Hi andjur78,
I've also seen that conductive glue. It is the cause of the corrosion as well. You should find that it will chip away for the most part. The plyable stuff needs to be cut and yanked out. I bet that's your problem.
I remove this whenever I see it. The darker brown it is, the lower the resistance tends to be.
-Chris
I've also seen that conductive glue. It is the cause of the corrosion as well. You should find that it will chip away for the most part. The plyable stuff needs to be cut and yanked out. I bet that's your problem.
I remove this whenever I see it. The darker brown it is, the lower the resistance tends to be.
-Chris
I second all the comments on the brown glue.That stuff is bad news.It always causes me problems,especialy when it's old. 🙄
There's a similar yellowish kind I've seen a few times,but havn't noticed any problems with it (yet).
There's a similar yellowish kind I've seen a few times,but havn't noticed any problems with it (yet).
The caps dont actually look that bad. I have had seen the leaking (powdery) electros before, but these "look" ok. But when is a cap really a cap? Maybe these are cheap derrivitaves of the real electrolytic capacitor as we know (have known) it??
(I,m sure there would be a website dedicated to electro caps and brands out there somewhere)
I don't know exactly what that brown gunk is but it sure does show up in alot of audio gear that has been made in China .
All the AMC stuff I have seen over time uses this glue around the base of caps and Xtals. "Well done" for Welltronics!!
...maybe it is some kind of space age vegemite that astronaughts use on their sanwiches😀
Anyway,I will clean the pcb, replace all electros and reassemble it this week. Then its soak test time again.
Stand back...
(I,m sure there would be a website dedicated to electro caps and brands out there somewhere)
I don't know exactly what that brown gunk is but it sure does show up in alot of audio gear that has been made in China .
All the AMC stuff I have seen over time uses this glue around the base of caps and Xtals. "Well done" for Welltronics!!
...maybe it is some kind of space age vegemite that astronaughts use on their sanwiches😀
Anyway,I will clean the pcb, replace all electros and reassemble it this week. Then its soak test time again.
Stand back...
Hi andjur78,
The glue is used in PCB manufacture to hold the heavier components in place during soldering. I've seen it on Sony and NEC made PCB's as well. I think this is your only problem. Other components should be fine as long as the lead isn't corroded too much.
Someone once told me this wonderful stuff was called "Sonybond". I can't say for sure, but I know that Sony never admits to anything when they make a mistake.
-Chris
The glue is used in PCB manufacture to hold the heavier components in place during soldering. I've seen it on Sony and NEC made PCB's as well. I think this is your only problem. Other components should be fine as long as the lead isn't corroded too much.
Someone once told me this wonderful stuff was called "Sonybond". I can't say for sure, but I know that Sony never admits to anything when they make a mistake.
-Chris
Ok for all who are interested: It is not the caps!!!
I Replaced all electros, cleaned the pcb and went over every solder joint and the fault is still exhibited.
Now I will home in on the front end differential pair.
If anyone is interested in posts of the ongoing servicing of this amp please let me know and I will continue to post any updates.
I Replaced all electros, cleaned the pcb and went over every solder joint and the fault is still exhibited.
Now I will home in on the front end differential pair.
If anyone is interested in posts of the ongoing servicing of this amp please let me know and I will continue to post any updates.
Hi andjur78,
Well, I'm always interested. I was hoping it was the "glue". That would be a cheap fix.
-Chris
Well, I'm always interested. I was hoping it was the "glue". That would be a cheap fix.
-Chris
Should we start a pool? I guess it's too late now.
It looks like a junction breaking down in a transistor. Normally a 2SC458 is at the bottom of that, or an early J-fet. There are none of these here.
-Chris
It looks like a junction breaking down in a transistor. Normally a 2SC458 is at the bottom of that, or an early J-fet. There are none of these here.
-Chris
Its never too late!
Audio will always be here😉
This repair is a real pain...one would feel like a large reward after this nailing one ...:cool
I will remove the front end diff pair NPN package and substitute for another known working one. This is a Sanyo device 2SC3067
130 volt , 50mA.(google finds the spec sheet)
I don't know of any equivalents to it as yet.
Will keep all informed...
Audio will always be here😉
This repair is a real pain...one would feel like a large reward after this nailing one ...:cool
I will remove the front end diff pair NPN package and substitute for another known working one. This is a Sanyo device 2SC3067
130 volt , 50mA.(google finds the spec sheet)
I don't know of any equivalents to it as yet.
Will keep all informed...
Hi andjur78,
I'm lost. What is the locator number for that part? All I saw were single TO-92 parts. 2SC1681, 2SA841 types are used as the original parts. 60V, 50 mA, 200mW, hFE 450 ish. This is a low noise part. 2SC1775A and 2SA872A are good subs. Do not waste your time with ECG or NTE parts. The cross reference book is useless, don't use it.
You can use almost anything to substitute to see if that's the problem and get the correct part later.
-Chris
I'm lost. What is the locator number for that part? All I saw were single TO-92 parts. 2SC1681, 2SA841 types are used as the original parts. 60V, 50 mA, 200mW, hFE 450 ish. This is a low noise part. 2SC1775A and 2SA872A are good subs. Do not waste your time with ECG or NTE parts. The cross reference book is useless, don't use it.
You can use almost anything to substitute to see if that's the problem and get the correct part later.
-Chris
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