API 554 in/out switch - question

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QUEEF BAG

Well-known member
Joined
Jun 12, 2009
Messages
563
Location
Seattle
i have a 554 on the bench, high and low bands are active
no matter what  position the in out switch is in.
mid band behaves as it should.

it's gonna be some physical issue, and i'm not to concerned, but...

looking at the schemo trying to track this down, i can't see the in out switch
being much of anything, except sort of an led on off.

i know API schematics are a pain, but this looks like it wouldn't do anything.

wtf?

 

Attachments

  • API 554.pdf
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The switch also provides a pull down to -16v to switch the FETs on the output of the filters. Look to see if U4 and U9 are switching correctly.
 
doh!

thanks!   i'll rig up a jig and check it out

gonna hafta look at the schemos with this in mind.
never thought about  'logic'  in an api eq before.

i thought it was just straight switching.
 
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