I fixed the foot switch for my Quad!!

Bottle Rocket, V-1, V-twin.
Footcontrollers, midi switchers, amp switchers and Mesa Boogie products not covered.

Moderators: Guitarzan, Grandor, ned

Post Reply
Bottle Rocket
Posts: 4
Joined: Sun Mar 14, 2021 5:45 am
Location: Midwest, United States

I fixed the foot switch for my Quad!!

Post by 16Bit » Fri Apr 02, 2021 6:36 pm

I wanted to post this to try to help anyone who is having a similar problem with their Quad Preamp.

I found an FU-2 foot switch on an online auction site, and when I got it home I noticed that it had a similar problem that a lot of other people have had; when a button was pressed, all the LEDs on the preamp and the foot switch itself lit up at the same time and the channels wouldn’t change.

I traced the problem down to a faulty 74165 chip and a broken leg on one of the big disc capacitors. I found replacement IC chips on eBay, and when I popped the new one in, it worked like a champ. I also gained a little bit of insight on the signal path from studying the not-so-great schematic and doing some voltage measurements on my own. If anyone has questions, feel free to ask!

User avatar
Bottle Rocket
Posts: 12
Joined: Fri Jun 29, 2007 4:28 pm
Location: California - LA/Orange

Re: I fixed the foot switch for my Quad!!

Post by HighWattGuitars » Sun Apr 04, 2021 11:47 pm

Thanks. I have a couple of those. I might refer back to this if I should ever incur such trouble. By the way- There once was a time when I yanked the cable from a Quad footswitch to effect an emergency repair on the footswitch of a MkIV.
MkIII black
MkIII purple
MkIII red
MkIII blue
MkIVa (2nd of 2)
Quad (with FU-2)
Quad (with FU-2A)
50 Caliber (EL84)
Mk series 4x12 (4 cabs)
High Gain Amp Switcher
MkIIa Series 300 Imbuya
MkIVa (1st of 2)
MkIII Coliseum

Post Reply