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  1. The replacement resistors finally arrived,...

    The replacement resistors finally arrived, replaced R87 and I now get the perfect sin I'm feeding into the power amp on the speaker output, major success! I still need to test it properly and then...
  2. Ok, sounds like a plan... it's not just erroneous...

    Ok, sounds like a plan... it's not just erroneous crackles unfortunately, the negative side of a scoped sin is chopped off too, and the whole sound has a sort of fuzzy bit-crushed sound as it fades...
  3. Ah... as if by magic I've found that r87 is...

    Ah... as if by magic I've found that r87 is fused! Everything else checks out on the board as far as I can test in circuit. There are a few tolerances on the edge but I think they are basically other...
  4. Thanks, yeah I sort of knew that but was allowing...

    Thanks, yeah I sort of knew that but was allowing myself to get confused with d28 and d29, now I see they aren't forward biased by the signal, on the input side, but probably from the rails on their...
  5. Thanks, I just read the enormous thread over at...

    Thanks, I just read the enormous thread over at DIY audio and those parts came up there, too. I think after reading 300 ish posts over there I have a bit of a better understanding of what's going on...
  6. Thanks, freeze spray on the way.. none of the...

    Thanks, freeze spray on the way.. none of the transistors are overly hot after use however, though I'll still go through with the spray when it arrives.

    I know the lack of advice is probably down...
  7. Hmmmm, so, a lot of negative DC voltages getting...

    Hmmmm, so, a lot of negative DC voltages getting somewhere they shouldn't? Some kind leaky capacitor on the negative side perhaps?

    Yeah I'm learning that!! It's just seems a mess of stuff that all...
  8. OK... I don't know enough to really interpret...

    OK... I don't know enough to really interpret what I'm getting back here, though it's definitely illuminating, learning tonnes as ever.

    I wondered if anyone could point me in the direction of a...
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    Yeah.. I know what you mean... With the amp I...

    Yeah.. I know what you mean...

    With the amp I was working on, a Laney VC-30 for the record, I got some advice and was told it was a high voltage but incapable of giving out much current, so I...
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    Good reading, thanks! I repaired an amp a...

    Good reading, thanks!

    I repaired an amp a little while ago and found that if I removed the ground reference for the main PCB (I had to remove it as it connected to the leg of a big filter can-cap,...
  11. I'm starting to think that's what it is, though I...

    I'm starting to think that's what it is, though I didn't get a reading through the tiny piece I had left. It didn't peel off in lumps though, I had to scrub it up and scrape away so hard to test...
    ...
  12. Thanks a tonne for your great reply! I have to...

    Thanks a tonne for your great reply! I have to admit on reading back my final/simplified question it did seem a bit obvious when I awoke the next day! I had reached the conclusion that my devices are...
  13. Can definitely-bad capacitors test ok in some situations?

    Ok, so I opened up an old teac cassette deck that was completely dead.

    The 3 power electrolytics, or at least one of them, had spilled a messy brown deposit over everything in the area. I removed...
  14. Ok cool, thanks. Yeah, no problems with that this...

    Ok cool, thanks. Yeah, no problems with that this end, I've been using chassis ground and my load is just connected as the speaker would be. But good learning thinking through why that was a point...
  15. Yeah...I see that, I guess once I replace C42...

    Yeah...I see that, I guess once I replace C42 then I can move on and tick the OP amp circuit off the list of suspects...



    Cool, I see what you mean, but not too sure how that will affect my...
  16. Thanks, I've had a good root around and...

    Thanks, I've had a good root around and resoldered everything. The only thing out of spec was c42 which measured about 35pF. I'm can't get my head around how that circuit actually works, but figure...
  17. Hi guys, so after looking around and getting...

    Hi guys,

    so after looking around and getting my head HALF around what's going on, I've started to zone in on some stuff that I could do with some help on..

    For now I'm curious about this; the...
  18. Thanks, I figured there was a little I was...

    Thanks, I figured there was a little I was missing, I wasn't triggering at all, just running it in 'normal', on AC trigger mode I can get a stationary drawing, and on the 'waveform icon' I can get it...
  19. OK! I'm enjoying this scope thing, seems much...

    OK! I'm enjoying this scope thing, seems much more pragmatic than just having a multimeter and no real idea of how this circuit is supposed to work! Learning a tonne..

    I've found some oddities all...
  20. Thanks, understood, lets see what I get

    Thanks, understood, lets see what I get
  21. Thanks! I was meaning more though, what voltage...

    Thanks! I was meaning more though, what voltage should I output with a test oscillator? By the diagram the pre amp out is giving 91mV, and one it goes through the first op amp in the power amp itís...
  22. Thanks all. I received the scope and have got to...

    Thanks all. I received the scope and have got to know it and calibrated it, as far as the basic calibrations in the manual outline. It's pretty simple all in all isn't it? I could get the basics and...
  23. I thought about it but bench space is a premium...

    I thought about it but bench space is a premium and I was going to run a cable from my mixing desk on the next table, generating a wave from Logic or similar.. that seems to be the cheapest and...
  24. Thanks! I bought it, I figured for less than £100...

    Thanks! I bought it, I figured for less than £100 and 100% feedback I may as well go for it ;) I've always loved those things since I was a kid in science class anyway, so to have an old analog one...
  25. So I've been looking for an oscilloscope, I don't...

    So I've been looking for an oscilloscope, I don't imagine going too deep into measuring digital waveforms and the like just yet, so should something like this be enough for working on amps? I'm NOT...
  26. OK, yeah imagined it might need a bit more...

    OK, yeah imagined it might need a bit more analysis but wasn't sure.. well, I could get into the idea of buying an oscilloscope, I've always wanted one but so far it wouldn't have offered much help...
  27. Got it working, just needed the new jack sockets...

    Got it working, just needed the new jack sockets and PCB work around that area, attached is a pic of the board after repair. It's not pretty but should be solid (feel free to correct/point out...
  28. Fender Frontman 212r sound breakup and crackles diagnosis

    Hi all

    So after fixing one 212r I find myself with a second with a more curious symptom. The amp works but breaks up in an almost bitcrushed, digital way on the fadeout of chords, and sounds...
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