As you may have guessed, my Sugden Au51p, after a rather lovely 18 months enjoying Pete Maddex's recap, is on the blink.
I noticed a bit of crackling during explosions on sci-fi films; tracking down a handy youtube bass sweep
(
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shows that at (say) 20-30 Hz, at reasonable volume I get a lot of high frequency crackle. At very low volume things are OK.
I tried swapping over inputs, and speakers, and am certain that the fault is right channel only.
Following some email advice from Pete I have physically checked all the capacitors that he replaced for lifted tracks, and found nothing.
I have also checked with my multimeter that all tracks leading to/from the caps show continuity, and that all tracks that might have been bridged show NO continuity.
Given the symmetric power rails, and NPN/PNP transistor distribution, it seems reasonable that the amp is a traditional biased/AB. Assuming that I only have one fault, I could use a oscilloscope on the output waveform, and infer which "half" of the board is faulty. But I have no scope. (I also have no signal generator, although bizarrely, due to extreme good fortune, I do have a varaic https://www.pinkfishmedia.net/forum/threads/identify-a-variac.210736/ )
Am I wasting my time trying to diagnose with so little test equipment, or are there useful/simple techniques of which I am ignorant?
BugBear (kinda' desparate)
I noticed a bit of crackling during explosions on sci-fi films; tracking down a handy youtube bass sweep
(
shows that at (say) 20-30 Hz, at reasonable volume I get a lot of high frequency crackle. At very low volume things are OK.
I tried swapping over inputs, and speakers, and am certain that the fault is right channel only.
Following some email advice from Pete I have physically checked all the capacitors that he replaced for lifted tracks, and found nothing.
I have also checked with my multimeter that all tracks leading to/from the caps show continuity, and that all tracks that might have been bridged show NO continuity.
Given the symmetric power rails, and NPN/PNP transistor distribution, it seems reasonable that the amp is a traditional biased/AB. Assuming that I only have one fault, I could use a oscilloscope on the output waveform, and infer which "half" of the board is faulty. But I have no scope. (I also have no signal generator, although bizarrely, due to extreme good fortune, I do have a varaic https://www.pinkfishmedia.net/forum/threads/identify-a-variac.210736/ )
Am I wasting my time trying to diagnose with so little test equipment, or are there useful/simple techniques of which I am ignorant?
BugBear (kinda' desparate)