Ampeg Gemini II wiring help needed

[Rich Rice]

Hello everyone, thanks for clicking on my thread. I just bought a '66 (I think) Gemini II, which has a broken mount on the multi cap. I was aware the cap can was hanging by the wires, and that channel 1 was non operational. The seller told me there was one green wire that had come off a lug, so I decided to buy it anyway- figuring I could find the lug and resolder.. well.....
The amp arrived yesterday, and there are 4 wires floating around in there-- I'm not sure where they should go. I haven't tubed the amp or powered it up, as I don't want to cause further damage, but am anxious to use the amp. Anybody out there familiar with this arrangement? Thanks in advance!

[52 Bill]

From the looks of the wiring, your amp is a Gemini VI model GS-15-R. Go to schematic heaven and download the schematic.

First things first, repair or replace the phenolic mounting ring that has been broken. I think you can still order them from either fliptops or antique electronics.

The filter can is a 3 X 40uF cap, right? Two sections are paralleled to create an 80uF cap that is used as the first filter. The red wire still attached to the 2 center terminals should go to the output transformer center tap. There should also be a wire that goes to the two power supply diodes. Follow the brown wire and see if it could connect to the junction of the two diodes. There is a red wire that is attached to the right side of the 470R resistor that feeds the other power supply nodes. This should also attach to the same center terminal.

I can't see where the green wire goes to. The filter cap third terminal needs to connect to the left side of the 470R resistor. If the green wire goes to the left side of the 470R, then it should connect to the single cap terminal that also attaches to the red wire that goes to the screens of the output tubes (pin 4&8).

The black wire that goes to the board near the bias filter cap should be a ground connection. This will attach to the filter cap outside can terminal.

Hope this helps.

[Rich Rice]

Thanks so much for your help. This is a Gemini II, G-15 model. Your advice was very helpful, and I appreciate it. We had figured out the connections, and the amp is operational. Your post gave us a basis for comparison, to verify that we had everything in the proper places. This amp has other issues, but this was one that really had us worried.

Both channels worked perfectly for a few minutes, then some very loud scratchy sounds came booming through the speaker. We swapped out the tubes, and seem to have isolated one socket that is intermittent, also the control panel became microphonic. If I hold the problematic tube in just the right spot, channel 1 will work. I'm not sure if it is a dirty socket or if there are more problems inside, near the socket. Channel 2 seems to be more stable. When it's working, the amp sounds great... I guess we'll sort out the intermittent problems one at a time. We just ran out of time for today. Again, thank you for your help!

Rich

[Rich Rice]

Quick follow-up

I just played through the "bad" channel for over an hour at performance levels. Not a trace of the crackling noise. Looks like the tube socket for one of the 12AX7's needs some attention, but it seemed to hang in there through some pretty aggressive volume. Looks like some light at the end of the tunnel. Thanks again, Bill. Really good information. I'm so glad to have found this forum.

[Rich Rice]

Well, it's still going strong. I've gigged it a few times, without any problems. I dragged a SF Pro Reverb to the first gigs as a backup, but didn't need it. Looks like the repairs worked fine. This is a cool old amp, with outstanding sound. Thanks again for the help!