Gibson GA-30 need help picking capacitors

[delray]

I bought a GA30 (3 knob version) at a local estate sale. It is in very good condition and surprisingly when I started it up on an auto transformer it works great. No static in the knobs, clean signal, no humming. The two prong power cord is falling apart and for safety's sake it should be replaced with a 3 prong.  I was planning to replace all the caps as well but since it does work Im tempted to leave them original.

Looking at the schematic from this site it looks like I need the following:

4x  10uF
2x  20uF
4x  .05uF
2x .00025uF (250 pF)
1x  .02uF
1x .0007uF (700 pF)

I am a novice at all of this so one thing that's hard for me is to determine what voltage I need from a given schematic. A lot of times you can read what's in there now and replace it but these have really faded over the years. I assume the 10uf coming off the transformer will need to be 600v but what type should I select? Ideally I could order a "rebuild kit".

[bmccowan]

Lucky find - very cool amp. Those big orange 10 and 20uf capacitors are the filter capacitors. I think those should be replaced. F&T is a good brand. 475v and 500v is what you will find and they will be fine. The only reason to keep those original would be if you planned to sell the amp to a collector. If you plan to play the amp - its risky to trust filter caps that old. You do not want to fry the PT.
That and the 3 prong cord are a good start.
You can save the old filter caps if someone down the road thinks it makes the amp more valuable.

[sluckey]

The 4x10s are electrolytic. Use 500V.

The 2x20 are electrolytic. Use 22µF@50V. BTW, I only count one 20µF.

Use 500V caps for everything else.

Everything you need is available at the bottom of this page.

[bmccowan]

Right right - the filter caps are all 10s in that amp. I was too excited by your estate sale find to look at the schematic BTW - speaking of schematics, you may run into some confusion as Gibson used the model no GA25 and GA30 on some identical all octal amps - and took minor detours on capacitor and resistor values.

[delray]

Right right - the filter caps are all 10s in that amp. I was too excited by your estate sale find to look at the schematic BTW - speaking of schematics, you may run into some confusion as Gibson used the model no GA25 and GA30 on some identical all octal amps - and took minor detours on capacitor and resistor values.

Yeah it seems like there are a few of the "GA30" ... some with two knobs, later models, earlier models.

[delray]

Lucky find - very cool amp. Those big orange 10 and 20uf capacitors are the filter capacitors. I think those should be replaced. F&T is a good brand. 475v and 500v is what you will find and they will be fine. The only reason to keep those original would be if you planned to sell the amp to a collector. If you plan to play the amp - its risky to trust filter caps that old. You do not want to fry the PT.
That and the 3 prong cord are a good start.
You can save the old filter caps if someone down the road thinks it makes the amp more valuable.

Thank you.

[delray]

The 4x10s are electrolytic. Use 500V.

The 2x20 are electrolytic. Use 22µF@50V. BTW, I only count one 20µF.

Use 500V caps for everything else.

Everything you need is available at the bottom of this page.

Thank you.

[bmccowan]

Right right - the filter caps are all 10s in that amp. I was too excited by your estate sale find to look at the schematic BTW - speaking of schematics, you may run into some confusion as Gibson used the model no GA25 and GA30 on some identical all octal amps - and took minor detours on capacitor and resistor values.

Yeah it seems like there are a few of the "GA30" ... some with two knobs, later models, earlier models.

And some have a different tube layout - some have 6Sq7s - some have 6Sc7s - some have the "tone expander" which alters the negative feedback and some do not. I think they had a lot of fun in the Gibson workshop in those days. I have an amp that is labelled GA-25 that is exactly like yours. Your amp is in better cosmetic shape and looks all original except for the speaker out jack that was obviously added later.
I note that the handle is giving out. You can buy that exact handle, Its nice to save the patina of the old handle hardware. You can carefully drill out the center pin and insert a new pin. There are probably 100 YouTube vids about doing that.

[delray]

Right right - the filter caps are all 10s in that amp. I was too excited by your estate sale find to look at the schematic BTW - speaking of schematics, you may run into some confusion as Gibson used the model no GA25 and GA30 on some identical all octal amps - and took minor detours on capacitor and resistor values.

Yeah it seems like there are a few of the "GA30" ... some with two knobs, later models, earlier models.

And some have a different tube layout - some have 6Sq7s - some have 6Sc7s - some have the "tone expander" which alters the negative feedback and some do not. I think they had a lot of fun in the Gibson workshop in those days. I have an amp that is labelled GA-25 that is exactly like yours. Your amp is in better cosmetic shape and looks all original except for the speaker out jack that was obviously added later.
I note that the handle is giving out. You can buy that exact handle, Its nice to save the patina of the old handle hardware. You can carefully drill out the center pin and insert a new pin. There are probably 100 YouTube vids about doing that.

I would like to replace the handle and I was going to order one here but it looks like they are no longer sold? Who make a good reproduction?

[sluckey]

https://www.mojotone.com/cabinets/cabinet-parts-hardware/handles?page=1

[rafe]

Those non-electrolytics might be fine, I wouldn't chance the electrolytics either. I am seriously thinking of building one of those testers Mr. Carlson designed.....or finding an old magic eye tester. If the amp has Allen Bradley resistors they are likely good too, but worth testing Nice amp.

[Platefire]

Wow! That amp is so nice. Great Find. I had a 1960 GA40 LP amp but it was down to bare wood cab when I got it. I re-tweeded it. My Son ended up with it.