[sdiy] Re: Broken SH-101 - ideas wanted...

[Florian Anwander]

Ok, everyday you learn something new...

After an extensive session of measuring and tracing voltages and signals 
(btw: thanks to many kind and helpful people who sent advices) I took my 
philatelists lense and started looking for broken or cold solder joints 
or broken traces. With the first look at a connector I was worried, 
because I could see in the lense something between the pins of the 
connector, that looked like "microscopic mildew". It was not visible 
with bare eyes (at least with my eyes, which will need a reading glass 
sooner or later...). So I picked a "trouble free" area on the pcb and 
tried to clean it with alcohol. Bang... the surface became white, muddy 
and sticky. It feeled like the remains of old gaffer tape. I tested with 
a similare area of the sliders pcb, and there was nothing like that.
Now I did a first try with alcohol and a tooth brush and the first 
(very intermediary) result looked like that:
http://fa.utfs.org/diy/rolandsh101/surprising-SH-101-board.jpg

It is really unbelievable. This is not the first pcb that I have the my 
hands and I have seen a lot of pcb which had been soaked with beer, 
coke, cat pee and other stuf, you and I wo not want to know. But I never 
have seen a pcb covered with something like that, which was definitely 
not visible while several hours of work.
I only wondered a little bit, why the mainboard pcb was slightly darker 
than the other pcbs.

I did not clean the pcb completely until now, but already the CPU seemes 
to come back to life again.

This story will be continued the next days...


Florian

Florian Anwander wrote:

> Hello,
> 
> I have here a Roland SH-101, which does not make sound.
> 
> The CPU starts the boot, but does not reach the testmode 
> (Load+Keytranspose while power on). When I switch the synth on, first 
> the Keytranspose LED is lit, and a second later the Hold LED is lit also 
> - both LEDs stay on and cannot be changed. And nothing further happens.
> 
> Also the CEM3340 does not oscillate (checked with scope at the outputs 
> of the chip).
> The Noise works ok on the mainboard (checked with scope and audio at the 
> buffering OpAmp), but does not reach the VCF!
> VCF, LFO, ADSR work fine (checked with full resonance and external CV 
> and Gate).
> 
> All supply voltages read correct values.
> 
> Any suggestions?
> 
> 
> Best regards Florian
>