MOTM

Finished putting together a 110 late last evening (maybe that's the 
problem).  

The RingMod part works fine.  I can use the X & Y in and get audio at 
out at about the same level as it goes in.  

My problem seems to be with the VCA section.  I plug audio in but 
only get faint audio out (with the Gain all the way up).  It is 
working but seems to greatly attenuate the source - if I turn the 
mixer way up and sweep the gain on the VCA counterclockwise I can 
hear it's effect.

Don't know if this is good/bad/otherwise but if I touch the very tip 
of a cord to either out on the 110 I pick up a radio station - I 
don't know if that means something isn't grounded correctly (???)

I've checked all the polarity sensitive components and all are in the 
right orientation.

I've checked the resistors and most of the caps several times and 
everything is OK there.  Haven't triple checked the axial caps 
(printing is really small so I thought I'd get a magnifying glass to 
verify) but I'm pretty sure they're correct.

I'm going to double check for obvious shorts but checked several 
times during construction and feel fairly confident about that.

Any ideas?

Thanks,

John

PS - the CEM chip doesn't sit absolutely flat on the socket should 
it?  I had to pinch the legs in to get it to fit in the socket and 
it's slightly raised (but inserted all the way in to where the legs 
flair out).

> My problem seems to be with the VCA section.  I plug audio in but
> only get faint audio out (with the Gain all the way up).  It is
> working but seems to greatly attenuate the source - if I turn the
> mixer way up and sweep the gain on the VCA counterclockwise I can
> hear it's effect.

i had the opposite problem when i built mine: the ring mod woudln't work.
after much head scratching and circuitboard-peering, i noticed the 3330
was sort of off kilter. i reseated it and ring modulated crap all through
the night... another feather in the cap of the "sockets suck" argument.

> Don't know if this is good/bad/otherwise but if I touch the very tip
> of a cord to either out on the 110 I pick up a radio station - I

ooh. can't help you there...

> PS - the CEM chip doesn't sit absolutely flat on the socket should
> it?  I had to pinch the legs in to get it to fit in the socket and
> it's slightly raised (but inserted all the way in to where the legs
> flair out).

oh... i didn't see that. this is probably definitely your problem.

bleep(probably definitely).
out.

So should the CEM chip sit absolutely flat on the socket?  

Mine sticks up by maybe 1/2-3/4 the thickness of a dime.  Anybody else have
to bend the legs in a little bit to get it in.  W/O doing that there was
absolutely no way it was going in by itself.

Thanks,

JP

-----Original Message-----
From: bleeped [mailto:bleep@...]
Sent: Wednesday, July 25, 2001 3:31 PM
To: jpotter@...
Cc: motm@yahoogroups.com
Subject: Re: [motm] 110 VCA/RM Troubleshooting



> My problem seems to be with the VCA section.  I plug audio in but
> only get faint audio out (with the Gain all the way up).  It is
> working but seems to greatly attenuate the source - if I turn the
> mixer way up and sweep the gain on the VCA counterclockwise I can
> hear it's effect.

i had the opposite problem when i built mine: the ring mod woudln't work.
after much head scratching and circuitboard-peering, i noticed the 3330
was sort of off kilter. i reseated it and ring modulated crap all through
the night... another feather in the cap of the "sockets suck" argument.

> Don't know if this is good/bad/otherwise but if I touch the very tip
> of a cord to either out on the 110 I pick up a radio station - I

ooh. can't help you there...

> PS - the CEM chip doesn't sit absolutely flat on the socket should
> it?  I had to pinch the legs in to get it to fit in the socket and
> it's slightly raised (but inserted all the way in to where the legs
> flair out).

oh... i didn't see that. this is probably definitely your problem.

bleep(probably definitely).
out.

> So should the CEM chip sit absolutely flat on the socket?

i can't recall how far above the socket the bottom of the chip is, if any
at all. my problem was that the chip was in all the way on one side, but
not the other. it was seated crooked. bending the legs is fine, i think,
as long as they make full contact with the socket. try to work the chip in
a little farther by alternately pressing on each of the ends of the chip.

i hope this helps!

bleep.
out.

<jpotter@...> wrote:


> PS - the CEM chip doesn't sit absolutely flat on the socket should
> it?  I had to pinch the legs in to get it to fit in the socket and
> it's slightly raised (but inserted all the way in to where the legs
> flair out).

I believe the chip should go most of the way in - in any case it should sit
evenly all around.  It's a very tight socket, and it's really easy to fold a
leg and *not* notice it.  I've had consistently good results by using a chip
insertion tool that has a grounding lug for safety.  It forms the legs
nicely and also allows for more evenly distributed insertion force.  I
actually use this tool for all 8/14/16-pin ICs regardless if they're going
into a socket or not.  Luckily, I haven't needed a puller yet.  Thanks go to
Paul for not socketing most of the chips!

Cheers,
George

Reseated the CEM chip and everything is A-OK.

Thanks everyone.

JP