Gibson output transformer--how is it attached?

[nashvillebill]

I'm restoring an Epiphone (Gibson) EA15-RV from around 1961. I've got to strip the chassis to clean up the rust (faceplate was extremely heavily rusted).

How in the Sam Hill did they attach the output transformer to the underside of the chassis? No screws or rivets anywhere! They glued it to the steel chassis!!! This has every indication that it was the way it was originally done 50+ years ago, the glue appears very old, the OT looks old, there's no obvious modifications to the chassis.

Anybody familiar with this?

Incidentally, the schematic matches the Bell Amps BA15RV that's on the Gibson site.

[Tom Phillips]

...How in the Sam Hill did they attach the output transformer to the underside of the chassis? No screws or rivets anywhere! They glued it to the steel chassis!!! This has every indication that it was the way it was originally done 50+ years ago, the glue appears very old...

Definitely a strange one. I have never seen that done in any of the old Gibsons or Epiphones that crossed my path. There is a discussion about the EA-15RV at The Amp Garage :: View topic - Can't find any info on this amp. Anyone know? but there is no mention of any unusual OT mounting. There are photos, including gut shots, posted there and the amp appears to be in original condition. Maybe you can find some useful info in that post. I can't see definitive proof of OT mounting screws. Looks like there just may be points of sheet metal screws showing.
Regards,
Tom

[Tom Phillips]

I have another thought about this. Could it be that the OT tabs are soldered to the chassis and the old dried flux is looking like a glue?

[J M Fahey]

Just guessing: **old** speakers often were offered with a generic output transformer (much smaller than we'd expect because they were guaranteed flat only to 200 Hz) mounted straight to the speaker frame.
More modern speakers still showed the now useless holes in the frame.
Somebody *might* have replaced such a speaker with a transformerless one and soldered/glued the old transformer to a chassis which wasn't expecting it.
A sample of some Tech ingenuity.

FWIW , besides bolting them down, I also contact cement glue *all* transformers to the chassis.
After a couple years they sure are tight.
Often I pull all 4 screws and still have problems to separate them, to the extreme of needing a flat blade screwdriver as a lever.

Started doing that as a backup measure, because I've had my share of cracked transformer mounting ears and "elephant in the bazaar" destruction.

Life in the road is tough.

[nashvillebill]

Thanks for the thoughts!

This sure looks like a factory job, the glue looks that old. By the way, the transformer has been laid on its side at 90 degrees to the PT-- maybe they did that for hum reduction? There are no solder tabs to the chassis there, this is purely glue.

The link at the Amp Garage reference the EA-15RVT with tremolo, which is the later version--completely different tube complement and schematic, unfortunately.

Anyhow, I'll gently break it free with the heat gun (applied to the chassis), then once I clean the chassis, I'll fabricate a mounting bracket...and also use epoxy, I can see how that could help keep it from mechanically vibrating.

[J M Fahey]

Cool, but avoid epoxy; contact cement or maybe some kind of silastic is better in this case because it has some elasticity.

[nashvillebill]

Good point, I'll use contact cement, thanks!

[J M Fahey]

Cool.
Remember it takes around a week to be real strong, it's only a "backup".
After a year it's almost impossible to separate.
Good luck.