bubbi

Pultec problem
« on: February 13, 2018, 10:12:30 AM »
Hi all,
a while ago I build two Pultecs (EQP-1A) and am pretty sure they worked like they should to begin with.
However now, when Lo-boost is at 0 it is still boosting about 5db and the boost follows the lo-freq switch. If I turn up the boost knob I get more boost so the only problem is that I can't get to zero boost. Everything else works normally and if I bypass the boost goes away.

Any ideas?


scott2000

Re: Pultec problem
« Reply #1 on: February 13, 2018, 11:07:07 AM »
Both are acting the same way?????

Maybe a pot or component somewhere in that circuit is out of tolerance?????

ruffrecords

Re: Pultec problem
« Reply #2 on: February 13, 2018, 11:18:12 AM »
The bass boost pot shorts out the boosting caps when turned to zero. If you still get boost at zero then my first suspect would be this pot.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

JohnRoberts

Re: Pultec problem
« Reply #3 on: February 13, 2018, 11:21:49 AM »
Or check solder connections.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...

bubbi

Re: Pultec problem
« Reply #4 on: February 13, 2018, 12:31:24 PM »
Ok found that if I lift the pot just a tiny bit above zero the boost reduces to around 1.5db instead of 5db so seems like pot is shorting at zero. However still this 1.5 db boost... should maybe try swapping out the pot....

ruffrecords

Re: Pultec problem
« Reply #5 on: February 13, 2018, 01:28:02 PM »
Ok found that if I lift the pot just a tiny bit above zero the boost reduces to around 1.5db instead of 5db so seems like pot is shorting at zero. However still this 1.5 db boost... should maybe try swapping out the pot....

Definitely sounds like a dodgy pot.

Cheers

Ian
www.customtubeconsoles.com
https://mark3vtm.blogspot.co.uk/
www.eztubemixer.blogspot.co.uk


'The only people not making mistakes are the people doing nothing'

JohnRoberts

Re: Pultec problem
« Reply #6 on: February 14, 2018, 11:57:56 AM »
I have seen pots with cracked phenolic substrate so would work up to the crack, then go open.  But check solder joints too.

JR
John Roberts
http://circularscience.com
Tune it, or don't play it...