Biasing Advice for 50CA10 - Luxman SQ38FD

thr33p4c

thr33p4c

AK Subscriber
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A Luxman SQ38FD Came across the bench.

I cannot seem to find any info on recommended bias setting for the 50CA10. Another tech installed some 10ohm resistors from Cathode to Ground. On initial measurements it looks like someone was aiming for around 30mA but this seemed a little low. I used the bias/balance pots in the output section to dial each tube into about 40mA across the cathode resistor. I could not even find the 50CA10 in the RCA Receiving Tube Manual.

Any advice would be greatly appreciated.
 
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Thank you so much Binary Mike!

So looks like 50mA each in push/pull correct?

At 100VAC input I am getting about 407V on the plates. The OPTs are 5K so it looks like they are running these pretty much at max on the spec sheet. Output Power on the spec sheets says 34W. I think at 40mA I'm running at roughly 45 - 50% of max plate dissipation. Can someone check me on this?

Grid Voltage -37V give or take depending on tube.

Is this too cool? These tubes are pretty rare so would rather play it safe. Sounds great at current setting.
 
at 50ma at 410v you're at 20.5w, you're only at 60% rated plate dissipation. Honestly I'd run at the datasheet settings, its relatively conservative.
 
All, thank you for the advice. I'm going to stick with the slightly lower setting to play it safe. Sounds really nice right here.
 
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