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

charlie wallace charlie at finitemonkeys.com
Sun Sep 29 20:07:42 CEST 2013


frys carries some SMY stuff if you have one. though usually 1206

On Sun, Sep 29, 2013 at 9:13 AM, Pete Hartman <pete.hartman at gmail.com> wrote:
> So what would cause digital crosstalk, in only one channel, for a
> synth that presumably didn't have this problem when it was new?
>
> The hint appears to be lost on me ;-)
>
> The only thing that occurs is tracing the path and seeing where it
> comes nearest to digital lines that the other channel does not...?
>
> I think I can step away from the idea of "re-capping" the synth; I've
> heard other people talk about doing such things, and I did fix an old
> Roland S-10 which had NO output by replacing a handful of likely
> seeming caps, so that's where I was coming from with that.  Clearly
> the weight of experience is that doing so willy nilly is a bad idea
> (and my own experience with other hardware at a larger scale would
> argue the same), and I'm not married to the idea.
>
> I appreciate everyone's suggestions, and I'll keep the list posted as
> to my progress; of course it will be a bit before I can proceed on, as
> I have no 10uF SMT caps handy, and I'm very doubtful I'll find them at
> Radio Shack.
>
>
>
>
> On Sun, Sep 29, 2013 at 8:21 AM, Magnus Danielson
> <magnus at rubidium.dyndns.org> wrote:
>> On 09/29/2013 04:36 AM, 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.
>>>
>>> First guess is then replace IC175 (we'll see how well that works for
>>> me; I'm not much good with wire trap connectors and there are LOTS of
>>> cables all around this section of the board).
>>>
>>> I'm curious if any of the more experienced members have an opinion on that.
>> Are you sure that it's a cap problem?
>> I would look at cross-talk from digital lines. Caps can help mitigate
>> that, but you need to look at it from a signal integrity way rather than
>> just audio by itself.
>>
>> That only one channel has the problem is a great hint.
>>
>> Cheers,
>> Magnus
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