[sdiy] SH-101 help

[Rob B]

I don't know why you ppl all say that "opamps can't fail"..

I have seen *many* flagged opamps parts that are known for deteriorating
CMRR.. Sequential gear is riddled with them, as are some Roland units. I
have an 808 that I just fixed... The input resistance seemed to just to go
crud over the period of a week.

I guess many of you build rather than repair, in which case the parts you
are working with don't have as much mileage.. This stuff *will* eventually
fail, and, some of it being 20+ years old, its starting to happen in a big
way..

I have even had to throw out a lot of modern-day opamps because they were
bad in mass produced designs, that, when tested, didn't meet the minimum
ratings.. This issue is getting worse in the bad economy, where every part
counts and they are looking to squeeze out every last bit of profit and
nearly every lot gets shipped no matter what due to the huge demand and
tight margins.

So far, my list of offenders, in order of occurence

1) Connectors, pots, electromechanicals
2) caps
3) opamps, esp TL series. Seen this in S&Hs in the p5s, in 808s, the Arp
Odyssey filter board, and the SH101
4) VCA/Buffer amps burned up after being left railing and overheating due to
a bad cap. ;)
5) Occasionally a DAC goes bad, or more specifically the internal output
buffer for the dac.

Rob


----- Original Message -----
From: <ElmacacoX at aol.com>
To: <patchell at silcom.com>; <synth-diy at dropmix.xs4all.nl>
Sent: Tuesday, January 29, 2002 12:09 AM
Subject: Re: [sdiy] SH-101 help


> I've had 2 dual opamps fail in roland gear of about the same vintage,
> cr-8000 and
> sh-2,  aparently roland op amps are kinda weak... and I don;t have much
> roland gear and haven't seen alot of it either.
>
> on both I thought it couldn;t be that simple...
>
> hopefully for you it is.
>
> Good luck
>
> Eduardo
>