I have to troubleshooota few input modules for my Yamaha PM2000, but
I'm a little lost on where to start. I have the sevice manual, and I
went through the wiring, and everything seems fine, sooooooooooo I'm
guessing the problems are tiher related to caps or the opamp(s). I
was hoping someone out tehre might be able to point me in the right
direction on what to check and how.

One of the modules dies while I was using it. The input just stopped
woring. I can very faitly hear it, if I crank the gain all the way,
but it's really fuzzy and ditorted.

The other three will only respond to very percussive high-spl signals.
Like hitting the 57 with my finger. other than that, I'm not
getting anything out of it. Any help would be greatly appreciated.
Thanks!

-Chris

In article ,
Chris wrote:
I have to troubleshooota few input modules for my Yamaha PM2000, but
I'm a little lost on where to start. I have the sevice manual, and I
went through the wiring, and everything seems fine, sooooooooooo I'm
guessing the problems are tiher related to caps or the opamp(s). I
was hoping someone out tehre might be able to point me in the right
direction on what to check and how.

One of the modules dies while I was using it. The input just stopped
woring. I can very faitly hear it, if I crank the gain all the way,
but it's really fuzzy and ditorted.

Put the signal into the mike input. Put the module on the extender.
Get out the schematic... check the signal level with a signal tracer
or a scope at the input of the first op-amp. Then go to the next one.
Then go on down the line. Eventually you will find the stage that is
the problem.

When you find that stage, check the coupling caps for leakage with an
ohmmeter, swap out the op-amp, poke around and make sure nothing is
oscillating, etc.

Your goal is to locate the stage where the signal stops, THEN start
seeing what went wrong at that stage.

The other three will only respond to very percussive high-spl signals.
Like hitting the 57 with my finger. other than that, I'm not
getting anything out of it. Any help would be greatly appreciated.
Thanks!

Both of these sound like bad coupling caps. Something is horribly out
of bias because DC is getting through a capacitor that is there to block
DC between stages. Find the stage and you'll find the cap. Or you can
shotgun out all of them if you prefer.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Both of these sound like bad coupling caps. Something is horribly out
of bias because DC is getting through a capacitor that is there to block
DC between stages. Find the stage and you'll find the cap. Or you can
shotgun out all of them if you prefer.
--scott

Thanks you very much, man. I really appreciate it. Can you suggest a
good supplier for caps and other such parts?

-Chris

In article ,
Chris wrote:
Both of these sound like bad coupling caps. Something is horribly out
of bias because DC is getting through a capacitor that is there to block
DC between stages. Find the stage and you'll find the cap. Or you can
shotgun out all of them if you prefer.

Thanks you very much, man. I really appreciate it. Can you suggest a
good supplier for caps and other such parts?

Depends. Digi-Key has the Panasonic FC caps, which are fine but only
available in radials. If you need axials you are a lot more limited.
Mouser electronics isn't bad either, and then the industrial places like
Allied and Newark, but I tend to go to Digi-Key first.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."