Gretsch Chet Atkins Piggyback 6169 Bias ?

[gtrplayr1976]

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.

I got the jacks posted ,and you are correct it is a stereo jack on the main. I'll try to get some of where the wires actually go although they probably match the schematic ?

[The Dude]

Yep. That is stereo and shorting- like Fenders only stereo. With nothing plugged in, both amp's OT's are shorted to ground. My guess, like your guess, is that they were using a mono jack and one side of the amp was shorted to ground via the jack- causing heat and a failure of the cathode resistor on that amp.

[gtrplayr1976]

Yep. That is stereo and shorting- like Fenders only stereo. With nothing plugged in, both amp's OT's are shorted to ground. My guess, like your guess, is that they were using a mono jack and one side of the amp was shorted to ground via the jack- causing heat and a failure of the cathode resistor on that amp.

I'm trying to gather some info from the owner. I really hope it didn't ruin it.

[The Dude]

Everything is fixable.

[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.

I think the only difference is the added jack which is connected pretty much like this drawing.

[g1]

That's how it looks to me too. The ext. jack just adds a parallel speaker to one of the power amps.

[gtrplayr1976]

That's how it looks to me too. The ext. jack just adds a parallel speaker to one of the power amps.

How does that work impedance wise ?

[g1]

It's like adding an ext. speaker to any other amp that does not have an impedance selector.
The load impedance will depend on the impedance of the regular cab speaker and the ext. speaker. (R1 times R2) divided by (R1 plus R2).

[gtrplayr1976]

It's like adding an ext. speaker to any other amp that does not have an impedance selector.
The load impedance will depend on the impedance of the regular cab speaker and the ext. speaker. (R1 times R2) divided by (R1 plus R2).

I think the other two speakers are 8ohm each , but they are each fed by their own xfmr ,and the ext is connected to only one xfmr ? I think I need to look at it again. lol

[g1]

You are correct. So if they are 8 ohm speakers, and you add another 8 ohm ext. speaker, one amp is driving an 8 ohm load, the other will be driving a 4 ohm load (two 8R speakers in parallel).

[gtrplayr1976]

You are correct. So if they are 8 ohm speakers, and you add another 8 ohm ext. speaker, one amp is driving an 8 ohm load, the other will be driving a 4 ohm load (two 8R speakers in parallel).

Yes that makes sense. So it would probably be wise to use an 8 ohm ext if using one at all ? I have no idea what the xfmr will handle.

[gtrplayr1976]

You are correct. So if they are 8 ohm speakers, and you add another 8 ohm ext. speaker, one amp is driving an 8 ohm load, the other will be driving a 4 ohm load (two 8R speakers in parallel).

If I need to adjust bias on this one, where would that be done ? This is a whole different setup than I'm use to. I have a bias probe ,but not sure it works with cathode bias?

[The Dude]

The easiest way would be to measure the voltage drop across the existing cathode resistors and calculate current from that. Remember that the cathode resistor is shared by two tubes, so divide your measurement by 2. If there is adjusting to be done, you would change the cathode resistor values, but lets start by measuring first and see if adjustment is even necessary. Also, it's two separate amps, so there will be two separate bias checks.

[gtrplayr1976]

The easiest way would be to measure the voltage drop across the existing cathode resistors and calculate current from that. Remember that the cathode resistor is shared by two tubes, so divide your measurement by 2. If there is adjusting to be done, you would change the cathode resistor values, but lets start by measuring first and see if adjustment is even necessary. Also, it's two separate amps, so there will be two separate bias checks.

Thanks Dude. That's what I'll do. Waiting on caps to recap it first. Are 7-10 watt cathode resistors necessary ,or overkill ?

[erstevies]

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

I just bought the Gretsch 6169 Fury head (not the Chet version, the regular 6169) I can't for the life of me find a proper speaker cable for it. Someone I know is selling the Chet Atkins 2x12 cabinet from this era that needs a trs (double tipped) cable to connect. I want to get the cabinet for my head but obviously need to find some way to get a proper cable.

Any leads on how to get proper TRS stereo speaker cable with one jack on both ends? It doesn't seem to exist in speaker cable form. Would it be easier to re route the jacks on the head and cabinet to be two mono jacks or something?

The search for this cable has left me feeling pretty stupid and confused. Would appreciate any insight or leads on how to get one as I would like to run this head properly