TheHammer1982
Well-known member
So, you know how most sane people start off with something like a 5E1 Champ as their first amp project? Yeah, that wasn’t what I did lol.
Back in 2006 I purchased a B52 AT212 100W combo amp from Guitar Center for $750. It had two gain channels (that share the same EQ), a mid-sweep contour control that could be used with both of the gain channels, a fantastic clean channel, and a decent reverb tank.
I used it for a number of years off and on without much of an issue. Unfortunately life got in the way and it ended up in storage until about 5 years ago. It worked great for about a year and then started developing issues with the volume dropping off and then finally it became unplayable. At the time I didn’t know very much about tube amps other than how to replace the tubes and set the bias. I found the schematic and was quickly overwhelmed by what looked like pieces of spaghetti thrown on the wall with strange symbols and numbers added in for good measure.
At that time I decided that the best thing to do was buy another amp, which I did. I bought an Orange Rocker 15 Combo and then a Wampler Pinnacle Deluxe (my first pedal). Up until that point I had only used my AT212’s distortion and reverb.
After I got the Pinnacle Deluxe I became hooked on wanting to try more pedals and became interested in building my own. I started learning more about schematics and it wasn’t long before I could understand what all of the symbols and values meant. It was at that point that I decided it was time to take on the AT212 and see if I could figure out what was wrong.
The first thing I did was start checking the tubes and found a bad 6L6 power tube and a couple of ECC83 preamp tubes. I ordered an Apex matched quad of JJ 6L6s and 4 JJ ECC83s for the preamp section. Unfortunately this did not solve my issues. The next step was to pull the chassis out and start inspecting components on the board. Right off the bat I noticed some swollen caps on the power section and a discolored plug. I also noticed that the bridge rectifier was mounted flat on the board and touching C84 and R121. This amp was supposedly designed by Bruce Egnater for B52 and manufactured in China so maybe something got lost in translation.
I replaced all of the caps, both cement resistors, and added some legs to the bridge rectifier to get it up off the board. The burnt plug was actually still good so I left it (primarily because I forgot to order a new one lol).
With all of that done I STILL had an issue with the volume dropping while playing. For shits and giggles I started testing all of the control pots on the amp and found several that were malfunctioning, one of which was a volume pot for the OD section. “Ah ha!” I thought to myself. “This has to be it!”. After replacing all of the pots on the front panel the volume issue appeared to be solved, for about 5 minutes, when the volume started dropping again. This time it was different though as the volume loss wasn’t as extreme as before. The issue was only affecting the OD section as the clean channel was working fine. At this point I focused my attention on the preamp tube sockets and noticed that two of them were quite loose. I decided to replace all 7 of the 9-pin sockets with Belton brand sockets since I had the amp apart and it was only $20. STILL the volume issue persisted but I wasn’t giving up. I would bet money that I had ~60 hours into this amp (including all of the research I did to learn the theory of operation and how to read schematics) and was determined to see it through. After going over the board again I noticed two capacitors that hadn’t been replaced yet.
Thankfully the trace was on the underside of the board and wasn’t damaged. After cleaning that up and replacing the caps the amp is working 100% and sounds better than it did new. I’ve played it for ~4 hours so far without a single issue. The last thing I have planned for it is to replace the Tolex and grill cloth.
Back in 2006 I purchased a B52 AT212 100W combo amp from Guitar Center for $750. It had two gain channels (that share the same EQ), a mid-sweep contour control that could be used with both of the gain channels, a fantastic clean channel, and a decent reverb tank.
I used it for a number of years off and on without much of an issue. Unfortunately life got in the way and it ended up in storage until about 5 years ago. It worked great for about a year and then started developing issues with the volume dropping off and then finally it became unplayable. At the time I didn’t know very much about tube amps other than how to replace the tubes and set the bias. I found the schematic and was quickly overwhelmed by what looked like pieces of spaghetti thrown on the wall with strange symbols and numbers added in for good measure.
At that time I decided that the best thing to do was buy another amp, which I did. I bought an Orange Rocker 15 Combo and then a Wampler Pinnacle Deluxe (my first pedal). Up until that point I had only used my AT212’s distortion and reverb.
After I got the Pinnacle Deluxe I became hooked on wanting to try more pedals and became interested in building my own. I started learning more about schematics and it wasn’t long before I could understand what all of the symbols and values meant. It was at that point that I decided it was time to take on the AT212 and see if I could figure out what was wrong.
The first thing I did was start checking the tubes and found a bad 6L6 power tube and a couple of ECC83 preamp tubes. I ordered an Apex matched quad of JJ 6L6s and 4 JJ ECC83s for the preamp section. Unfortunately this did not solve my issues. The next step was to pull the chassis out and start inspecting components on the board. Right off the bat I noticed some swollen caps on the power section and a discolored plug. I also noticed that the bridge rectifier was mounted flat on the board and touching C84 and R121. This amp was supposedly designed by Bruce Egnater for B52 and manufactured in China so maybe something got lost in translation.
I replaced all of the caps, both cement resistors, and added some legs to the bridge rectifier to get it up off the board. The burnt plug was actually still good so I left it (primarily because I forgot to order a new one lol).
With all of that done I STILL had an issue with the volume dropping while playing. For shits and giggles I started testing all of the control pots on the amp and found several that were malfunctioning, one of which was a volume pot for the OD section. “Ah ha!” I thought to myself. “This has to be it!”. After replacing all of the pots on the front panel the volume issue appeared to be solved, for about 5 minutes, when the volume started dropping again. This time it was different though as the volume loss wasn’t as extreme as before. The issue was only affecting the OD section as the clean channel was working fine. At this point I focused my attention on the preamp tube sockets and noticed that two of them were quite loose. I decided to replace all 7 of the 9-pin sockets with Belton brand sockets since I had the amp apart and it was only $20. STILL the volume issue persisted but I wasn’t giving up. I would bet money that I had ~60 hours into this amp (including all of the research I did to learn the theory of operation and how to read schematics) and was determined to see it through. After going over the board again I noticed two capacitors that hadn’t been replaced yet.
Thankfully the trace was on the underside of the board and wasn’t damaged. After cleaning that up and replacing the caps the amp is working 100% and sounds better than it did new. I’ve played it for ~4 hours so far without a single issue. The last thing I have planned for it is to replace the Tolex and grill cloth.
