16Bit
Member
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!
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!