andresound wrote:Played the amp for an hour last night. Really good sounding amp (it has MOJO)
![Laughing :lol:](./images/smilies/icon_lol.gif)
Awsome sounding reverb!! I will go through the entire circuit this weekend and check every component and voltages.
That's awesome news!
Few things I noticed.
1. Although the amp had a bit of paperwork with it, which states it is a EA-10RV, the circuit looks to be a GA-77RV.
Typically there is an equivalent Epiphone model to each Gibson. Minor variations are known to be rampant from this manufacturer. I have a Gibson GA20-RVT of which there are two "known" versions, of which I have the 3rd. I you have a match on the tube compliment, general circuit (i.e., both have reverb,similar tones stack, etc.), transformers, speaker, and cab, I'd consider it a match. If you can't determine some of this, go with tubes and general circuit for a match. Sometimes transformer part numbers appear on the schematics, sometimes not.
2. At turn on, the amp has a slight bit of mains hum, which is constant.
Not surprising in an amp this age. It probably needs a grounded power cord and a cap job. It is surprising what these two routine maintenance items will do. I'd suggest changing ALL of the electrolytic caps on account of their age.
3. The filter caps in the amp I will change, but.... The values of the big yellow ones in the pic and the other ones are very different to the GA-77RV schem. The first filter cap before the recto is shown as a 20uf, and the following ones are 10uf. All the caps installed are higher.
The originals would probably be wrapped in brown paper with a metal band riveted to the chassis. See the picture. If they are original, just stick with the values. If not, there is nothing wrong with 20-10-10 (or whatever). All 20's seem like a good choice to me. 20uf, 22uf, and 25uf are all functionally equivalent in this instance, so buy whatever is most appropriate for your budget and with respect to size/style for fitting them to the amp. Pay attention to voltage ratings as you don't want to go below what you see on the B+ rail and you want some headroom above the B+ rail voltage. Any new cap you buy will be of considerably higher quality compared to what the amp was built with.
Seems like you have a great find!
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