[sdiy] Advices for restoring an old Roland SH2

[Jean Bender]

Hi !
thanks for the tips.
For the mains hum, i'm recapping the psu board, and i've changed the
main transformer from 110V to 220v. We'll see what happens, it's not
finished, i don't have all the caps. As for all psus, some of them are
electrolytics, and the others are mylar's one. Could i change these
mylar caps for MKT's one ? Is there a big deal to do it ?

And then, i haven't found nothing yet for the main out lack of gain
amplification. The ground trace seems to be ok, not burnt. I'll take
time to check the schematics and the op amp..

Thanks again,
J.

2016-02-27 19:53 GMT+01:00 Chris Juried <cjuried at yahoo.com>:
> I have seen this issue before as well Richie. The ground trace, to the 1/4"
> chassis mount connector, is susceptible to excess current and can become an
> open-circuit rather easily.
>
> Sincerely,
>
> Chris Juried
> Audio Engineering Society (AES) Member
> InfoComm-Recognized AV Technologist
> http://www.JuriedEngineering.com (Juried Engineering, LLC.)
>
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> ________________________________
> From: "rburnett at richieburnett.co.uk" <rburnett at richieburnett.co.uk>
> To: Jean Bender <lofideadbeat at gmail.com>
> Cc: synth-diy DIY <synth-diy at dropmix.xs4all.nl>
> Sent: Saturday, February 27, 2016 9:12 AM
> Subject: Re: [sdiy] Advices for restoring an old Roland SH2
>
> Maybe someone has plugged it into a faulty "live" valve amplifier or
> something and it has burned off the ground trace to the line out jack on
> the back of the synth.  That's what I think had happened to my SH-09
> when I got it.  The ground trace to the line out jack was completely
> vaporised off the little board that the jacks are mounted on.  The only
> thing I can imagine that would cause that kind of damage is having mains
> power plugged into it somehow.  Fortunately soldering a wire along the
> route of the previously fused track, brought the line out jack back to
> life and removed the 50Hz buzz from the output.
>
> It's quite a thin trace from what I remember so probably wouldn't take
> THAT much current to burn it open-circuit.  I'm sure things would have
> been different if the jack sockets had been electrically connected to
> the chassis, instead of having little plastic insulating washers around
> them where they pass through the metal enclosure.
>
> -Richie,
>
> On 2016-02-27 13:28, Jean Bender wrote:
>> Hi !
>>
>> I've got a Roland SH2 to fix. It's working propoerly, except a "buzz"
>> that appear around the 50hz  : this buzz is always here once the synth
>> plugged. I imagine a problem around the power distribution ? I should
>> chek all the caps and replace some of them ?
>>
>> Also, the main output has no gain, and i have to use the headphone
>> output. Would somebody have an idea about that ?
>>
>> Thanks for any advice or answer !
>> Best.
>> J.
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-- 
Jean Bender

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