Gibson EH-150 amplifier questions

[Murray Leshner]

Hello:

1) Any idea who provided Gibson with the 12" electrodynamic (field coil) Ultrasonic Reproducer speakers? I saw 12F2 ink-stamped on one in a photo recently...maybe here. I don't assume 12 and a letter or two mean Jensen. I used to, but have found speakers that were and were not that had that style of marking but not found in any old catalog scans.

2) I am looking for a Gibson-drawn EH-150 type/style 3 schematic (6F5-6C5-6C5-6C5-6L6-6L6-5U4G with interstage transformer phase inverter). I have only seen an owner-drawn one that has two details I don't trust. It was supposedly in the manual, but I find Gibson manuals harder to find than schematics (which usually do not match the chassis you happen to have. I don't like free spirit improvisation in that context).

Thank you

[Dave Grafe]

You probably have all this information but for others who are new to this sweet amp here is a beginning place...
https://www.tdpri.com/threads/gibson-eh-amps.313169/

As for the speaker that is a big OOF!! for restoration projects. Up until the mid-1950's it was common to use an active speaker coil winding to double as a power supply choke while supplementing or replacing a permanent magnet. Your best bet may be to find a good speaker tech to help you repair the old one as these haven't been manufactured by anyone for many decades. Maybe check in with forum member and ace speaker reconer Jeffrey Maxwell, if he can't help he may be able to point you in a helpful direction.

[John Dahms]

My foggy memory tells me that Rola supplied many early speakers and that model is (I think) a Rola. I know in the early days of amplification Rickenbacher and Gibson and probably others used field coil speakers provided by Rola. I have a 39 ric that has the original 86 year old speaker and I can crank it up and it still sounds very good.
I had one of the first Gibson EH185 amps (with EH150 stamped on the label) and I know how the schematics don't match the amps. You may find that early Epiphone or National amps or early radios may have used similar circuits that could provide incite to aid in understanding the workings.

[Murray Leshner]

Thanks, all!

[Pete Martin]

If you need the field coil speaker rebuilt, I believe this is about the only place to have it done.

http://www.thespeakershop.com/

I have an EH125 that the field coil was blown and they rebuilt it. Not cheap but they did a GREAT job!!!! Sounds better now than before the fc blew.