This is my 1967 Blackface Fender Bassman. It is a CBS amplifier, built shortly after Leo sold the company but before they started making changes that changed the quality tone Leo was famous for. You can tell a big difference in the layout from a Silverface amp. Cloth coated wire, neat layout, better quality parts, things like that.
This amp wasn't quite well when I first got it. A short while after buying it, I noticed it hummed really bad. Ok, replace the filter caps and other electrolytics. Still hummed. A service tech figured out it was the power transformer. I didn't play it much, I usually used the Silverface Bassmans. When I bought my Leslie 16, I got this amp out to power it. It started acting weird again, cutting in and out. I replaced tubes, caps, checked resistors, and couldn't figure it out. This time I took it to Jeff Andrews of Andrews Amp Lab, and at first he thought it was the power tube sockets, and after replacing them, it still had problems. Jeff then pinned it down; it was the choke.
Now the amp is sounding great. It has new JJ 12AX7s and SED (The REAL Svetlana) power tubes. I rebuilt the Bass channel to mimic the Silver Face Super Reverb, with a .022 instead of the normal .047 cap. I like it a lot, it gives a bit more mids.
Mods and upgrades:
New Power tranny.
New Power tube sockets.
Replace all electrolytic caps.
Replaced various resistors out of spec.
Replaced phase inverter coupling caps with Orange drops.
Removed Death Cap and replaced AC cord with grounded cord.