EddyLenz
Well-known member
Hi Guys,
I recently got this old Plexi for restoration. It arrived in non-working condition and looking inside, I wasn't surprised.
It looked like it was probably modded in the 80s or 90s. All the mustard caps were replaced with WIMA style caps in a really bad way. It had a one wire mod with completely wrong component values and a standard 2203 style master volume that was added on the front. The amp needed a full recap and new tubes.
While I was doing the recap, I noticed a very weird issue. On that day, I didn't have any 10uF in stock for the bias circuit, so I left the original ones to test it. With those original bias caps, the amp was behaving very weirdly. It had tons of ghosting and added harmonics that were as loud as the real signal. I knew that sounded like bad filter caps, but I didn't immediately think about the bias caps. Once I ruled out everything else and measured them, I found that both of them were completely dead...
Having replaced the bias filter caps a few days later, the amp worked perfectly. It's just one of those holy grail guitar sounds that's really fun to play.
Here's what it sounds like with my 1991 Greenback cab.
and here it is with my stereo rack IR setup
I recently got this old Plexi for restoration. It arrived in non-working condition and looking inside, I wasn't surprised.
It looked like it was probably modded in the 80s or 90s. All the mustard caps were replaced with WIMA style caps in a really bad way. It had a one wire mod with completely wrong component values and a standard 2203 style master volume that was added on the front. The amp needed a full recap and new tubes.
While I was doing the recap, I noticed a very weird issue. On that day, I didn't have any 10uF in stock for the bias circuit, so I left the original ones to test it. With those original bias caps, the amp was behaving very weirdly. It had tons of ghosting and added harmonics that were as loud as the real signal. I knew that sounded like bad filter caps, but I didn't immediately think about the bias caps. Once I ruled out everything else and measured them, I found that both of them were completely dead...
Having replaced the bias filter caps a few days later, the amp worked perfectly. It's just one of those holy grail guitar sounds that's really fun to play.
Here's what it sounds like with my 1991 Greenback cab.
and here it is with my stereo rack IR setup
