Gibson GA-9 restoration

[Stevewdewitt]

I have a Gibson GA-9 on my bench. It is in great shape. I think it is a 1948 model. Could be a 58. I have a few questions about the circuit. The schematic is attached. There are 2 10uf 450Vdc caps at the first node after the rectifier. Can these be replaced with 1 20uf 450Vdc cap? The model I have is a little different than the schematic. It has a 20/10/10 450Vdc cap rather than a 10/10/10 450Vdc. Can the 10uf Caps be replaced with 16uf 450Vdc caps? This is being restored for a gigging musician. It needs to be solid.

This thing is in great shape. The tweed is laquered and beautiful. I will attach some pics.

TIA,
Steve

[Stevewdewitt]

more pics

[shooter]

here's Doug's copy;
https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga9.pdf

if it still has the 5Y3, the 1st filter cap shouldn't be bigger than 40uF IIRC

with patience you can probably "gut" the old cap, glue in a modern one and still keep the aesthetic factor

[Willabe]

There are 2 10uf 450Vdc caps at the first node after the rectifier. Can these be replaced with 1 20uf 450Vdc cap? 

Can the 10uf Caps be replaced with 16uf 450Vdc caps?

Yes and yes.

[Willabe]

here's Doug's copy;
https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga9.pdf

The link you posted, ^^^^^^^^^, is a different amp, parallel single ended. His is PP.   

[John]

here's Doug's copy;
https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga9.pdf

The link you posted, ^^^^^^^^^, is a different amp, parallel single ended. His is PP.   

The OP's schematic looks || SE to me.

[Stevewdewitt]

I have a 20/20/10/10 @475Vdc that I am going to use. It will fit right in there. I think I should replace the bumblebee caps as well. I will see if they are leaky. I would also replace the 20uf/25V caps as well. One is cathode bypass and the other seems to be the cathode bias cap.

thanks,
Steve

[Willabe]

here's Doug's copy;
https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga9.pdf

The link you posted, ^^^^^^^^^, is a different amp, parallel single ended. His is PP.   

The OP's schematic looks || SE to me.

         My mistake. You guys are correct. 

[Ritchie200]

Most likely a 58 (unless speaker replaced) as the 56 and earlier had the TV screen fronts.  Regardless, I don't think they made the 9 in the 40's? Can you see date codes on pots?

Jim

[Stevewdewitt]

It is a 1958

[John]

here's Doug's copy;
https://el34world.com/charts/Schematics/files/Gibson/Gibson_ga9.pdf

The link you posted, ^^^^^^^^^, is a different amp, parallel single ended. His is PP.   

The OP's schematic looks || SE to me.

         My mistake. You guys are correct.

Now you know how I feel! 

[shooter]

one of my early builds was a GA-8 PSE 6L6, fortunately Sluckey helped me figure out it wasn't  PP 
That build spawned my affinity for SE 

[Willabe]

Thanks guys.   

When I looked at the 1st drawing, I didn't look at the bottom half of the OT primary. I saw the power tubes and they are shown like PP, stacked, not side by side.