KEL 84 Tiode Undoing

[Dave Senior]

Hello

Its over a year since I used my KEL84 and I have made many cable changes since then. Today I replaced my 300BSE with the 84 and I am very surprised at how good it is - more punchy than the 300b. The 84 is configured as a power amp running in triode mode.

I can't remember how to change it back to UL mode. Can anyone help because I want to try experimenting again!

Regards
Dave

[jimangus]

Hi Dave,

it was a long time ago since i had my kel in that config.

The ultra linear wires go back to there original positions on the circuit board, pink red black grey. Labeled on the pcb.

There was something to do on pin9 and an additional 100k resistor but that bit i cant remember, perhaps joining pin 9 to a different pin with a resistor of that value.


The circuit diagram is still available here, this may help. http://http://www.world-designs.co.u...alog/kel84.pdf

Regards
Jim

[Richard]

Hi David

Yes I think all that will have been done to go triode will have been to disconnect the pink and grey OPTX tap wires, then connect pin 7 anode to pin 9 g2 via 100R resistor. So just reverse this following the original circuit, to re-instate UL, then check all voltages to be sure.

[Ianm2]

and then pentode wire it, trust me

[jimangus]

Originally Posted by Ianm2

and then pentode wire it, trust me

This is of course subjective.

To me ultra linear sounds best.

Worth a try though.

Jim