Hot Rod Deluxe III - looking to make 2 bias check points

[Iplayloud]

I have a pair of old GE 6L6 tubes that I dropped in the amp, but my infrared temp meter shows a huge difference between each, making me think they're really not balanced. To make sure my meter doesn't read the glowing heaters I shut the amp off and measure after a few seconds.

The Hot Rod Deluxe has a 1 ohm cathode resistor to ground, and the bias checkpoint measures both sides. I'm thinking of simply separating the path to ground of each 6L6 and putting another 1 ohm resistor.

I'm just worried about the diode in parallell with the 1 ohm cathode resistor. That diode is called CR3 on earlyer versions, and D3 on version III. On my amp it's a 1N4006. Should I put a 1N4006 diode in parallell with both 1 ohm resistors? (each sides)

Next idea would be to add a bias balance pot like Silverface Fenders.

[glebert]

Personally if I am not getting hum I don't worry about tube matching/balance. I think it is easier to just get a bias probe set and measure the current if you are worried about it. But of course everyone has different ways to approach things.

[Helmholtz]

I'm just worried about the diode in parallell with the 1 ohm cathode resistor.

Yes, give each side a 1R resistor with own bypass diode.

[Leo_Gnardo]

I have a pair of old GE 6L6 tubes that I dropped in the amp, but my infrared temp meter shows a huge difference between each, making me think they're really not balanced. To make sure my meter doesn't read the glowing heaters I shut the amp off and measure after a few seconds.

While it IS perfectly possible your venerable GE's aren't well matched, it's also possible there's a drifted or open-circuit screen grid resistor in one of the output tube circuits. Make sure both measure 470 ohms or thereabouts. Sometimes they fail and don't look damaged, only your ohm meter will know. This kind of failure suppresses current through the tube. If the screen grid R's are OK, I'd select other output tubes that have a better chance of working together rather than squeeze in a balance control.

And I DO approve your use of temperature readings on those tubes. I got a one of those cheap ($25 at the time) infra red laser thermometers nearly 20 years ago from Parts Express. It's come in handy hundreds of times. Perfect for revealing output tubes that are running hot or cool, especially which ones in a set of 4 or 6 or more aren't really behaving. I don't bother switching the amp off. After a warmup, I expect the heat contributed by each filament will be nearly the same, so differences in temp are related to differing plate/cathode currents.

[g1]

To check for circuit issues like Leo mentioned, you could also swap the tubes around and recheck with your temperature probe.
Another option is checking at the test point with only 1 power tube at a time (using same socket for both). This will not give a correct bias reading, but will show you any gross mismatch of the power tubes.