Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => PC Express and JSchem - Schematics and Layout diagrams => Topic started by: tubenit on May 26, 2008, 06:12:22 am

Title: Gibson GA-18T, GA-8T & GA-5T
Post by: tubenit on May 26, 2008, 06:12:22 am

Somebody needed a layout to scratch build a GA-18T, so I drew this up. The schematic just shows one input jack with 27k value & I added some 470 ohm resistors to the 6V6 screens.

Apparently, there are at least three different GA-18/GA-18T versions. This one is the tweed style with 12AX7's (not 6EU7's), 6V6's (not EL84's) & a 5Y3 rectifier (not 6CA4).

With respect, Tubenit

Title: Re: Gibson GA-18T & GA-8T
Post by: tubenit on June 16, 2008, 05:33:44 am

 This is the Gibson GA-8T/Epiphone EA-35T amp & Gibsonette amp.

Also the GA -5T.

Check for errors. Compare to original copies on Schematic Heaven

Title: Re: Gibson GA-18T, GA-8T & GA-5T
Post by: lego4040 on April 19, 2014, 12:59:06 pm

Tubenit, I Just found this and I was wondering what program I need to open this GA18T layout? My windows does not recognize. I think Id like to do Gibsons GA18T version of Fenders tremolux since I have a extra matched set of EL84's. I know you made this layout for the 12ax7 and 6v6's but if I just changed the pins back to the EL's and 6Eu7 would that work?

Title: Re: Gibson GA-18T, GA-8T & GA-5T
Post by: lego4040 on April 19, 2014, 01:34:23 pm

I found the link here to open sch. the expresspcb program. I can view layout now but I still would like to know what needs to be one to use the El84's?

Title: Re: Gibson GA-18T, GA-8T & GA-5T
Post by: sluckey on April 19, 2014, 04:14:26 pm

The GA-18T is a 6BQ5 amp. Just lookup the original schematic in Doug's schematic library.

Title: Re: Gibson GA-18T, GA-8T & GA-5T
Post by: lego4040 on April 19, 2014, 05:18:35 pm

I printed out both the 16T and 18T for reference and wrote down pins for both the 6v6/12ax7 version and the el84/6? Version. I read they are same circuit but I already see different values on input resistors