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  1. 426vdc is While running, and as you know there is...

    426vdc is While running, and as you know there is a brief exposure to higher voltage (peaks briefly at 540vdc) on startup. I will order a few 600v 47uf caps. It's the first one off the B+ that will...
  2. Only a power and an output transformer, no...

    Only a power and an output transformer, no chokes. The tubes are 6J7, 6KS7, 6SN7, and two 6L6s.

    Thanks for any help !
  3. Till this point I haven't had the confidence to...

    Till this point I haven't had the confidence to draw any circuit, but I think your advice is good, and I will attempt it as part of my learning and initiation. Probably have something later today....
  4. 6.8 vac, again a bit high, and I think you are...

    6.8 vac, again a bit high, and I think you are correct about the wall voltage being a part of the problem. I do have an inexpensive surge protector that automatically limits wall voltage to 114vac...
  5. I checked the 6L6 coupling caps and no DC voltage...

    I checked the 6L6 coupling caps and no DC voltage leaking from one end to the next. Those are the best looking caps of the lot, so I left them in, but I will take your advice under advisement just...
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    I think that is the problem here, and you are...

    I think that is the problem here, and you are correct.

    I have quite a few 6V6 metal can tubes, and they work splendidly in a couple of my Valco amps, but I believe this amp is stretching the...
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    I think I ran into just that type of problem when...

    I think I ran into just that type of problem when I got the amp up and running tonight. I added some more resistance to the screen power supply node, and that seemed to quite things down a bit. I...
  8. Do you have the schematic for this amp ? ...

    Do you have the schematic for this amp ?

    That's what I was looking for in my other post.

    If you have the schematic, please post it, and I will be eternally grateful !

    And once again, Thanks...
  9. Tried again, this time using alligator clips...

    Tried again, this time using alligator clips attached to the leads so I could get a really good "Bite" on the wires of the two resistors, and they are out of the amp entirely... Nothing, not using...
  10. I will try to do just that. I actually got a...

    I will try to do just that. I actually got a better view of everything just tonight. I am not quite as up on this stuff as I might seem, LOL, but maybe that would help. One thing I did was pull the...
  11. 224 ohms each side spot on. I just added some...

    224 ohms each side spot on. I just added some more resistance to the cathode resistor from 180 ohms to 230 ohms. I think I should have gone a bit further, as now one of the tubes is still at around...
  12. Runaway current draw from single 6L6 tube

    Just got an old RCA amp the other day, no schematic looked everywhere including here...

    Things were going well tonight testing, and I actually got to play through it for about a half hour, but...
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    Thanks for your suggestion, and that went through...

    Thanks for your suggestion, and that went through my mind, but I also revere certain things that might have been done already in the design of the amp, perhaps to minimize noise and hum, so I am a...
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    Thanks Enzo, I installed the cap atop the 6J7....

    Thanks Enzo, I installed the cap atop the 6J7. Exotic is a relative term, as I am currently used to working on comically simple valco amps, almost exclusively !

    Question : there are two big blue...
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    Thanks for your help, but there is a complication...

    Thanks for your help, but there is a complication for the preamp section and I think they were using two channels with different sensitivity and filtering. That is the 6SK7 and the 6J7 I believe are...
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    Thanks for what you added, it helped a bit. I...

    Thanks for what you added, it helped a bit. I decided to take this one as a "project" and I believe I will need to strip out some of the exotic Hi-Fi circuits in favor of a more simple guitar amp...
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    RCA 6L6 Mono Amp # MI-6599

    Need help with schematic for an RCA 6L6 mono tube amp, model (or chassis not sure) MI-6599

    Could have been part of a PA or perhaps even an ancient TV, not sure.

    Here a pic of one I found doing...
  18. Thanks for figuring that out Helmholtz, I rely on...

    Thanks for figuring that out Helmholtz, I rely on you to be the brains behind whatever low level "Experimental" stuff I am doing at this point ! :)

    By the way, part of my mixed heritage is from...
  19. Thanks Bloomfield. I think I am going to try this...

    Thanks Bloomfield. I think I am going to try this and see how it works out, but on one of my "rolling test lab" hi-fi chassis amps first. I have a few that run 6J5 tubes in V1, so I believe I can sub...
  20. Nice ! Always learn something new here !

    Nice ! Always learn something new here !
  21. Does the Filld Coil in this National amp act as a choke ?

    I asked that question about another one of my old amps a while back (Supro Supreme circa 1949) and the answer was no for the below Supro amp :

    56111



    But for the amp below (A Valco cousin...
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    Ok, I see your point. I believe it also has to do...

    Ok, I see your point. I believe it also has to do with the way you dress the crimp connection, if at all, and if corrosion on the metal to metal surfaces gets hold of it because of touching the...
  23. Not sure if it's the same thing, but someone in...

    Not sure if it's the same thing, but someone in the distant past took the three inputs and assigned one to one side of the 6SN7, and the other two to the other side of the tube. They also have two...
  24. Wow, crazy how little you gain, but that's why...

    Wow, crazy how little you gain, but that's why you don't see it that often, and that's why they came up with more powerful tubes like the 6J7, 6SQ7, and the newer noval 12AX7.

    I think I am going...
  25. I might switch the amp back to a 6J7 preamp tube...

    I might switch the amp back to a 6J7 preamp tube (pentode). But first I have to see if that added circuit is of any use, and if it helps the amp then I will leave well enough alone.

    I'm a bit...
  26. Nice, thanks for taking the time ! I think I...

    Nice, thanks for taking the time ! I think I understand it a lot more now, and it makes sense based on my limited knowledge already.

    I have to get a scope, but I'm afraid it will take up too much...
  27. Perhaps... But there was a mysterious circuit...

    Perhaps... But there was a mysterious circuit addition to the amp using one of those six flat prong plugs. The circuit has an old Long Plate RCA 12AX7 and a few caps and resistors in it, and it looks...
  28. So do you think I am better off running one...

    So do you think I am better off running one triode into the other ? I have this arrangement on another amp of mine :

    http://www.oldfrets.com/Valco/Schematics/valco_1212.pdf
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