1972 Fender Bandmaster Reverb

[xtian]

This amp was covered in sh*t and hidden in a barn. I applied a LOT of elbow grease, and got her cleaned up. Added a pair of 8" Jensen C8R speakers to the head cabinet to make a mini combo.

Amp was working well as it came, but e-caps were beginning to crack and bulge, so replaced them all. Posting now because wondering if anyone else has seen such a strange dog house. One of the 20uF caps had a cardboard jacket with the polarity marked incorrectly. And the dropping resistors following the choke were 2K2, 10K, instead of 1K, 4K7, as seen on many similar schematics of the era.

[mort]

I'm still a learner so take with a grain of salt, but my comments are as follows...

The filter caps in a doghouse are often positioned differently from one another, if you follow the paths closely it should match the schematic though. I can see more than one are positioned opposite in your photo. Is this what you were talking about as backwards, or was one of them actually labelled incorrectly?

And the resistor value differences will only result in a slightly higher B+ on those nodes and on down the line. Perhaps it was done intentionally or maybe that's just what was on hand that day.


Otherwise a good looking amp. I can only imagine how much low end will be lost through those speakers though.

[xtian]

The middle of those five caps is installed correctly, but mislabeled. It lasted 44 years, and still sounded decent, with no hum!

[sgelectric]

Just wondering whether the reverb pan is affected by its close proximity to the back wave of the 2-8" speakers?
Any issues at volume?

SG

[xtian]

The reverb pan is originally attached to the front valence, and must be moved to the floor of the cabinet to accommodate the speakers. So I was wary about the performance of the reverb afterward, and the potential for increased EM hum from the PT. No worries--works and sounds great, no added hum.

"At volume" is a reasonable question about the Jensen C8R, but again, no worries, because the speakers don't stand up to much--they begin to sound flappy and flubby above 5 on the Volume control.

[52 Bill]

Neat idea. It reminds me of the old Rickenbacker Transonic head that had a small speaker in the head cabinet. It was supposed to let you use it as a practice amp.

It probably took less than 10 minutes for the speaker to be blown by using it that way.

[xtian]

I'm not the first to do this mod. This fellow made a nice demo:

[drewl]

Ha, I was going to do that to a Marshall JCM 800 2210 I had years ago!

Throw a couple 5x7's or similar small speakers for home jamming!

Luckily I didn't.