I finally did a much needed rebuild of my old Gibson guitar amp - and since I had no luck finding an accurate schematic of this model, I reverse engineered the whole thing. I thought others might find it useful.
This is the same model used by the famous jazzer Charlie Christian. One 12" field coil speaker, about 15 watts output.
http://members.aol.com/Junip/images/gibsoneh-150.jpg
This is the same model used by the famous jazzer Charlie Christian. One 12" field coil speaker, about 15 watts output.
http://members.aol.com/Junip/images/gibsoneh-150.jpg
...Sacrilege can be fun...
Hi Joel
James said:
"Have you tried a more modern guitar speaker with it?"
Joel replied
"Blasphemy! Certainly not."
I wouldn't suggest that you replace the origonal speaker....Never
But it might be an interesting data point to try the amp into, say, a Vintage Blue and hear the tone...
My experience with early speakers are that they don't have as much bite as 60's and later speakers... "woody" indeed! But that the amps can be very, very good and it makes an interesting contrast to the origional tone. I have modified a couple of late 40s combos with a speaker out jack and so can plug them into a cab for a different tone palete...
I really like early guitar amps (pre marshalls) into their own speakers and into modern speakers... depends whether my boys are playing delta blues or 'clapton'!
It doesn't make my bass sound like a double bass though...
Nice touch!
ciao
James
Hi Joel
James said:
"Have you tried a more modern guitar speaker with it?"
Joel replied
"Blasphemy! Certainly not."
I wouldn't suggest that you replace the origonal speaker....Never
But it might be an interesting data point to try the amp into, say, a Vintage Blue and hear the tone...
My experience with early speakers are that they don't have as much bite as 60's and later speakers... "woody" indeed! But that the amps can be very, very good and it makes an interesting contrast to the origional tone. I have modified a couple of late 40s combos with a speaker out jack and so can plug them into a cab for a different tone palete...
I really like early guitar amps (pre marshalls) into their own speakers and into modern speakers... depends whether my boys are playing delta blues or 'clapton'!
It doesn't make my bass sound like a double bass though...
Nice touch!
ciao
James
Hey Joel,
I realize this thread is pretty old, but if you're still out there, thanks a million for posting your EH-150 amp schematic.
I was just about to embark on the same reverse-engineering project for my 1937 EH-150 after coming up empty handed when searching the web. You've saved me a tremendous amount of time.
Now I can get the electronic restoration done and start playing that little tweed, round-shouldered cutie.
By the way, the only difference I noticed in my amp is a center-tapped secondary on the output transformer for the "echo" speaker jack. Also, to anyone trying a later PM speaker in place of the field-coil speaker (if you really insist on doing this), just remember to leave the field wires connected to the old speaker. It does double-duty as a filter choke in the power supply.
Thanks again Joel....
I realize this thread is pretty old, but if you're still out there, thanks a million for posting your EH-150 amp schematic.
I was just about to embark on the same reverse-engineering project for my 1937 EH-150 after coming up empty handed when searching the web. You've saved me a tremendous amount of time.
Now I can get the electronic restoration done and start playing that little tweed, round-shouldered cutie.
By the way, the only difference I noticed in my amp is a center-tapped secondary on the output transformer for the "echo" speaker jack. Also, to anyone trying a later PM speaker in place of the field-coil speaker (if you really insist on doing this), just remember to leave the field wires connected to the old speaker. It does double-duty as a filter choke in the power supply.
Thanks again Joel....
cavalino said:
Interesting, I looked at the Gibson service manual thats downloadable
Click Here Adobe Needed
And there are 2 entirely different schematics for that model.
The one posted in the original thread here is Similar but not exact. Possibly a 3rd Version of the EH150?
I have a really nice field coil speaker from a Vintage Stromberg Carlson Unit I had planned on using to build one of Gibsons early amps as a winter project. So I had downloaded the entire manual. 128 or so megs!!!
Gene
Trout said:
Yes... the schematic in this post is a third version of the amp. It is sort of a "hybrid" of the two schematics you found (i.e. using a transformer instead of a 6N7 as a phase inverter tube, 6L6 output tubes instead of 6N6 dual triodes, etc.)
Good luck with your eh-150 project. I'd be interested in hearing about the sound you get from the Stromberg speaker. I don't know if the Stromberg's field coil is the same inductance as the Gibson's coil, but the B supply should be pretty forgiving.
Jim
J Epstein said:
You're right. the "EH" stands for "Electric Hawaiian". The amp was sold as a set which included a beautiful Hawaiian lap-steel guitar which is also called an EH-150. The "150" part of the name was actually the selling price of the amp and guitar set.
This amp was really made famous by the great Charlie Christian who played an "ES-150" archtop guitar with it. The "ES" stands for "Electric Spanish" and Gibson still uses it with most of its archtops/hollowbodies today.
I repair & tune guitar amps in lower NW MI. I got in an old Supro field coil 12" model with PP 6V6GTs. It had a 6J5 preamp & I believe a 6SC7 driver plus 5Y3GT rectifier.
This amp blew all of us away with the incredable sonics. Cranked full tilt, this amp screams out blues & rock like no other amp I ever heard. The Supro 1624 dual tone with the Rola 12" (not later models with the Jensen P12R) is close in performance.
This amp blew all of us away with the incredable sonics. Cranked full tilt, this amp screams out blues & rock like no other amp I ever heard. The Supro 1624 dual tone with the Rola 12" (not later models with the Jensen P12R) is close in performance.
Hey Amperex, I'm down here in Lansing sitting in my amp shop.
Gibson is infamous for the schematics not matching the amp. They often and rather liberally changed the innards of their amps through the production runs. I have the paper copy of that MAster Manual, and I often have to leaf through it to find the schematic for somethhng that is other than it seems. SOmetimes the Epiphone drawing fits the Gibson model and vice versa.
I have serviced three different GA15RVT in recent times and each was different. One matched the book, and the other two I had to draw the schematic by hand. Not a rare occurrance with Gibsons.
Gibson is infamous for the schematics not matching the amp. They often and rather liberally changed the innards of their amps through the production runs. I have the paper copy of that MAster Manual, and I often have to leaf through it to find the schematic for somethhng that is other than it seems. SOmetimes the Epiphone drawing fits the Gibson model and vice versa.
I have serviced three different GA15RVT in recent times and each was different. One matched the book, and the other two I had to draw the schematic by hand. Not a rare occurrance with Gibsons.
cavalino said:
The 12 inch Stromberg Carlson Field coil speaker I have has a 850 ohm coil, Darn near a perfect match for a clone version of the eh(or at least in 1 or more of its versions).
The Original Stromberg amp that drove the speaker had a pair of 6V6Gts driving it. I also have the original OPT, But Seeing as it was more or less a Amplified Victrola(78rpm only) I suspect the OPT wont exactly cut the mustard so to speak.
The Speaker appears rock solid though, Clean as new.
If I wasnt in the middle of 3 other projects + Honey Dues I would be already building it.
Gene
Thanks a Million
Joel,
I also would like to thank you if you're still around.
I have spent countless hours searching the web and calling techs all over the country looking for this schematic.
I had originally contacted Gibson and it was not one that they had in their records (although they sent me the other 2) and Schematic Heaven before Miles, Aspen, Rudy, Rich, and many, many others.
Thank all of you for your patience (if you happen to read this) but mostly, I want to THANK YOU for getting me to this milestone with my EH-150's.
Sincerely,
Jim Dilworth
Joel,
I also would like to thank you if you're still around.
I have spent countless hours searching the web and calling techs all over the country looking for this schematic.
I had originally contacted Gibson and it was not one that they had in their records (although they sent me the other 2) and Schematic Heaven before Miles, Aspen, Rudy, Rich, and many, many others.
Thank all of you for your patience (if you happen to read this) but mostly, I want to THANK YOU for getting me to this milestone with my EH-150's.
Sincerely,
Jim Dilworth
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