Vintage Synth Repair

PS:

Also having a cap in the C46 position seems to do nothing..ie it
sounds the same whether the caps in place or not. 


--- In vintagesynthrepair@yahoogroups.com, Philip <eggwheatis@...> wrote:
>
> Hi guys..bought a supposedly fully working 606 of off
> eBay to find it has problems...
> 
> 1. It wouldn't work with an AC adaptor, batteries
> only. Anyway I fixed that, was some shorted caps and a
> bad regulator. It had some battery damage too around
> that area.
> 
> Next job..the Hi-hats and cymbal sounded really weird,
> kind of flutey and going up and down very slowly in
> pitch. Scoped it and found a bad 4558...fixed? Well
> sort of, the cymbal sounds fine, the hi-hat sounds ok
> except that the open hi-hat sounds identical to the
> closed hi-hat i.e. not open with a long decay. 
> 
> All the transistors in the hi-hat circuit check out
> fine. I've changed the 2904 op amp, the oscillator IC
> is fine (4584). The trigger is fine from the CPU...
> The tempo clock signal is ok as well to the Hi-hats. I
> thought maybe the closed hi hat trigger was triggering
> the open too or something. 
> 
> So I moved to caps. I've changed every single
> Electrolytic marked in the hi-hats section. No change.
> I notice one thing. If I change the value of cap C45 I
> can make the open hi-hat decay longer but I'm moving
> it well away from the stated 1uf it's supposed to be.
> 
> One other thing; when you start a pattern off the
> first hi hat beat is raised in pitch also when you
> switch between write mode or play mode, the pitch of
> all the cymbals, hi-hats change. You get a higher
> pitch in play mode.
> 
> So to recap I basically have an open hi-hat that
> sounds identical to the closed hi-hat. And some weird
> pitch change stuff going on.
> 
> Im looking at it again tonight so if anyone has any
> ideas, shoot.
> 
> Thanks, Phil.
> 
> 
> 
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