Gibson EH-125

[rp]

Tackling that speaker is impressive.

How about a voltage chart?

[martin manning]

Tackling that speaker is impressive.

How about a voltage chart?

Indeed! I think a schematic would be needed to interpret voltages as this example differs from the one available on the web.

[ic-racer]

Amp is all packaged up to test the speaker. Need to flog it a little to see if the repair holds. Then all apart again to trace the schematic and get the voltages.

[ic-racer]

I measured voltages and drew up a schematic. Still working on it, will post when ready.

[ic-racer]

Overdriven sounds EH125:
https://youtu.be/b4xgKfXheEU

Clean sounds EH125:
https://youtu.be/IaYIE8olw28

[ic-racer]

Schematic EH125.

[ic-racer]

Picture of the finished speaker before going back in the cabinet. The repair worked great. Good thing because I could not find a replacement two-coil, 6-ohm, 1" voice coil replacement.

[img768]http://img.photobucket.com/albums/v670/ ... G_1041.jpg[/img]

BTW, if I were going to recone, I'd get my parts from one of these places. They sell the individual cones, spiders and coils so one can recone an 'unknown' speaker.

Speaker Exchange:
http://reconingspeakers.com/product-cat ... ice-coils/

or

Queensland Speaker Repair https://qsr.net.au/product-category/spe ... ice-coils/

[10thTx]

Wow, both of those sound clips are incredibly great sounding, IMO. I especially like the overdriven one.

My favorite clips of yours are still the ManZamp, but the OD tone on this amp is a close second.

THANKS for sharing the clips! With respect, 10thtx

[jazbo8]

It seems your EH-125 is nearly the same as the Kalamazoo KEH. Note that there are some errors on the Gibson schematic, do you see them?

[ic-racer]

Thanks for posting that schematic. Good find. I thought I did a good search but I missed that one.

[Phil_S]

Wow. It all leaves me kinda speechless! Great chops on those clips, too. The whole package!

The schematic should prove to be a great gift to the community. Maybe I'm stating the obvious. It is meant only to be helpful and not meant in any way to be critical.

I see the 6J5 is a cathodyne inverter with unknown plate load resistor. In all probability it is the same as the cathode resistor, 3K.

The unknown from grid to ground on the 6J5 is likely to be fairly high value, maybe 1M.

I'm thinking the input resistor can probably be anything from about 10K to 33K and it wouldn't make much difference, though I completely understand the desire to be authentic. I'll guess at 15K because the other input is a pair of 27K. 15K, AFAIK, is the nearest equivalent standard value. There's no saying that any particular logic applies, though.

Did you forget the show the B+ connection to the output transformer?

Again, what you did is just awesome!

[jazbo8]

I see the 6J5 is a cathodyne inverter with unknown plate load resistor. In all probability it is the same as the cathode resistor, 3K.

Well, no... the 3k is the cathode bias resistor, the cathode load is actually 100k, so the plate load should be 100k in order to keep the two outputs in balance.

[ic-racer]

The resistor is not unknown, I just forgot to write it down. I'll open it up tonight and clean up the schematic.

I haven't mentioned it but I have been thinking this through the whole project. I bet this circuit can hold its own to the popular "tweed deluxe" and is probably worth copying for fun and pleasure. Or at least just to do something different; seems like everyone and their brother has built a "tweed deluxe." Mercury Magnetics has a power transformer for a EH125 build. (GA-EH125-P).

[Phil_S]

My bad on the plate load. 3K seems unreasonably low. Asleep at the wheel?

The dress on the 6SJ7 is not so far off from the GA-20, a much later model. The biggest difference is the high voltage. I like what I heard better than a Fender tweed. Of course, there is no accounting for taste.

[ic-racer]

The schematic in the above post is now updated to v1.6 with all the values.