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Xin Super Macro IV: Board layout / schematic needed for repair

post #1 of 4
Thread Starter 

Trying to replace the worn-out Panasonic vol. pot, some of the traces lifted off and now I'm stuck with a "broken" SM IV.

I did snap some pix before/after the desoldering job, but I can't make out much detail from the photos (see below). I may post some more later.

I can probably reverse-engineer the damage given enough time, but right now I need a quick solution. (Symptoms: Getting low-volume fuzzy sound in right-channel only in non-crossfeed mode; crossfeed-mode adds signal to left-channel, but signal is not true left/right stereo, of course)

If anyone has photos or, better yet, a schema or board layout (Eagle) of the SM, or any other advice, I'd be grateful! 

Thx!!

Images of before and after damage:

BEFORE:

IMG_9265_100214_050718_before-repair_cropped_small.jpg

 

AFTER (magenta "trace" shows some of what tore out; I'm sure there's more damage because just a re-trace based on the magenta does not solve problem):

IMG_9290_100804_014914_traced_small.jpg


Edited by headfone - 8/5/10 at 4:27pm
post #2 of 4

I would do a continuity test of the traces, clean off all the flux so you can see everything more clearly and go from there. I have lifted a few traces while working on his amps and fixed, as you mention, by laying something else down. 

post #3 of 4
Thread Starter 

I took that bottom after shot immediately after the desolder, and it has been cleaned up. Doesn't help all that much in troubleshooting THIS case. The continuity test is only helpful if you know your endpoints. Offhand and based on the low-quality "before" shots, I don't know what those are. I believe this amps uses a 4-channel topo which may complicate things.

 

Off the top of my head, I would say the ckt is designed as this:

 

Input jack --> Vol pot --> (X-feed) --> pre-amp (op-amps) --> amp (buffer, e.g. BUF634, etc) --> Out jack

 

 

Does anyone have a schematic or Eagle layout?

 

I've had the SM IV since late 2006 and the ONLY thing I now feel it has going for it is its compact size. A lot of it is truly sub-par (e.g., SQ), especially when compared to DIY stuff. The batt rechg ckt has been going "bad" and runs a bit too hot for comfort. Dunno if that can be improved with newer technology.


Edited by headfone - 8/6/10 at 2:47am
post #4 of 4

He got away from the 4 channel because of the inherent problems. His Reference amp was better sounding. No one has a schematic, Xin never gave them out and had most of the info in his head. He would do a layout and send it out for the board to be done. 

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