[sdiy] Re: Help! Fatman problems!

[Scott Gravenhorst]

John Goodall <jgoodall at rm.com> wrote:
>Hi everyone,
>
>I've just plugged in my Paia Fatman having finished construction of it to
>discover it doesn't work :0(
>(It was to be expected really, it's the 1st synth I've built)
>
>Here's the problem. When I strike a key I get a very short noise coming out
>but it's very brief and to my electronically untrained ear sounds like it
>could be a really low bass note, maybe just 1 cycle of the waveform(?).
>
>Playing a higher or lower note on the keyboard makes no noticeable
>difference to the pitch, neither does changing any of the 5 trimmer
>resistors or the pitch control on the front.
>
>The 1800 ohm resistor that bridges R34(1) & R34(3) was missing from the kit
>so I ordered one from RS, it's the same value but states it is 1% (R5%).
>I've also used a blue led for the power light, I know these use slightly
>more current but that couldn't be the problem could it..?

I would doubt that it draws so much power as to cause a problem.
That brings me to the first of my own trouble shooting techniques:
First measure the +5, +8 and -12 volt supplies.  If you
have a scope, look at them with the scope.  On DC make sure
they are a flat line.  On AC, keep turning up the scope's 
sensitivity until you see some noise or ripple and measure that.
If you don't have a scope, you can still measure noise/ripple
with a DVM set to AC, again, turn up the sensitivity until you
can get some numbers.

Let us/me know what you see.  I need to know if your
supplies are right before we can go any further.

>Please can someone help me? It would be great if you could advise me in
>simple terms, I am a total novice!

(c:  We *all* start there.

>
>Many thanks, John
>
>
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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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