tmsears
Active Member
Another victim of "the glue"..
Hi folks,
I've been a longtime lurker and seldom post, as I have very little I am able to add to this excellent forum!
I have a background in IT hardware and networking but little electronic repair experience outside of turntables. I am in the process of learning, and I have learned so much from this forum! My sole amp is a Yamaha M-4 that is acting up and needs new caps most likely due to age among other things I am sure; it has sadly become unusable in it's current condition.
In my infinite wisdom I decided to get a "substitute" integrated amp while I learned how to work on the M-4 at a leisurely pace. I wanted tot take my time so as to not risk messing it up. I sold off a turntable and used the funds to by an A-1000 off of the 'bay'. I corresponded with the seller and found out that he had bought it new, always babied it, and didn't want to part with it but the wife.., etc.
Believe it or not, it all was true! The amp arrived packed extremely well, in immaculate condition, complete with manual. I blew the dust out of it, hooked it up to a dim-bulb tester I made, plugged in a pair of MonoPrice headphones, and played Huey Lewis on my old crappy phone through it. At first I only got one channel, but I was able to get both going by tapping on the relay.
The amp sounded wonderful, for exactly 38 minutes. That's when I heard a 'brrrrrtttt' sound in the headphones as I watched the bulb in the DBT lite up full strength.
I opened it up and well, a pictures at this point will save me from boring readers anymore than I have already. I apologize for the picture quality in advance:
Thanks to this site I know that this is the dreaded "glue" and not the capacitors simply leaking. I found more glue on the "equalizer" and tone boards but the glue there has not gone bad...yet.
So it looks like I am going to have to repair my substitute amp so that I can repair my M-4. I have been wanting to get into repairing vintage amps as a hobby but I didn't know my initiation was going to be a trial by fire .
So the first two questions that I know to ask is, 1) on the blue resistor that has the corroded leg: there is only one other resistor colored blue like that in the amp, it is the same value, so I assume it is the "twin". They are R133, 134. 820 Ohm:
2) The 680uf caps, and I guess the 330uf's next to them, are they signal path or power? I have the service manual but I am still learning how to read schematics, so apologies for this and future ignorance.
Oh, and the obligatory 'resistor bbq' that is equalizer board 14 (thanks go to @avionic for the replacement tip!):
I have a used 100 Mhz oscilloscope, two crappy home depot DMMs, a Chinese component checker and a Weller magnastat (don't laugh) and I ain't scared, but not foolish (I hope).
Any advice would be greatly appreciated.
Hi folks,
I've been a longtime lurker and seldom post, as I have very little I am able to add to this excellent forum!
I have a background in IT hardware and networking but little electronic repair experience outside of turntables. I am in the process of learning, and I have learned so much from this forum! My sole amp is a Yamaha M-4 that is acting up and needs new caps most likely due to age among other things I am sure; it has sadly become unusable in it's current condition.
In my infinite wisdom I decided to get a "substitute" integrated amp while I learned how to work on the M-4 at a leisurely pace. I wanted tot take my time so as to not risk messing it up. I sold off a turntable and used the funds to by an A-1000 off of the 'bay'. I corresponded with the seller and found out that he had bought it new, always babied it, and didn't want to part with it but the wife.., etc.
Believe it or not, it all was true! The amp arrived packed extremely well, in immaculate condition, complete with manual. I blew the dust out of it, hooked it up to a dim-bulb tester I made, plugged in a pair of MonoPrice headphones, and played Huey Lewis on my old crappy phone through it. At first I only got one channel, but I was able to get both going by tapping on the relay.
The amp sounded wonderful, for exactly 38 minutes. That's when I heard a 'brrrrrtttt' sound in the headphones as I watched the bulb in the DBT lite up full strength.
I opened it up and well, a pictures at this point will save me from boring readers anymore than I have already. I apologize for the picture quality in advance:
Thanks to this site I know that this is the dreaded "glue" and not the capacitors simply leaking. I found more glue on the "equalizer" and tone boards but the glue there has not gone bad...yet.
So it looks like I am going to have to repair my substitute amp so that I can repair my M-4. I have been wanting to get into repairing vintage amps as a hobby but I didn't know my initiation was going to be a trial by fire .
So the first two questions that I know to ask is, 1) on the blue resistor that has the corroded leg: there is only one other resistor colored blue like that in the amp, it is the same value, so I assume it is the "twin". They are R133, 134. 820 Ohm:
2) The 680uf caps, and I guess the 330uf's next to them, are they signal path or power? I have the service manual but I am still learning how to read schematics, so apologies for this and future ignorance.
Oh, and the obligatory 'resistor bbq' that is equalizer board 14 (thanks go to @avionic for the replacement tip!):
I have a used 100 Mhz oscilloscope, two crappy home depot DMMs, a Chinese component checker and a Weller magnastat (don't laugh) and I ain't scared, but not foolish (I hope).
Any advice would be greatly appreciated.
Last edited: