Supro 1622RT schematic

[Helmholtz]

Correct, that is 45ma per tube... still insanely hot for these tubes which are 12W rating. The discrepancy with your calculation and my other one on the OT primaries is most likely due to tolerance in my meter's measurement of the primary resistance and or voltage across the primary.

I don't believe in that much tolerance. Please answer my questions.

[lowell]

Oh right I missed your question. I checked Rk upon initial inspection, 208ohms.

[Helmholtz]

https://www.tubesandmore.com/sites/d...les/6973eh.pdf

apologies, 6973

Thanks.
What's your B+, your heater and actual line voltages?
What's the actual in-circuit DCR between cathodes and ground (leaving the cap in place)?

The tube datasheet suggests a cathode current of 43mA with a B+ of 300V. Cathode biased amps are often biased at around 100%.

BTW, when measuring OT primary DCR, short the secondary to avoid false readings caused by large inductance.

[lowell]

Thanks.
What's your B+, your heater and actual line voltages?
What's the actual in-circuit DCR between cathodes and ground (leaving the cap in place)?

The tube datasheet suggests a cathode current of 46mA with a B+ of 300V. Cathode biased amps are often biased at around 100%.

BTW, when measuring OT primary DCR, short the secondary to avoid false readings caused by large inductance.

Great tip on measuring DCR of the transformer, thank you.

B+ is 345v

Actual DCR with cap in parallel is what I read - 208ohms

I'll report back on line and filament voltages

[lowell]

Here's where we're at

Filaments - 6.6vac
Line - 122vac

I did just notice that one of the dropping resistors feeding the PI (phase inverter) PSU node, which is 12k, looks very slightly discolored like it overheated. Being that this is the node after the Screen Grid supply node in the PSU, I don't see how it would be related here.

[Helmholtz]

Here's where we're at

Filaments - 6.6vac
Line - 122vac

I did just notice that one of the dropping resistors feeding the PI (phase inverter) PSU node, which is 12k, looks very slightly discolored like it overheated. Being that this is the node after the Screen Grid supply node in the PSU, I don't see how it would be related here.

Ok, measure the 12k resistor value and replace if more than 20% off.

Apart from that I would increase the cathode resistor to 330R to prevent overdissipation.

[g1]

How does running a 12W tube at 14W make it red-plate?
Maybe you do have oscillation. Have you tried grounding the grids?

[lowell]

How does running a 12W tube at 14W make it red-plate?
Maybe you do have oscillation. Have you tried grounding the grids?

I did try grounding the grids... didn't help. I'll try a larger Rk I guess. We shall see!

[lowell]

Okay ended up with a larger Rk to make it act right

[mihaila]

hi, I have a different problem with my Tremoverb 1622, low volume but not distorted, no red plating

my amp tech needs a schematic, did you manage to find one? or any tips I can tell him?

many thanks,
Mihai