[sdiy] Siel OR400 power supply busted

[Steve Lenham]

Hi Maeghan,

> I got the power supply working :)
>
> But the synth isn't working. I'm gonna guess that even though the
> power wasn't being distributed to the rest of the circuitry, that
> when the short circuit happened … it arced and friend some
> components.
>
> THe synth is now turning on, and getting the proper voltages (not
> perfect but .1 off on some of the leads) … no sound. One of the
> chips, the LM13700 has a broken leg but according to Bob Wiegel over
> on sounddoctorin, that would take out the brass section.
>
> Here's my question: should I consider the synth dead?  or is this
> something that can be fixed?

It can certainly be fixed. The question is, are you equipped to fix it? 
There are several things in your favour - the schematics are available, 
the synth in question is relatively simple and you have some experienced 
people here on the list willing to help.

In a way, painful as it might be, you are getting the best crash course 
in synth repair that you could wish for. You have already come a long 
way and must have learnt quite a bit - why not keep going?

However, the key question for me is whether you have, or can get access 
to, an oscilloscope of some sort. Do you? Without one the next stage 
will be all but impossible, because we need to check whether signals are 
present at various points in the circuit and they are signals that a DMM 
can't effectively see.

The scope really does not need to be anything special - I fixed a lot of 
synths using an ancient 10MHz Telequipment scope bought secondhand for 
£50 ($75). Most of the time we just need to see whether signal is 
present or not, and that it is roughly the right shape.

Let us know where you are at tool-wise and we'll see where to go next. 
In the meantime, what EXACTLY does the unit do? You say no sound, but do 
the selectors and panel LEDs work as expected?

Cheers,

Steve L.

Steve Lenham
Benden Sound Technology
www.bendensound.co.uk