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2275 refurb troubleshooting

JLS

JLS

New Member
Howdy. I am in the middle of a 2275 refurbish and have discovered a few issues. With the generous assistance of runningdog, I've done a bunch of troubleshooting and eliminated some issues and am in the process of eliminating others (see the full process with video and photos here: https://audiokarma.org/forums/index.php?threads/2275-broken-j708-wire-on-p700-board.891548/). Here are the main concerns at this point:

1)Tone Board. I suspect there may be issues with my soldering. I've replaced all of the caps. The first time, I attached the CE11 cap to the wrong spot, then when I discovered this and went to move it, saw that it had bulged. I then replaced it with a new one and the signal is pretty weak. Once I swap in a working board, I will confirm this board as an issue. What are my options if this is the case? New board? Keep checking soldering issues?

2) R Amp. When the right amp is plugged in, the relay does not click and there is no sound. The L amp works when the R amp is unplugged. What should I be looking for here?

I am on the hunt for an Oscilloscope to borrow and may have one in a week or so, which will help. I've never used one before. Once I get it, what should I do?
 
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Swapped in a working Tone Board today and it appears to have solved the sound issues I was having before. Now I just need to figure out what's happening with the R amp.
 
These two pictures have arrows pointing to suspect solder joints. Or it could just be the lighting.


This one I'd want to remove the solder, check to see if the foil trace has lifted, and if not then solder it back in with fresh solder.
2275 PE01 JLS foil 2.JPG

This one looks like the solder has not flowed onto the capacitor lead.
2275 PE01 JLS foil 3.JPG
 
I assume you mean the foil that surrounds the holes on the foil side? I believe it has lifted in that spot. It was hard to get the solder to adhere to the board. What should be done in a case like that?

I did replace CE37 and CE38 and as far as I know they are both polarized (have + and - leads).
 
The lines and pads of copper foil are referred to as "traces". When a trace is lifted, most often at a pad, then it needs to be repaired to insure the component is making solid contact with the rest of the trace. A repair can be elegant, where the broken trace/missing pad are replaced and a grommet installed in the hole. There is a thread on AK showing repairs by @catrafter that are truly elegant.

A jumper lead is a common workaround. The lead runs from the component lead, along the trace, and is soldered to the next component on the trace.

Get as much solder as possible off it so we can see what it looks like?
 
JLS said:
I did replace CE37 and CE38 and as far as I know they are both polarized (have + and - leads).
Click to expand...

If the capacitors are bi polar then they will say BP on them. CE37 and CE38 should be BP. I'm not sure installing polarized caps is enough to keep the board from working but they should be replaced with BP caps.
 
The film caps will work. I use a Nichicon MUSE bi polar electrolytic capacitor in this location.

Mfg part number UES1H4R7MEM. Mouser is out of stock, Digikey has them.
 
SOLVED

So a friend, who is an electrical engineer, (duh. I should have asked him first!) has a scope and was able to help me troubleshoot my two problems above.

1)Tone Board. Although it took a while, the issue was definitely solder-related. There were some funky traces and beginner's soldering mistakes. We cleaned it up and got it working.
2) R Amp. This also turned out to be a soldering issue. Same as above. Some funky traces and not solid contacts.

I was able to successfully recap the L Amp with no issues and am debating continuing on to the Phono Amp or to just quit while I'm ahead and tackle that another day.

Regardless, this was made a TON easier with the assistance of @runningdog. A stellar representative of the generosity and knowledge of this board!
 
It's so good to hear that it is working again! Congratulations on tracking down and fixing the issues.
 
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