Gretsch Chet Atkins Piggyback 6169 Bias ?

[gtrplayr1976]

I'm now trying to get this amp working. Mid 60s (66 maybe) Gretsch Chet Atkins 6169. This schematic is for a 6169 Fury. It seems very similar so far. The only thing I see different for sure is the speaker out. The Fury has a single output jack while the CA has a main ,and an ext. My friend says one side is getting really hot. I can tell by the tubes. It is suppose to have 6l6GCs ,but has 5881s. I will be replacing all of the 35/50 caps. Not sure if I can find the cans. They are 20/10/10 ,and there are five of them. Some look like they are paralleled , so might be able to use different can values ? I have absolutely no clue on the biasing this one either. I've never worked with anything like this to my knowledge.
I'll post some gut shots also. I see something that looks like leakage around the OTs.
Amp is super clean (except for dust ,and whatever that residue is on top of the chassis)

Thanks all !

[mozz]

I see at least 6 wax caps, get rid of those or restuff. Some 5881's are only rated the same plate voltage as 6l6gb's, so measure that too. Looks like a nice project. The leakage may be a drink or soda, or capacitor leakage. Cathode bias on the output tubes, no need to adjust, just measure, calculate and be sure it's within spec.

[The Dude]

A few of thoughts:

It's a stereo amp, so you can compare voltages from the good side to the side that's getting hot. It might help steer you in the right direction.
Each side has a 200 ohm cathode resistor. I'd start by checking the voltage drop across those and figure your bias for each amp.
And, Mr. Obvious says you should replace that green wire in photo #3.

[g1]

The 6169 has 2 separate power amps. That is a stereo (TRS) speaker jack. One power amp connects to the tip, one power amp connects to the ring. The cab shown is wired with a stereo jack the same way, one speaker to tip, one speaker to ring.
If yours is wired the same way and you put in a mono speaker cable, one power amp will be running into a dead short and I expect it would get hot.
You need to figure out the OT and speaker jack wiring and draw a schematic if it is different from the 6169 for that part of the circuit.

[gtrplayr1976]

I see at least 6 wax caps, get rid of those or restuff. Some 5881's are only rated the same plate voltage as 6l6gb's, so measure that too. Looks like a nice project. The leakage may be a drink or soda, or capacitor leakage. Cathode bias on the output tubes, no need to adjust, just measure, calculate and be sure it's within spec.

Aren't the 5881s 23 watt ,and the 6l6gcs are 30 watt ? That would throw the bias off would it not ? I know this guy ,and I doubt he spilled anything. The outside of the amp looks fantastic.

[gtrplayr1976]

The 6169 has 2 separate power amps. That is a stereo (TRS) speaker jack. One power amp connects to the tip, one power amp connects to the ring. The cab shown is wired with a stereo jack the same way, one speaker to tip, one speaker to ring.
If yours is wired the same way and you put in a mono speaker cable, one power amp will be running into a dead short and I expect it would get hot.
You need to figure out the OT and speaker jack wiring and draw a schematic if it is different from the 6169 for that part of the circuit.

The amp I have is not this amp on the schematic even though they have the same model number. The Chet Atkins has different outputs. A main ,and an ext. The picture of the entire back is the Fury. Single output.

[gtrplayr1976]

A few of thoughts:

It's a stereo amp, so you can compare voltages from the good side to the side that's getting hot. It might help steer you in the right direction.
Each side has a 200 ohm cathode resistor. I'd start by checking the voltage drop across those and figure your bias for each amp.
And, Mr. Obvious says you should replace that green wire in photo #3.

The Chet Atkins isn't stereo. That's one of the differences. I found one of the cathode caps on pin 8 of the power tubes bad ,and yes I will be replacing that wire.

[g1]

I'm not sure if you understand how a TRS jack works. It can be wired up so it is like 2 separate jacks. So the Fury is not single output.
Can you post some pics of the jacks wiring and where the wires go to.

[The Dude]

Despite the jacks being labeled Main and External, I see two output transformers and you say there are two cathode caps, matching the schematic. That means it is a stereo amp. It should not be run without two independent speaker loads. It could be that both jacks are mono and one goes to each amp, or it could be that each is a stereo jack. As g1 says, you need to figure out how the jacks are wired.

[The Dude]

In your picture #4, I see only one wire going to a mono external speaker jack. I can't see pic #5 speaker jack good enough to tell what's going on there.

[gtrplayr1976]

Despite the jacks being labeled Main and External, I see two output transformers and you say there are two cathode caps. That means it is a stereo amp. It should not be run without two independent speaker loads. It could be that both jacks are mono and one goes to each amp, or it could be that each is a stereo jack. As g1 says, you need to figure out how the jacks are wired.

I need to see the cabinet to see what it looks like. He didn't bring that with him. The one external jack looks like a regular jack. Hard to see the main in these pictures. I'll try to draw out the output circuits. Got another shot of the main. It DOES look to be stereo.

[52 Bill]

The photos of the chassis in the first post show that the jack on the left side (main speaker) is a stereo jack.

The entire amp is not stereo, but it has two power output sections to make a louder amp, probably to save the cost of a larger output transformer. This is typical of a few Supro amps made for Wards, Gretsch, etc.

The leakage around the transformers looks like wax from the overheating. The one photo shows a really dark interior on the one output transformer, like it got hot.

[The Dude]

In this particular instance, since it is a stereo/dual amp, I would definitely ask him to bring in the cabinet and speaker cable(s) he is using to make sure that he is indeed running two loads. There is a good chance he has it wrong.

[gtrplayr1976]

The photos of the chassis in the first post show that the jack on the left side (main speaker) is a stereo jack.

The entire amp is not stereo, but it has two power output sections to make a louder amp, probably to save the cost of a larger output transformer. This is typical of a few Supro amps made for Wards, Gretsch, etc.

The leakage around the transformers looks like wax from the overheating. The one photo shows a really dark interior on the one output transformer, like it got hot.

It is Bill. I just saw it myself. I'm wondering if they were using a mono jack ,and THAT was causing the overheating ?

[gtrplayr1976]

In this particular instance, since it is a stereo/dual amp, I would definitely ask him to bring in the cabinet and speaker cable(s) he is using to make sure that he is indeed running two loads. There is a good chance he has it wrong.

I added another good photo that shows the jack is indeed stereo. They very well may have been using a mono jack. I'll talk to him about that.