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Vintage Synth Repair

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Re: [vintagesynthrepair] Re: Sh-101 problem

2008-04-02 by Nik Sargeant

The main CPU is an 8049 .. so I would check for signs of life in the CPU by putting a scope on pins 2,3 (for the crystal oscillator) and the key signals like -RD, -PSEN, -WR and ALE on pins 8,9, 10 and 11.

If that works, you might wish to go forwards from there, see that the signals are getting to key components like address latches, ROMs, tristate buffers and so on.

Nik

inocencio66 wrote:

--- In vintagesynthrepair@yahoogroups.com, Philip ...>
wrote:
>
> Dont know, but i'd start by checking the power supply.
>
> Phil.
>
> --- inocencio66 ...> wrote:
>
> > The SH-101 powers up normally but the key transpose
> > LED stays lit and
> > all the buttons do not work. And it doesn´t make any
> > sound.
> > Is this a common and easy problem to fix?
> >
> > Thanks.
> >

Yes, but what to check? The service manual is not of much help; well at
least not for me: no checkpoints nor voltage references...

It seems to be the CPU giving trouble. What to look for?

--
Regards,

Nick Sargeant

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