This is another of Fred Shuman's amps. He got this Gibson BR-6 under mysterious circumstances, and it was never plugged in because the cord was so ratty. Alarmingly ratty.
This is the "Style 2" Gibson BR-6 - it has a horizontally longer cabinet than the "Style 1", which looked a lot like an old radio from the 1930s. In 1955, the BR-6 was replaced by the GA-6.
The BR-6 has a single volume control, two instrument inputs, a fuse and an on-off switch. No pilot light, that was available on the higher-priced amps. The preamp uses a twin triode 6SL7, and the phase inverter is a 6SN7. Two 6V6 output tubes, and a 5Y3 rectifier. Output was specified at 8 to 10 Watts. Price when new was $77.50.
I'm sure it's fine - just plug it in.
The chassis is wired point-to-point in a fairly simple layout.
All the components in this amp were either bad or wrong. OK, maybe I'm exaggerating a bit. All the caps were bad, the electrolytics and the wax tubulars. The volume pot was bad. The power cord was frightening. The tubes were in good shape except for the 6SN7, which was dead.
Probably decades ago, the volume pot quit working, so somebody wired the inputs directly to the preamp tube. Meh.
The 10" field coil speaker is a Rola, dated 1950. Field coil speakers are notoriously inefficient, and were rapidly being replaced by permanent magnet speakers even as this amp was manufactured.
One good thing you can say about field coil speakers, though - they came with a "free" choke for the B+ power supply. Ha.
I replaced the horrifying power cord with a modern 3-conductor cord, and wired the fuse and switch to the line leg only. I replaced the filter capacitors with modern equivalents. I replaced the coupling caps with orange drops. Installed a new 500K volume potentiometer. I rewired the grounding scheme a bit to reduce potential hum.
I replaced the 6SN7 tube with a good one from my Secret Stash. I checked voltages before installing the tubes, and everything seemed to be OK.
The amp started OK, no funny noises. I played my pretend 1954 Stratocaster through it for a while. I t sounds fine. It's not loud. I played it on "10" most of the time - not much distortion, which is what the amp was designed to do. It's a nice little amp. A Gibson BR-6 lap steel would sound great through it, I bet.