Peavey Mace 320T Screen Resistors

[TomCarlos]

Hello Forum Members...

I posted this topic in other Forum Groups but never received a reply that helped me.

I just finished recapping a Peavey Mace 320T. I replaced some resistors as well. The amp is working fine now.

My Question: Why-oh-why did Peavey use only two 100 ohm screen resistors for three tubes? It's as if one of the tubes is not protected and seeing the full screen voltage. One 6L6 Screen goes directly to the OT. The second 6L6 has a 100 ohm screen resistor that connects to the Screen of the first tube. The third tube has a 100 ohm from the OT to the Screen. What's up with this? Why not have a 100 ohm from the OT to each screen? Or maybe use a 470 on each screen as done with Fender amps?

The 6L6 tubes are the originals. But they are nowhere near matched.  I am wondering if that is how they always were or if some have drifted because of the screen resistor setup?  I just don't know.

I have seen some videos on Peavey amps, mainly from Psionic Audio where Lyle suggests changing out the 100 shared screen resistors and using a 1K on each screen. I hate to think about altering a design and I am sure the amp will continue to work. But for the life of me, this is weird.

After 50 years, the screen resistors are still within specs, even the 47K grid resistors. But I am asking out of curiosity!

Thanks in advance, Tom

[J M Fahey]

My Question: Why-oh-why did Peavey use only two 100 ohm screen resistors for three tubes?

Every cent counts.
1 cent saved 1000000 times means TEN-THOUSAND-DOLLARS!!!!! 

It's as if one of the tubes is not protected and seeing the full screen voltage. One 6L6 Screen goes directly to the OT. The second 6L6 has a 100 ohm screen resistor that connects to the Screen of the first tube. The third tube has a 100 ohm from the OT to the Screen. What's up with this? Why not have a 100 ohm from the OT to each screen? Or maybe use a 470 on each screen as done with Fender amps?

WAY back then tubes were very good and consistent and needed minimal protection.
Notice that contrary to 99.99% of schematics they specify Tube BRAND (RCA).
Just add the 1k 5W screen resistors plus fresh tubes.

The 6L6 tubes are the originals. But they are nowhere near matched.  I am wondering if that is how they always were or if some have drifted because of the screen resistor setup?  I just don't know.

I have seen some videos on Peavey amps, mainly from Psionic Audio where Lyle suggests changing out the 100 shared screen resistors and using a 1K on each screen. I hate to think about altering a design and I am sure the amp will continue to work. But for the life of me, this is weird.

After 50 years, the screen resistors are still within specs, even the 47K grid resistors. But I am asking out of curiosity!

Those tubes are 50 years worn abused.
Update amp properly.

[TomCarlos]

Just add the 1k 5W screen resistors plus fresh tubes.

Thank you Juan...