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Vintage Synth Repair

Index last updated: 2026-04-28 23:41 UTC

Message

RE: Re: Sequential Circuit Pro One UPD8021 chip

2013-09-10 by <babouche369@...>

Typically sounds like the capacitor used to init the chip has drifted. My guess is the INIT pin is not maintained at low-level long enough.



--- In vintagesynthrepair@yahoogroups.com, <vintagesynthrepair@yahoogroups.com> wrote:

I received the P8021 chip that I ordered from www.musictechnologiesgroup.com for the Sequential Pro One synthesizer and that seems to work.
The only small problem that I have is that the arpegiator stays ON most of the time. Sometime, when I turn OFF and ON the power, the arpegiator turns OFF and the synth behave normally.
I cleaned and checked the arpegiator switch but that's seems to be fine.
Anybody has seen this problem before?
Thank you!

Nicolas

--- In vintagesynthrepair@yahoogroups.com, Philip <eggwheatis@...> wrote:
>
> The original chip is custom programmed during manufacture. You'd have to find one that had actually been pulled working from a Pro-One..
>
> Basically impossible to find..that's why this guy developed a replacement and whilst doing it added new features.
>
>
> ________________________________
> From: Nicolas <nico678@...>
> To: vintagesynthrepair@yahoogroups.com
> Sent: Friday, 16 August 2013, 21:20
> Subject: [vintagesynthrepair] Re: Sequential Circuit Pro One UPD8021 chip
>
>
>
> Â
>
>
> Hi,
>
> I sent him a message and I think it's the same guy. He's on vacation too.
> The price is 120$ + shipping which seems a little bit high to me.
>
> I'd like to find the original chip if it's still possible.
> The number written on the chip is D8021C and it was made by NEC.
>
> Thank you!
>
> Nicolas
>
> --- In vintagesynthrepair@yahoogroups.com, "grantpbt" <grantbt@> wrote:
> >
> > The seller is on vacation, but more info here: www.musictechnologiesgroup.com
> >
> > GB
> >
>

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