Thank you for this tip. I just replaced the filter caps in my 79 super. I used a MOD 500v 20uf in that position. It lasted about 2 seconds before the magic smoke came out. I am going to try replacing it with two of the 40uf 500v MODs next. Hope it works.
Thanks so much, this is a very timely video as I have a 80 ultra linear Super on my bench right now. This one has a non ultra linear unknown replacement OT in it, and I'm really struggling to get it to sound good. Someday, I hope to have at least a portion of your expertise in these matters, then I'd likely not be chasing my tail around getting nowhere. Cheers, M
Beautiful Les Paul. Mine's wine red, but I almost wish I'd gotten a cherry burst. Or at least I think that's what yours is. 🤔 The "burst" part is a bit pale, but it still looks gorgeous like a Rainier cherry.
Be nice to hear the 74 with the original reconed alnico speakers, regarding the 22uf 500v caps in ul models, i use 20uf 550 v tad audio german caps in those amps, size more or less like the originals, just done a fender 135w twin, with those caps, Best regards from sunny spain,
Thanks for weighing in. Realising Spanish Mains differ from NA, what voltage do you measure at that UL "screen" node, and the output plates? Fender's UL schematic suggests 410V with a 2700R 10W between that node and the 500V main reservoir, for 33mA preamp load including PI (which intuitively seems a bit high -- roughly double -- even with original 680R reverb driver cathode resistor). So I'm wondering what Lyle actually sees at his '79's 6L6 plates? Sure, the 2700R dropping resistor could be increased, but the "screen" node still needs his/your increased capacitor voltage against the certainty somebody someday will forget to use the standby switch.
There are equations for cap life generated by very good manufacturers (Vishay and Nichicon ) which suggest voltage higher than the caps rating is not an instant death sentence, it just results in a shorter lifespan. This suggests a 12k hour cap run 25V over its rating should last just fine, but of course YMMV ; ) I suspect many "600V rated guitar caps " (with no or < 2k hour lifespans) are equivalent to 500V 5k hour caps (or there abouts)
@@tedmich Thanks. That helps. Still wondering what these nominal 500V (1980's wall voltage) UL amps are seeing today on their power tube plates. Because I'm estimating ~16mA (four 12ax7 and two 12at7) pre-amp draw which means about a 45v drop through 2700R to the "screen" node. Or about 540v on the power plates if one measures 495v at the "screen" node. Which isn't bad as even the original Fender spec was 220uF 285v caps in series there (for 110uF @ 570v) and 40v is less than 8% over nominal tube spec with your standard 6L6GC being notoriously rugged.
@@edwardleaver7838 will measur later on what ime getting axactly bit its no where near 500v, taking into acount we have sometimes 217v at the wall here in. Spain, compared to uk which is nearing 240, makes a big difference
What the working voltage on the 1 watt vishay resistors ? ccmf they look like so 500 volts I guess. Alnico magnets can be remagnitized if the builder has the machine . Have had it done before.
I see turret strips and radial caps replacing the entire cap fiberboard and can caps in guitar amps. It’s getting pretty cheap to have small single sided PCB’s made too. I just hope it’ll all fit under the doghouse when that day comes.
Question on the caps. Since it appears the outside of the cap is a metal can attached to the negative side with a plastic wrapper cover, it appears that said wrapper is the only thing insulating 250V. (The mid-point of the two caps and the grounded case of the lower cap). This made worse by the buss wire bridge which could have some sharp points. Either I'm missing something, or it sure would be nice to see some added insulation for the capacitor mid-point connection.
You're not adding balancing resistors across the series caps for the screen supply? [Oops, I spoke too soon, hadn't watched the whole video. My apologies!]
Thanks, Lyle! I’ve been unsure of how using resistors to even out the voltage to two series caps actually works. I’m guessing the resistors let a little of the B+ bypass the cap and go to the other one. Did you calculate for what resistor to use or is the value a fairly standard choice with this technique?
BRILLIANT 😎👍 Oh and my favorite (so far) of your guitars😎👍 Just heard JJ's Arnold 54 Stratocaster pups...😎👍 What pups are in your Stratocaster...? I was right...it was the speaker... Thanks to you my ears are getting tuned😉😎👍 Thanks
Thanks. Fender used 220Ks for the first stage so I just followed suit. Anything from 100K-330K works. There are formulas, but Fender’s values are fine.
You can look up balancing resistors with series capacitors, but here's one by Vishay for instance: www.vishay.com/docs/48296/_did-you-know_aluminum-balancing_vmn-ms7375-1709.pdf
Thanks again for another insightful video. I need to as you. I won't know unless I ask. Where are your customers from are they local musicians ? Reason being is that I would love to send you my amp to be looked at, evaluated and repaired. Its a 1984 Mesa MKIIC +. I know that you're not a big fan of Mesa's . I've watched many of your repair videos and can't find one of you working on a C+. I'm sure that you know the reputation and market on C+'s. This all is a long chassis head. Components aren't cramped as in other Mesa's that I've seen you repair. Components are more relatively easier to get to. With your superior knowledge on amps, I would be very humbled if you would accept. Many C+ owners say send it to Mesa and have Mike B. go over it. I think that your channel needs a C+ repair on it. 🤗 In any event, i'll keep watching and absorbing. Blessings. Jim
I know they're annoying, so I don't like to ask questions like "what kind of silicone do you use" but, what kind of silicone do you use? That came off the board too nicely not to ask.
I'm sure there are several brands that will work fine, but do search out "neutral cure" silicone that's safe for electronics. Some of the automotive and construction-grade stuff has acetic acid which can etch into PCB boards and capacitor shells as it cures. I've never seen this happen but might as well get the proper stuff and avoid the problem entirely. Permatex makes a black neutral cure silicone that's readily available and I have an old tube of clear by Dowsil that's excellent but more expensive.
@@testing1two547 In nearly 50 years of working with audio electronics I have never seen silicone adhesive cause corrosion. The acetic acid seems to cure out very quickly which is why silicone often hardens in the tube before you get to use it all up.
![I.N "HALLUCINATION" | [Stray Kids : SKZ-PLAYER]](http://i.ytimg.com/vi/n5B5q1Hwt_U/mqdefault.jpg)
Still love my '74 Super Reverb. Built to last!! 🙏🏻✌️
Like your tenacity in locating the source of yuk!
Very cool layout for those balancing resistors and caps. Looks great and well thought out!
Thank you for this tip. I just replaced the filter caps in my 79 super. I used a MOD 500v 20uf in that position. It lasted about 2 seconds before the magic smoke came out. I am going to try replacing it with two of the 40uf 500v MODs next. Hope it works.
That felt like a master class in fixing and diagnosing; chasing down these bastard issues.
I really liked the sound of that 79 Super Reverb amp.
Thoughts on Tim Marcus’s Milkman Amplifiers?
Fantastic work! Your approach is very professional.
Thanks so much, this is a very timely video as I have a 80 ultra linear Super on my bench right now. This one has a non ultra linear unknown replacement OT in it, and I'm really struggling to get it to sound good. Someday, I hope to have at least a portion of your expertise in these matters, then I'd likely not be chasing my tail around getting nowhere. Cheers, M
Great Video! Best Alnico Speakers today are the Fane A60 or A90 IMO!!
Beautiful Les Paul. Mine's wine red, but I almost wish I'd gotten a cherry burst. Or at least I think that's what yours is. 🤔 The "burst" part is a bit pale, but it still looks gorgeous like a Rainier cherry.
Excellent
Be nice to hear the 74 with the original reconed alnico speakers, regarding the 22uf 500v caps in ul models, i use 20uf 550 v tad audio german caps in those amps, size more or less like the originals, just done a fender 135w twin, with those caps,
Best regards from sunny spain,
Thanks for weighing in. Realising Spanish Mains differ from NA, what voltage do you measure at that UL "screen" node, and the output plates? Fender's UL schematic suggests 410V with a 2700R 10W between that node and the 500V main reservoir, for 33mA preamp load including PI (which intuitively seems a bit high -- roughly double -- even with original 680R reverb driver cathode resistor). So I'm wondering what Lyle actually sees at his '79's 6L6 plates? Sure, the 2700R dropping resistor could be increased, but the "screen" node still needs his/your increased capacitor voltage against the certainty somebody someday will forget to use the standby switch.
There are equations for cap life generated by very good manufacturers (Vishay and Nichicon ) which suggest voltage higher than the caps rating is not an instant death sentence, it just results in a shorter lifespan. This suggests a 12k hour cap run 25V over its rating should last just fine, but of course YMMV ; ) I suspect many "600V rated guitar caps " (with no or < 2k hour lifespans) are equivalent to 500V 5k hour caps (or there abouts)
@@tedmich Thanks. That helps. Still wondering what these nominal 500V (1980's wall voltage) UL amps are seeing today on their power tube plates. Because I'm estimating ~16mA (four 12ax7 and two 12at7) pre-amp draw which means about a 45v drop through 2700R to the "screen" node. Or about 540v on the power plates if one measures 495v at the "screen" node. Which isn't bad as even the original Fender spec was 220uF 285v caps in series there (for 110uF @ 570v) and 40v is less than 8% over nominal tube spec with your standard 6L6GC being notoriously rugged.
Here in spain i am getting around 218v at the wall, and back in uk its around 240v so that makes a big differnce too
@@edwardleaver7838 will measur later on what ime getting axactly bit its no where near 500v, taking into acount we have sometimes 217v at the wall here in. Spain, compared to uk which is nearing 240, makes a big difference
What the working voltage on the 1 watt vishay resistors ? ccmf they look like so 500 volts I guess. Alnico magnets can be remagnitized if the builder has the machine . Have had it done before.
350V. Same as the caps.
I see turret strips and radial caps replacing the entire cap fiberboard and can caps in guitar amps. It’s getting pretty cheap to have small single sided PCB’s made too. I just hope it’ll all fit under the doghouse when that day comes.
Question on the caps. Since it appears the outside of the cap is a metal can attached to the negative side with a plastic wrapper cover, it appears that said wrapper is the only thing insulating 250V. (The mid-point of the two caps and the grounded case of the lower cap). This made worse by the buss wire bridge which could have some sharp points. Either I'm missing something, or it sure would be nice to see some added insulation for the capacitor mid-point connection.
It isn’t moving and isn’t poking through any insulation.
What year did they stop using turret boards and go to pcb's?
You're not adding balancing resistors across the series caps for the screen supply? [Oops, I spoke too soon, hadn't watched the whole video. My apologies!]
Hey @psionic audio, have you ever done a teardown \ review on a Mesa Fillmore 50 or a VHT D Fifty?
Nope. When someone brings one for repair.
Perfect man voice
Thanks, Lyle! I’ve been unsure of how using resistors to even out the voltage to two series caps actually works. I’m guessing the resistors let a little of the B+ bypass the cap and go to the other one. Did you calculate for what resistor to use or is the value a fairly standard choice with this technique?
BRILLIANT 😎👍
Oh and my favorite (so far) of your guitars😎👍
Just heard JJ's Arnold 54 Stratocaster pups...😎👍
What pups are in your Stratocaster...?
I was right...it was the speaker...
Thanks to you my ears are getting tuned😉😎👍
Thanks
Thanks Richard! Those are Kinman Traditional Mk 2s.
@@PsionicAudio
Well your Kinmans and the JJ's come from the same part of the planet🤣😎👍
Must be something in the water...?
Lyle, just curious how you come up with the 220K for the balancing resistors.
BTW, always enjoy your work and videos brother man!!
Thanks. Fender used 220Ks for the first stage so I just followed suit. Anything from 100K-330K works. There are formulas, but Fender’s values are fine.
You can look up balancing resistors with series capacitors, but here's one by Vishay for instance: www.vishay.com/docs/48296/_did-you-know_aluminum-balancing_vmn-ms7375-1709.pdf
I remember the "J" hook from the military - nice work!! Question: what type of speakers are in your shop cab??
ET65 and Veteran 30
Thanks again for another insightful video. I need to as you. I won't know unless I ask. Where are your customers from are they local musicians ? Reason being is that I would love to send you my amp to be looked at, evaluated and repaired. Its a 1984 Mesa MKIIC +. I know that you're not a big fan of Mesa's . I've watched many of your repair videos and can't find one of you working on a C+. I'm sure that you know the reputation and market on C+'s. This all is a long chassis head. Components aren't cramped as in other Mesa's that I've seen you repair. Components are more relatively easier to get to. With your superior knowledge on amps, I would be very humbled if you would accept. Many C+ owners say send it to Mesa and have Mike B. go over it. I think that your channel needs a C+ repair on it. 🤗 In any event, i'll keep watching and absorbing. Blessings. Jim
I know they're annoying, so I don't like to ask questions like "what kind of silicone do you use" but, what kind of silicone do you use? That came off the board too nicely not to ask.
I'm sure there are several brands that will work fine, but do search out "neutral cure" silicone that's safe for electronics. Some of the automotive and construction-grade stuff has acetic acid which can etch into PCB boards and capacitor shells as it cures. I've never seen this happen but might as well get the proper stuff and avoid the problem entirely. Permatex makes a black neutral cure silicone that's readily available and I have an old tube of clear by Dowsil that's excellent but more expensive.
@@testing1two547 In nearly 50 years of working with audio electronics I have never seen silicone adhesive cause corrosion. The acetic acid seems to cure out very quickly which is why silicone often hardens in the tube before you get to use it all up.
That Les Paul sounds glorious, "tearing paper sound" or not.
(Yes you are right, but it's still pronounced "peek-o-fa-rad".)