This is my 1976 Bassman 100. It is a 100 watt amp, and you would think it would simply be a larger version of the 50 watt Bassman tops of the 60's and 70's. That's not the case, however. The 50 watt tops had an extra tube mixing stage between the preamp and the power amp, and the 100 does not. It's really a simple amp. The power transformer looks to be the same as used in the 100 watt Twin Reverb, but the output transformer is noticeably bigger.
The 70's Fender circuitry wasn't all that great for guitar, so I rebuilt the amp to resemble the 60's AB763 Fender Blackface circuit. The amp now is basically a Super Reverb in one channel, and a Twin/Showman in the other, of course neither have reverb or tremolo. I disconnected the crappy master volume, and used the pot to institute a mod called the "Resonance control" which essentially is a variable negative feedback control. It seems pretty cool in that on one end of the pot you get a lot of distortion and crunch and on the other end, you get uber clean and spank.
Since the mods this thing is a rock machine!! Great cleans, and great overdrive. It sounds great through my 4x12. Of course, it's quite loud, but an attenuator helps cut down the blast to a manageable level. I put some NOS preamp tubes in it, and tried out the long bottle TAD 6L6 power tubes, they sound great. Click on the pics below to see the changes I made.
The condition of the amp was pretty poor when I got the amp. The cab and faceplate had seen better days. It looked like the amp was dropped or rammed into something at some point. The cab was cracked open on one end and I took it to my friend Danny for repair. The chassis was bent in and I had to buy some pressure clamps to straighten it out. Both transformers were loose, and the output transformer was bent towards the cracked side. I had to undo the bolts holding it in and bend the tabs straight again. Once the cab and chassis were fixed, I bought new tolex and hardware and re-Tolexed the cabinet. It turned out pretty good! The picture above is after the re-Tolex, the picture below is before. The faceplate was quite scratched up but there was not much I could do about that.
Also below are some before/after shots of the internals of the amp mods. Click on the pictures for a larger view.