[sdiy] Power supply and FETS

[Rob B]

Hrm.. I have a similiar problem with an SH5 right now.. Whenever the
powersupply is hooked into the bender board, the -15 rail runs up to
+7volts! In all my years, I have never seen this. The +15volt rail doesn't
even flinch when this happens.

I did a load test on the -15volt rail by putting a 200k resistor between it
and ground, and it doesn't droop at all. The resistor gets pretty warm, so
that made me feel good at least that it can supply a good deal of current.

Changed all the opamps thinking one of them had an input burned short, but
no luck.

Most of the caps are of the film variety, so I wouldn't think they would be
having any problems yet.

One of the most strange episodes I have ever seen.. Worst part about it is
that I had *just* finished fixing it and getting it running! I played with
it for a few days, and it just stopped working again. One of the more
unusual things I have seen happen.

aim : cybrgzr0 <--last thing is a number

----- Original Message -----
From: RichR <rrowley at btinternet.com>
To: <synth-diy at dropmix.xs4all.nl>
Sent: Tuesday, August 14, 2001 8:03 AM
Subject: [sdiy] Power supply and FETS


> Hi all
> A few questions for my first post.
> I've built a few modules that require a +12v -9v power supply however the
> rest of my modules run at +12v -12v as does my power supply.I've tried
using
> a resistor to drop the -12v to -9v but it reads as +9v when I do this.Is
it
> a case of using different value resistors from the -9v rail?If so how do
you
> calculate the correct values to use?Is there something I'm missing?
>
> How do you measure the Vp of a J fet?
>
> Thanks
> Rich
>