[sdiy] "re-cap" when it's SMT?

The Laboratory of Sound info at labofsound.com
Sun Sep 29 12:08:44 CEST 2013


I recently repaired an XP-50 in which the right audio channel wasn't 
working anymore. I replaced all the electrolytic caps in the analog 
signal path on the main board. Two had been leaking and nearby copper 
traces got corroded by it so that there was no more continuity. After 
rewiring these traces, right channel audio was restored. Hope this 
helps. Btw, the opened copper traces were really tiny, you will need 
magnification to work on them.

Cheers,

Jack

-- 
The Laboratory of Sound
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2341 JE Oegstgeest
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T +31 71 517 0230

www.labofsound.com


On 2013-09-29 09:45, Gordon JC Pearce wrote:
> On Sat, Sep 28, 2013 at 09:36:28PM -0500, Pete Hartman wrote:
>> To follow up on this....
>> 
>> I did audio probes, and found:
>> 
>> Only the left channel has the problem.
>> The D/A chip (IC19, UPD63200GS-E2) left channel out (pin 11) has no
>> sign of hiss.
>> IC175, a 10uF SMT electrolytic--appears to be for blocking DC--has a
>> bit of corrosion on the far side, and there is hiss there.
> 
> I haven't really found that electrolytic capacitors fail, and in
> general the results of people "re-capping" gear that is otherwise
> working okay tend to be pretty dismal.  It *does* sound like this one
> may have a problem, though.  Whip it out and replace it, and see what
> happens.
> 
> From experience I've found that electrolytic capacitors really only
> fail in cheap crappy switched-mode PSUs (Amstrad SRD1000 anyone?).
> Disc ceramics and their surface-mount versions are the ones to watch,
> because as well as being thermally unstable they go leaky and upset
> your DC conditions.
> 
> And we all know about tantalum bead decoupling capacitors, right?




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