Gibson EH-125
Moderators: pompeiisneaks, Colossal
Re: Gibson EH-125
The standard power transformer in the EH-150s was T-40069, wound by Thordarson in Chicago. It is 408-0-408VAC.
Re: Gibson EH-125
My EH-125 came in the mail today.
First thing I checked was that V1 plate resistor and, indeed, it is a 1 Meg resistor. My amp works fine, all the capacitors have been professionally replaced and it works great, so 1 Meg goes on the schematic.
Turns out my amp just has a bad speaker.
First thing I checked was that V1 plate resistor and, indeed, it is a 1 Meg resistor. My amp works fine, all the capacitors have been professionally replaced and it works great, so 1 Meg goes on the schematic.
Turns out my amp just has a bad speaker.
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
I'll go into detail on the speaker since the thread is already going. (pictures to follow).
The speaker looks original, it is 6 ohm field coil. It has a few problems:
1) Weak paper surround
2) saggy spider
3) voice coil rubs
4) half of the cone got wet or mildew making it a little out of round.
Since I had blocked off some time to fix the amp, and it is already perfect, I decided to try to fix the speaker. I have re-coned speakers and in this case I wanted to try and re-cone the speaker with its own original parts. I'm sure many of you have experienced the special jive that comes from an old speaker.
First I removed the dust cap (just a piece of felt) and shimmed the voice coil. Then I sprayed 409 on the cone and spider making them soggy wet. Then set the voice coil so the spider was flat and let it dry that way. This actually worked, the spider and cone firmed up in the proper configuration.
The paper surround was weak, so I diluted some latex glue with water and doped the paper surround to firm it up (again with the voice coil shimmed).
This seemed to work great, but still the coil rubbed. Why??
Turns out the field coil had come un-glued and that was causing the rubbing.
The speaker looks original, it is 6 ohm field coil. It has a few problems:
1) Weak paper surround
2) saggy spider
3) voice coil rubs
4) half of the cone got wet or mildew making it a little out of round.
Since I had blocked off some time to fix the amp, and it is already perfect, I decided to try to fix the speaker. I have re-coned speakers and in this case I wanted to try and re-cone the speaker with its own original parts. I'm sure many of you have experienced the special jive that comes from an old speaker.
First I removed the dust cap (just a piece of felt) and shimmed the voice coil. Then I sprayed 409 on the cone and spider making them soggy wet. Then set the voice coil so the spider was flat and let it dry that way. This actually worked, the spider and cone firmed up in the proper configuration.
The paper surround was weak, so I diluted some latex glue with water and doped the paper surround to firm it up (again with the voice coil shimmed).
This seemed to work great, but still the coil rubbed. Why??
Turns out the field coil had come un-glued and that was causing the rubbing.
Last edited by ic-racer on Sun Nov 08, 2015 1:26 am, edited 2 times in total.
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
To reglue the field coil I needed to shim it. The only way to do that would be to take off the cone and spider...but, maybe I can carefully cut out the voice coil.
In fact, that is what I did. I used an Exacto to cut the voice coil and remove it. Turns out it is in perfect shape. no loose wires, no burning, no distortion of the form. A new 6-ohm 1" coil may be hard to come by, so I'll try to re-use it.
With the voice coil out, I can shim the field coil. That is how it is right now. I'll leave it like that and get some glue in the morning.
After re-gluing the field coil with epoxy, I'll re-shim the voice coil and epoxy it from the outside and inside the cone, re-connecting it to the spider and cone.
In fact, that is what I did. I used an Exacto to cut the voice coil and remove it. Turns out it is in perfect shape. no loose wires, no burning, no distortion of the form. A new 6-ohm 1" coil may be hard to come by, so I'll try to re-use it.
With the voice coil out, I can shim the field coil. That is how it is right now. I'll leave it like that and get some glue in the morning.
After re-gluing the field coil with epoxy, I'll re-shim the voice coil and epoxy it from the outside and inside the cone, re-connecting it to the spider and cone.
Last edited by ic-racer on Sun Nov 08, 2015 5:09 pm, edited 1 time in total.
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
Man, you do some brave shit. I am in awe. I don't know if it could be helpful, but there is a Wood Hardener product designed for wood rot scenarios. Goes on wet, drives out moisture, dries firm but flexible.
Re: Gibson EH-125
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
This is the amplifier as it came to me.
[img
768]http://img.photobucket.com/albums/v670/ ... hassis.jpg[/img]
[img
768]http://img.photobucket.com/albums/v670/ ... hassis.jpg[/img]
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
Voice coil out. Shims to re-glue the field coil.
[img768]http://img.photobucket.com/albums/v670/ ... 20coil.jpg[/img]
[img
768]http://img.photobucket.com/albums/v670/ ... 20coil.jpg[/img]
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
Epoxy for the voice coil. It was only glued at the far end. I worked the epoxy under the coil with pieces of cardboard.
[img768]http://img.photobucket.com/albums/v670/ ... 20Coil.jpg[/img]
[img
768]http://img.photobucket.com/albums/v670/ ... 20Coil.jpg[/img]
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
Bad news: one whisker broke off the voice coil. Good news is that I was able to solder a new one in place. Also, my first measurement of the coil was wrong. It is 1" which is an available size (though not in 6 ohm).
[img768]http://img.photobucket.com/albums/v670/ ... 20Lead.jpg[/img]
[img
768]http://img.photobucket.com/albums/v670/ ... 20Lead.jpg[/img]
Last edited by ic-racer on Wed Nov 11, 2015 6:45 pm, edited 1 time in total.
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
Voice coil shimmed in place. I measured to make sure it was not sitting lopsided.
[img768]http://img.photobucket.com/albums/v670/ ... 20Coil.jpg[/img]
There was a 1/8" gap around the voice coil and the cone. How to connect the two? I used this piece of twine. I wrapped it around the voice coil between the spider and the cone. It filled the gap between the cone and the voiced coil (from underneath) and soaked up the epoxy for a firm bond.
[img768]http://img.photobucket.com/albums/v670/ ... G_1024.jpg[/img]
[img
768]http://img.photobucket.com/albums/v670/ ... 20Coil.jpg[/img]
There was a 1/8" gap around the voice coil and the cone. How to connect the two? I used this piece of twine. I wrapped it around the voice coil between the spider and the cone. It filled the gap between the cone and the voiced coil (from underneath) and soaked up the epoxy for a firm bond.
[img
768]http://img.photobucket.com/albums/v670/ ... G_1024.jpg[/img]
Last edited by ic-racer on Wed Nov 11, 2015 8:55 pm, edited 2 times in total.
"You feel like you're floating on a football field filled with marshmallows." -Dumble
Re: Gibson EH-125
Amp and speaker sound great. Sound clips and more pictures to come.
"You feel like you're floating on a football field filled with marshmallows." -Dumble