Yes, and I'm more than grateful that he takes time to do this. Even if I'm no electrical engineer, this is so interesting to know and helpful when using my tube gears. Thank you so much!
Hi Mark, I'm a 67 year old novice to this hobby with a lot more enthusiasm then knowledge, this video has just helped me a great deal. You are a excellent teacher. Thank you for sharing your knowledge.
I can’t get over how beautiful and simple the layout of that amp is. Tube gear is truly timeless. Thanks for another great vid, and I’m so happy to see how well your health seems to be doing too.
You can build one exactly like it with modern FETs. Exactly the same schematic, just lower supply voltage and resistor values. Tubes and FETs are functionally the same.
Hi Mark. Just wish to thank you very much for you time and effort in creating the blue glow channel videos. I’ve recently joined the hobby of electronics and attempting the repair of my own vintage Australian radio/stereograms. Your tutorials are interesting, immensely helpful and gives confidence in attempting the repairs. Your efforts are really appreciated. Kind Regards. Craig
Great job at reminding folks to use the tool between your ears! Your triage approach is what I find works the best over time. You accumulate knowledge quickly and can prevent complicating the problems with a mistake by shotgunning. Its easy to get tempted but not recommended for gear you don't have prior experience on. Keep em glowing!
Very informative video! Thanks so much for taking the time to make this. As others have commented, seems there are lots of videos showing repairs on tube amps, but not many videos talking about and showing the troubleshooting process. Love to see more videos like this on TH-cam.
Hi, great video. For those that think these bat eared Hi Fi reviewers who claim they can hear the difference between a carbon resistor and a metal film, or a £1 cap vs £10 cap is utter bollocks. Once you hit 30, if you can hear above 15kHz you are doing very well. It's all about which magazine they work for, and how much they are being paid by the manufacturer. If that amp was mine I would be replacing or reforming all those old caps on sight. Some of those carbon resitors can double in value over the years.
Mains voltage in the U.K. (and EU) is 230V +/- 7%, and all equipment has to be designed to cope with this. I'd be surprised if it was diffent in the US when these were designed. I wouldn't expect to see precise measurements as per schematics anywhere. (When Iwas taught to fault find electronics, I was taught to measure the signal in the middle of the circuit first. That way you confirm that half the circuit is either good or bad without having to go through each step: very efficient way to fault find.
When doing multi part series, always, always put a link in the description for your previous posts! Your subscription base will stick to you like glue and I guarantee your new followers will be looking for the previous not yet seen.
@@Blueglow, thanks... I need to learn how to find TH-cam series posts. I'm searching using TH-cam title such as and example "Finding the Failing Component" in an attempt to locate other episodes.
hi, love your videos. in this you gave an example of someone wanting to keep the old bumblebee coplingscaps, and you said yes they give the original sound, even if they are leaky, but this is not completely correct. they DID give the amp its original sound when they were new, and they actually functioned as they were ment to, but now when they are leaky and functions more as resistors, they give a completely different sound then they did as new. but your point with that example is absolutely correct.
Lovely run-down on sensible troubleshooting! I saw another vid where, to keep your amp looking nice and authentic, the guy was encasing the new coupling caps in the old wax and paper housing, by slitting old cap sideways and using the coverings. Looked good.
For whatever it is worth: Carbon composition resistors often came with silver band tolerance, meaning 10%. Carbon film resistors typically are 5% (gold band) tolerance. Metal film resistor are mostly with brown tolerance band, meaning 1%. Sometimes you find red band, meaning 2%. And then there are metal oxide resistors that may again be 5% tolerance, because their temperature range is higher. But all these film resistors have one thing in common, compared to the composition type. Their resistance element is on the outside of the ceramic core and has been trimmed to the desired value by cutting a spiral to the film. The trimming allows a tight resistance tolerance that is not possible with composite type resistors. Also, the location of the resistive element on the outside improves power handling and reduces the temperature caused variation of the resistance. That also contributes to a tighter tolerance specification. But is there any negative effect on these film structures? Of course. First, there is a little inductance caused by the spiral cut. Second, the maximum voltage is limited by the narrow gaps from turn to turn of the spiral cut. You typically did not see a fixed specification for maximum voltage on the composition type resistors, while all the film resistors include that specification. I have witnessed a few cases of spark-over on film resistors in situation where the applied power was well within nominal specification, but the momentary voltage was too high.
Awesome Mark! Going to put this information to use this afternoon. I have a AA5 radio with no output/sound. Going to use the schematic and my dmm to troubleshoot.
Great job! Yes, first, visual inspection. Then (I) check for shorts in the obvious places. Then bring up on variac and/or dim bulb if indicated. Then it's off to the races measuring voltages etc!
Truly a great tutorial! Thank you so much. I’m learning a lot from your videos. Although it’s a bit pity that you found the issue so quick. I would have liked to see you go further. I’m troubleshooting a cheap Chinese diy build tube amp myself. As a step up to eventually build one myself. Can’t seem to find the failure yet, however. I do believe it’s somewhere in the signal path but I don’t really know how to start looking. Guess I’m shot gunning at the moment 😅.
Mark great video, it has been 40 years since I have heard someone explain coupling capacitors, Mst Wlliams my electronics instructor at Redstone Arsenal.
You should ALWAYS find the original problem first. If for no other reason, the possibility that you made a mistake in your rebuild and introduced a second trouble.
That being said, if a (tube) set has paper/wax caps, they’re outta there! The last thing I want to do is burn up a rare or hard-to-find tube because of a bad bypass or coupling cap. Plus, if it does fix the problem, then I’m not overly concerned about which cap may have been bad, and if it doesn’t, then - at least - it reduces the number of problem points to check. And that saves time (and money, if you’re doing repair as a business)! Also, I always replace any across-the-line caps with -x/-y rated safety caps, just as a matter of routine - no point having to clean out blown up capacitor innards out of the set if I don’t have to! 😎
Would you not want to power the unit up on the variac/dim bulb after replacing the faulty rectifier tube? Only after the tube replacement is the rest of the circuit getting voltage (other than filament) for the first time. Just curious.
That's considered the most reliable standard in multimeters! I got my 87-5 from a friend who found it in the middle of the road. I gave him $200 for it! Look at Dave's channel on testing meters (EEV Blog).
Amazing - so you can actually clip your - voltmeter probe to ground and poke around with your + probe pretty much anywhere as long as your voltmeter can take more than max voltage of the circuit in AC or DC ?
Hey Mark. Another great video. How can I learn more about which old console amplifiers are worth restoring and which are junk. Are their specific old radio & tv consoles that you keep on your radar? Specific manufacturers, specific time periods? Thanks.
Hi, I have a Marshall JVM 205C Witch is making a loud whistle when I raes the volume Nobody as been working on it or opened it up I have changed the tubes but still the same whistle realy loud Do you have any tips what to look at Nothing as been changed on the amp it has been put aside for a while and when I started it up the whistle was there It’s a + 1khz tone Thank you I’m sure if anyone knows it’s you what can course this
I always agonize over what to do with a console amp after restoring /repairing it if I do not have the console to reinstall it in. What practical use is there for this thing now? The learning and practice experience gained from doing the work might be alone worth the effort but what would you do with it?
When an electrolytic cap is spilling electrolyte, I replace it before powering up the device... many times... OR sometimes I just power it up and see if it explodes.
true mark changing every part may not work. what happen if you put a part in the wrong spot the unit still will not work and you will still be trying to find a fault
I know it’s a personal sacrifice to do these videos but I certainly appreciate you doing it. Many thanks!
Yes, and I'm more than grateful that he takes time to do this. Even if I'm no electrical engineer, this is so interesting to know and helpful when using my tube gears. Thank you so much!
Hi Mark, I'm a 67 year old novice to this hobby with a lot more enthusiasm then knowledge, this video has just helped me a great deal. You are a excellent teacher. Thank you for sharing your knowledge.
I can’t get over how beautiful and simple the layout of that amp is. Tube gear is truly timeless.
Thanks for another great vid, and I’m so happy to see how well your health seems to be doing too.
Btw, what’s your handle on AK? I’ve been a subscriber for quite a while now. Best online audio forum IMO.
You can build one exactly like it with modern FETs. Exactly the same schematic, just lower supply voltage and resistor values. Tubes and FETs are functionally the same.
Hi Mark. Just wish to thank you very much for you time and effort in creating the blue glow channel videos. I’ve recently joined the hobby of electronics and attempting the repair of my own vintage Australian radio/stereograms. Your tutorials are interesting, immensely helpful and gives confidence in attempting the repairs. Your efforts are really appreciated. Kind Regards. Craig
Thank You Mark! I've learned more from the video than all the videos I've watched in the last 2 years.
Great job at reminding folks to use the tool between your ears! Your triage approach is what I find works the best over time. You accumulate knowledge quickly and can prevent complicating the problems with a mistake by shotgunning. Its easy to get tempted but not recommended for gear you don't have prior experience on. Keep em glowing!
Very informative video! Thanks so much for taking the time to make this. As others have commented, seems there are lots of videos showing repairs on tube amps, but not many videos talking about and showing the troubleshooting process. Love to see more videos like this on TH-cam.
Nice to see you putting out some videos again Mark, you look like you're doing well health-wise!.
Really helpful video for me. These are all individual pieces of info I knew beforehand, but this helps piece them together in a usable logical way
Hi, great video. For those that think these bat eared Hi Fi reviewers who claim they can hear the difference between a carbon resistor and a metal film, or a £1 cap vs £10 cap is utter bollocks. Once you hit 30, if you can hear above 15kHz you are doing very well. It's all about which magazine they work for, and how much they are being paid by the manufacturer.
If that amp was mine I would be replacing or reforming all those old caps on sight.
Some of those carbon resitors can double in value over the years.
Mains voltage in the U.K. (and EU) is 230V +/- 7%, and all equipment has to be designed to cope with this. I'd be surprised if it was diffent in the US when these were designed. I wouldn't expect to see precise measurements as per schematics anywhere.
(When Iwas taught to fault find electronics, I was taught to measure the signal in the middle of the circuit first. That way you confirm that half the circuit is either good or bad without having to go through each step: very efficient way to fault find.
When doing multi part series, always, always put a link in the description for your previous posts! Your subscription base will stick to you like glue and I guarantee your new followers will be looking for the previous not yet seen.
They are in a "series", but you have a good point.
@@Blueglow, thanks... I need to learn how to find TH-cam series posts. I'm searching using TH-cam title such as and example "Finding the Failing Component" in an attempt to locate other episodes.
Les Merryman just click on blue glow electronics and scroll through uploads, or videos or play lists, and you will find them.
Great video. Fundamentals of troubleshooting and good techniques are difficult to develop for beginners. Thanks for sharing your knowledge.
hi, love your videos. in this you gave an example of someone wanting to keep the old bumblebee coplingscaps, and you said yes they give the original sound, even if they are leaky, but this is not completely correct. they DID give the amp its original sound when they were new, and they actually functioned as they were ment to, but now when they are leaky and functions more as resistors, they give a completely different sound then they did as new. but your point with that example is absolutely correct.
Lovely run-down on sensible troubleshooting!
I saw another vid where, to keep your amp looking nice and authentic, the guy was encasing the new coupling caps in the old wax and paper housing, by slitting old cap sideways and using the coverings. Looked good.
For whatever it is worth: Carbon composition resistors often came with silver band tolerance, meaning 10%. Carbon film resistors typically are 5% (gold band) tolerance. Metal film resistor are mostly with brown tolerance band, meaning 1%. Sometimes you find red band, meaning 2%. And then there are metal oxide resistors that may again be 5% tolerance, because their temperature range is higher. But all these film resistors have one thing in common, compared to the composition type. Their resistance element is on the outside of the ceramic core and has been trimmed to the desired value by cutting a spiral to the film. The trimming allows a tight resistance tolerance that is not possible with composite type resistors. Also, the location of the resistive element on the outside improves power handling and reduces the temperature caused variation of the resistance. That also contributes to a tighter tolerance specification. But is there any negative effect on these film structures? Of course. First, there is a little inductance caused by the spiral cut. Second, the maximum voltage is limited by the narrow gaps from turn to turn of the spiral cut.
You typically did not see a fixed specification for maximum voltage on the composition type resistors, while all the film resistors include that specification. I have witnessed a few cases of spark-over on film resistors in situation where the applied power was well within nominal specification, but the momentary voltage was too high.
Great video Mark and good to see you get back into it. Cheers
This is a great series, this episode is especially helpful to me.
Great example and very and informative , thanks for showing how to properly diagnose a basic amp, More please !
Great video. After watching it’s all starting to make sense. Thank you.
Awesome Mark! Going to put this information to use this afternoon. I have a AA5 radio with no output/sound. Going to use the schematic and my dmm to troubleshoot.
Great job! Yes, first, visual inspection. Then (I) check for shorts in the obvious places. Then bring up on variac and/or dim bulb if indicated. Then it's off to the races measuring voltages etc!
Thank you Mark! Love your videos. They are so helpful. I hope I can keep learning with your help.
Truly a great tutorial! Thank you so much. I’m learning a lot from your videos. Although it’s a bit pity that you found the issue so quick. I would have liked to see you go further. I’m troubleshooting a cheap Chinese diy build tube amp myself. As a step up to eventually build one myself. Can’t seem to find the failure yet, however. I do believe it’s somewhere in the signal path but I don’t really know how to start looking. Guess I’m shot gunning at the moment 😅.
Those volt numbers on schematic were probably used with a 20k/volt meter of the time that gives you a different number than the DMM as well.
Mark great video, it has been 40 years since I have heard someone explain coupling capacitors, Mst Wlliams my electronics instructor at Redstone Arsenal.
Another awesome video! We all appreciate what you do and thank you for your time :)
First rate seat of pants basic repair trouble shoot of a nice simple unit.
Thanks.
You should ALWAYS find the original problem first. If for no other reason, the possibility that you made a mistake in your rebuild and introduced a second trouble.
Always nice to have a schematic with voltages marked!
Agree
Thank you Teacher. Very happy for what i'm learning
Excellent video Mark, thanks
Thanks for the lesson. I found it very useful.
Great class today...Thanks Mark
I don't think you'd get the original sound with leaky capacitors since they didn't leak and cause the tubes to distort the signal when they were new.
this is Gold, man. Gold, for a noob like me. thank you!
Great video! Very helpful!
Great video. Thanks!
That being said, if a (tube) set has paper/wax caps, they’re outta there! The last thing I want to do is burn up a rare or hard-to-find tube because of a bad bypass or coupling cap. Plus, if it does fix the problem, then I’m not overly concerned about which cap may have been bad, and if it doesn’t, then - at least - it reduces the number of problem points to check. And that saves time (and money, if you’re doing repair as a business)! Also, I always replace any across-the-line caps with -x/-y rated safety caps, just as a matter of routine - no point having to clean out blown up capacitor innards out of the set if I don’t have to! 😎
Would you not want to power the unit up on the variac/dim bulb after replacing the faulty rectifier tube? Only after the tube replacement is the rest of the circuit getting voltage (other than filament) for the first time. Just curious.
That's considered the most reliable standard in multimeters! I got my 87-5 from a friend who found it in the middle of the road. I gave him $200 for it! Look at Dave's channel on testing meters (EEV Blog).
Amazing - so you can actually clip your - voltmeter probe to ground and poke around with your + probe pretty much anywhere as long as your voltmeter can take more than max voltage of the circuit in AC or DC ?
Thanks for the video. The term short as used to power the rest of the circuit could be confusing to beginners, b/c short means something is wrong.
Thanks Mark!
Really cool stuff thanks
thank you so much great teacher!!!
Is there a way to fix the old wax and paper capacitors? They do give a vintage look to old radios and amps.
If you have the patience to do it, some people empty out the shell and mount the new capacitor inside and fill up with wax.
@@migsvensurfing6310 I've seen that in another video not too long ago.
Hey Mark. Another great video. How can I learn more about which old console amplifiers are worth restoring and which are junk. Are their specific old radio & tv consoles that you keep on your radar? Specific manufacturers, specific time periods? Thanks.
Hi,
I have a Marshall JVM 205C
Witch is making a loud whistle when I raes the volume
Nobody as been working on it or opened it up
I have changed the tubes but still the same whistle realy loud
Do you have any tips what to look at
Nothing as been changed on the amp it has been put aside for a while and when I started it up the whistle was there
It’s a + 1khz tone
Thank you
I’m sure if anyone knows it’s you what can course this
I always agonize over what to do with a console amp after restoring /repairing it if I do not have the console to reinstall it in. What practical use is there for this thing now? The learning and practice experience gained from doing the work might be alone worth the effort but what would you do with it?
Greg Clemen thanks for the suggestions. I admire your loyalty to “tube technology “
32:17 ... Yellow-violet-yellow is 470k ohms, not 470 ohms. 470 ohms would be yellow-violet-brown.
Indeed, was just me mis speaking.
Great stuff. Thanx.
When an electrolytic cap is spilling electrolyte, I replace it before powering up the device... many times... OR sometimes I just power it up and see if it explodes.
That's ridicules about leaving in an ol' cap!! The last person should have known better.
true mark changing every part may not work. what happen if you put a part in the wrong spot the unit still will not work and you will still be trying to find a fault
Good stuff......
Greetings:
R7 Yellow Violet Yellow is 470 K ohms not 470 ohms. Set your meter so you can read the range display, not just the numerals.
Thank you!!!!!
Don't own a capacitor tester, don't want one. If in doubt, change it out. Capacitors are cheaper than tubes.
Metal -film sound! LOL!
Yeah... A little metalic sound to it, LoL.