Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Cock Robin on August 19, 2016, 08:33:09 am

Title: Gibson GA-15RVT parts help
Post by: Cock Robin on August 19, 2016, 08:33:09 am

Help! Looking for parts - well, part - for my Gibson GA-15RVT. Specifically I need the transformer labeled T3 on the schematic. It's coming off the tremolo circuit and acting as a phase inverter (which is usually done with a tube - Gibson seems to have gone out of their way to have a "unique" design). The schematic is in the schematic library, but apart from showing the transformer location it gives no details on the transformer (or really any usable info).

Without this transformer the amp is basically dead in the water, and the usual tricks (like by-passing it entirely) don't seem to work. It has to be there for whatever reason.

Anyone either know of a source for this transformer, or at least its specs? Or maybe know a work around? I really like this little amp and I hate to lose it for such a dumb reason.
--
Robin

Title: Re: Gibson GA-15RVT parts help
Post by: shooter on August 19, 2016, 09:43:37 am

I used this to fix a GA5T and also used it on one of my builds as the PI
http://www.triodeelectronics.com/unintrui.html (http://www.triodeelectronics.com/unintrui.html)

Title: Re: Gibson GA-15RVT parts help
Post by: mresistor on August 19, 2016, 09:46:06 am

I assume you are talking about T3 in the schematic


I have something similar that was in either a Baldwin Orgasosnic or a Hammond S-6 organ. It might work for you. Looks like a non-tapped primary and a center tapped secondary. I don't know the specs and don't really know how to check it other than apply some voltage to it and see if it steps up or down, you know try to find the turns ratio. maybe someone else here could help us with that? I can say that the output circuit looks similar to some I have seen in organ schematics.


 

Title: Re: Gibson GA-15RVT parts help
Post by: sluckey on August 19, 2016, 09:51:29 am

Mercury Magnetics has a couple. Scroll down to the Phase Inverter section...

     http://www.mercurymagnetics.com/pages/catalog/manufacturers/MM_gibson.htm (http://www.mercurymagnetics.com/pages/catalog/manufacturers/MM_gibson.htm)

Title: Re: Gibson GA-15RVT parts help
Post by: mresistor on August 19, 2016, 09:56:10 am

This one is out of a Hammond s-6   organ   and if you want it you can have it for postage cost.

Title: Re: Gibson GA-15RVT parts help
Post by: mresistor on August 19, 2016, 10:00:43 am

 I have seen that TF-1001-D trans mounted on a GA-15RVT, and as always  MM has a nice price... 


If it helps the transformer I have was driven by a 12AU7 on the input and the output was to two 6BA6 pentodes (remote-cuutoff)

Title: Re: Gibson GA-15RVT parts help
Post by: sluckey on August 19, 2016, 10:02:33 am

I bet that Hammond transformer will work just fine.