cheers, Sjoerd
At 23:22 21-3-02 +0000, you wrote:
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----- Original Message -----
From: "David Joeright" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, March 04, 2002 11:08 PM
Subject: Re: [TB-303.org]
> from TB-303 resources mailing list
> -------[ http://www.tb-303.org ] ----------------------
>
> The only way to replace the CPU is to get it from another 303, or someone
> who has an extra or collects the parts. Sometimes you can get broken 303s
> for a good price, but they seem to be scarce these days. Just out of
> curiosity how did you determine it was the CPU, did you take it in for
> service ?? Or did you determine this yourself ?, if so how did you test
it
> ??
> --
>
It's important to be absolutely sure that the CPU is at fault. I've had
several 303's to repair which previous so-called 'techs' have blamed the
fault on the CPU, only to find that it was in fact one or more of the three
memory IC's that were in need of replacement. A faulty memory often causes
bizarre effects which can quite easily be blamed on the CPU.
Power supply faults shouldn't be ruled out either - an undervoltage or
significantly noisy power supply to the digital section will cause trouble.
You see lots of Roland gear with slightly buggered power supply circuits
usually because someone's used a wallwart of an incorrect voltage at some
point. Relatively unlikely but nevertheless a possibility.
I've actually got one or two original TB303 CPUs which were the last I was
able to get from Roland some time ago. Never had to use one yet. Faults have
almost always been attributed to one of the above in my experience.
Trev
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