Ampeg SVT 3 Pro in the lab
Compared to Ampeg SVT III which has old school TO-3 package MJ15022/MJ15023 transistors the SVT 3 Pro has switched to a MOSFET output section with an IRFP9240/IRFP240 combo. Same as Ampeg SVT 4. Ampeg B2R also has a very similar output section. A lot of these 90s Ampeg SS output sections are similar, just bigger or smaller depending on the power handing of the amp, usually MOSFETS. This one was cutting out from broken solder connections.
Schematic for Ampeg SVT 3 Pro — https://drive.google.com/folderview?id=0B01EXvY0__YYU0kySjZwOERxeDA&usp=sharing