ham gear like Icom particular ic with microprocessors in the circuits. Go over the schematic and then the circuits components. This would help a lot. De wb8idy in Swansboro nc usa
Really nice work. But speaking of grounding, it looks like several chassis grounds are made to the can capacitor lugs, which are grounded via mounting plates riveted to the chassis. Rather than trust the riveted connections, I would solder the plates to the chassis.
Do metal film resistors generate less noise than carbon comp?
Typically yes.
Part 4? 😎
Hi Mr Carlson
Will you be rewinding that audio output transformer, as per Dave Tipton, or is it not worth the while?
Always look forward to your videos. Thanks for sharing the knowledge.
Hi Daniel. No, I have mounted the new transformer, so no point.
could you please tell also where do you get (buy ) your tubes , resistor , capacitor
I have a vacuum tube headphone amp that is produced by one of your Canadian source ... Mapletree Audio Design. It has developed an intermittent noise that sounds like that resistor you found that was noisy. I was thinking of taking a scope to it to see if I could isolate there the noise was coming from. Thanks so much for such in-depth insight into electronics Sir! 73 - KF6IF
Hi from Kurnool Andhra Pradesh India
Very bad that Heathkit didn't place a warning near the 'AUDIO' jack that it can output over 200 volts in the 'NOISE" mode ! ;)
Hi Paul. Did i miss something or had you already matched the o/p valves on a valve tester before installing them, as i thought, with a push-pull design, it was good practice to do so per channel. If not, wouldn't their be problems with output from the amp. Ie an imbalance between the +ve & -ve parts of the o/p signal.
Btw great videos, been subbed for ages, very informative. 👍
I had a 8 watt vacuum tube amp (stated) per channel push pull that was not much quieter that my 80watt per channel Denon amp.
Where are these metrics added up?
That said, the mains transformer in the vacuum tube amp was the same size as what was in the Denon amp (PMA 500)
Both were relatively heavy amps.
Hi Paul I have enjoyed watching this series. Very detailed work.
I have a question, the output power seems a bit low to me for 6v6’s running near 300v which should according to the data sheet should easily make 10watts even 14w. And the clipping appears substantially unequal. I would swap the 6v6s around and and see if the early clipping changes to the negative side of the waveform. Did you replace the phase inverter? The original tube may not be able to swing symmetrically.
How do you clean the bottom side of the switch disc (wafer), which is not so easily accessible as the top side?
When a switch is "stamped together" like this one, you have to rely on contact cleaner and switch movement for the hidden side.
@@MrCarlsonsLab Ah - OK! thought so. I tried to use stiff paper and folded it until it was thick enough to be squeezed under the wafer.
I head nossink; bad old ears. What kind of noise is resistor noise? Changes in the voltage drop? You're using terms we noobs don't fully understand.
I highly recommend micro fiber swabs, both flat and pointed. No little threads.
Hi Paul, Wondering why wood bases are bad practice for tube amplifiers? (Thinking specifically of Bottlehead products where components are mounted to an Aluminum top plate then supported by a wood base) Thank you for the video!
Hot components around wood, or just components in general around a wood frame is bad design practice. Resistors burn up, transformers short, capacitors pop, ETC. Unless the entire wooden structure is shielded, or there is some fire proof material used as a liner, I wouldn't want to leave the room with the device plugged in.... Even when it's off. You will notice the flame proof coating even in this old radio, (yellow color.)
@@MrCarlsonsLab Super Thanks for the explanation!....will be sure to fire proof shield my Bottlehead amp
I understand the colour code of the old plate resistor; yellow-mauve-yellow-silver meaning 470k 10%. I don't understand the colour code of the replacement with the extra red ring. If it stopped there it might mean 2%, but the silver ring is there as well. Pink could mean high stability, but it doesn't look like that.
If it's worth keeping most of the heater current away from the pre-amp stage, why not go further and twist the wires?
When you wound up the gain, the amplifier started clipping on the positive peaks before the negative peaks. Does that suggest non-optimum bias around the phase splitter?
Hi Paul, I was just wondering about the audio power of 6 watts you mentioned, I got the feeling from what you said 6 watts into 8 ohm would sound really loud? I'm just a bit confused, because modern solid-state amplifiers putting 6 watts into 8 ohms isn't really that loud. Is 6 watts into 8 ohms from a valve amplifier louder some how?
Hi Jason. 6 "Real" Watts into an 8 Ohm speaker is very loud. It's hard to explain if you are trying to give someone a loudness reference.... An AA5 radio with a class A output stage makes around 1 to 1.5 Watts, (depending on the output tube.) Have you ever turned an AA5's volume to the max? At 1 Watt, they are very loud. Most computer speakers (external desktop types) usually make 2 Watts or so.
@@MrCarlsonsLab thank you for your answer , I remember my grandfather and father for that matter taking about "real" watts from valve amplifier and talking them up compared to modern amps. I'm not quite old enough to have grown up with valve amps so don't have a frame of reference.
Thanks once again
The speaker is another variable. Older speakers were designed for high efficiency and so they put out a lot of noise of six watts. The trade off was that they were not always as accurate as modern speakers. In todays world watts are very inexpensive and speakers are optimized for accuracy over efficiency. They waste more power, however they have a wider frequency response and lower distortion. Six watts into most modern speakers will be somewhat loud. Six watts into valve era speakers will be very very loud.
layout management. that answers my question why philco 112 chassis wires look nothing like the diagram
is there an another way to measure the resistor noise? I assume this is largely a carbon composition resistor problem as it can have raised inductance due to uneven conductance because of heating over time. this should not be a problem with metal film or oxide film type resistors?. or do other type of resistors suffer from it. quite possibly measuring the inductance and capacitance could be a good indicator?
Hi, Paul. It would be nice if you teach us how to make a resistor noise sniffer. Could be a good patreon project 😉
It is already there.
th-cam.com/video/uVkJqqZroN0/w-d-xo.html
@@csabahollo6922 Really?... can't find it
Paul i guess what that street noise may be hard work of worldwide logistic routine,
because eastern Europe had mass invasion of locust in this year.
Mr Carlson how do you know if the transformer
Hi Greg. The 6V6 was cold (only heater warm,) this indicates the lack of plate voltage, plate voltage comes through the audio transformer. The only logical assumption would be an open winding.
PAUL'''''''ive got a question,,,, im going to order a multi capacitor kit,,,, in your mind what is the best brand out there''''''''i want the best' precision long lasting caps''''hope all is well'''''''73's james, oklahoma.
Did I understand you correctly that the chassis is cadmium coated? If so, why? You might have kept me from poisoning myself some day because I totally would have done something stupid in cleaning it. Maybe sand it and snort the dust to see what it smells like or licked it because I'm very weird.
The cadmium was plated onto the metal to prevent corrosion. Its a very effective treatment; however over a long period of time it degrades in a manner that presumably was not anticipated way back then . It is still used in military and naval applications due to its high resistance to salt and heat.
Very interesting. I never new that. I’ve been in the field since the 60’s. Where do you live? I used to live in Caledon East at Albion hills farm school in the 70’s. Got deported for stealing shepherd jobs from Canadians! I know so many were looking to tend sheep.
Mr Carlson my hobbys are painting pictures and lisining to shortwave and ssb iam thinking about getting my ham license I have 4 shortwave receivers
😎👍
shocking!!!!!!!! i have a 1968 Zenith console in excellent condition for it's age has 8-track player, turntable and sam's schematic solid state. if your interested in this let me send you photo's.
do i dare?? BETTER THAN NEW????