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Valley 401 schematic

Posted: Wed Jun 26, 2019 2:48 am
by ChuckG
I need one...

Seems to have DC on the preamp input. Level pot is scratchy, Overload lights come on when you adjust the control with no audio input applied.
Tried disconnecting the 48V phantom source, no change.
The +/- 15V supplies are clean.
Checked the surface mount caps for shorts, found none.

Anyone have a drawing for one of these?

Re: Valley 401 schematic

Posted: Wed Jun 26, 2019 12:05 pm
by Bill DeFelice
I had a scan of the manual but can't find it at the moment. Perhaps the 400 schematic would be close enough to help in troubleshooting:

Valley Audio 400 Manual PDF

Valley Audio 400 schematics only link (secondary)

edited: corrected typo

Re: Valley 401 schematic

Posted: Wed Jun 26, 2019 3:04 pm
by ChuckG
Thanks Bill!
Unfortunately the 401 and 400 have different input sections.

They had the drawings included in the 400 manual but removed them for the 401.
Why do manufacturers do that lol. Really annoying.

Re: Valley 401 schematic

Posted: Thu Jun 27, 2019 6:30 am
by Bill DeFelice
Reminds me of the Aphex 320a Compellor manual which the first version had schematics and they pulled them with every revision afterwards.

Hopefully someone will happen across the schematic for the 401 for you, Chuck.

Re: Valley 401 schematic

Posted: Mon Jul 08, 2019 10:43 pm
by ChuckG
No longer needed...I did manage to get this fixed. SSM preamp chip was putting DC on the output bus at higher gain levels.
They are no longer available, but Ebay has plenty.
Unfortunately I could not fix the second unit as someone had "fixed" it before me, ruining the SMD mounting pads.