Epiphone began producing amps in 1935 as part of their all-in-one Electar Hawaiian lap-steel set. The model in this month’s column is likely from the 1940s, but may have been part of a similar set.
Hello Ask Amp Man readers. I know I usually answer questions from you, but I’m once again going to stray from the status quo. I had this cool old Epiphone Electar 1x12 combo, probably from the late 1940s, come across my bench and I thought it would make a great column, so here you go.
The amp came to me as “not working.” Okay—that condition could have a plethora of potential causes, but let’s troubleshoot one logical step at a time. First, I check the fuse. Yes, it’s good, but it’s a 10-amp fuse, which I’m pretty sure doesn’t belong in what is probably a 10- to 15-watt amp. Just seeing this makes me think that the mains transformer may have been forced into expiration, but let’s not assume. I’ll put in a more appropriate fuse and keep moving.
Next, I’ll pull all the tubes. Prior to doing this, one should remember to make note of the position of each tube. Sure, sometimes you can refer to a tube chart either inside the amplifier or find a schematic and tube chart online, but for this amp neither of those niceties exist, so it’s time to make a little drawing. Now, with fuse in and tubes out, the next step is to bring up the amp slowly with the help of a Variac and monitor a couple key voltages. As the voltage is increased, both the filament and the AC high voltages are coming up, so it appears that the mains transformer is still functioning. At 120V input, the AC high voltage is in the expected range and the pilot light is on, so, hey, that’s a good sign, right?
The control panel was remarkably clean for its age, but replacing the capacitor associated with the tremolo control
was a smart pre-emptive improvement.
My next step is to power down, insert a rectifier, and bring the amp up slowly again, monitoring the DC high voltage. Since this amp utilizes a tube rectifier, I’m going to substitute a plug-in solid-state module, as the tube rectifier will not show any output until it reaches operating temperature—which will not happen with low line input voltages. Bringing up the line voltage, I see the B+ voltage coming up as well. I do this slowly over the course of hours to “re-form” the caps. Once I have it up to a few hundred volts DC, I’m confident that the filter capacitors, while maybe not optimal, are at least not shorted. I also did take some resistance readings on the primary and secondary side of the output transformer, and while this didn’t tell me the full story on the transformer, it did tell me that neither side is electrically open. At this point it appears that all the major components are in working condition, so now I’ll put the tubes back in and find out why there’s no output.
I look at my tube drawing, reinstall tubes, turn the amp on, the pilot light comes on, the fuse does not blow, I plug signal into the input jack, and turn up the volume control and … the customer is correct. No output. Okay, the first question I have about this amp is “Why does it have three 6V6 tubes?” Generally, 6V6s are used for output tubes and can occasionally be found as a reverb driver. This amp has no reverb, so what’s going on?
In looking at the circuit, I determined that the socket with the third 6V6 is the phase inverter, which drives the output tubes. Funny, I’ve never seen a 6V6 used as a phase inverter. Ever! This tube just doesn’t belong here. In looking at the wiring, I can see that it’s definitely not wired for a 6V6, but is wired for an octal tube much more suitable for a phase inverter: a 6SL7. I install a 6SL7, turn the amp on, and voilà, we have a tiny bit of sound. Progress!