Check the cathode resistor.

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In Reply to: red hot plates! help! posted by bobsmog on March 20, 2002 at 20:02:47:

They're not foolproof; they can change value, or fail short. There's nothing in parallel with a cathode resistor, so you can check with a DVM with the set unplugged, and compare its resistance with the color bands and the resistance of the other channel (which is not glowing; right?).
Another check is to power up on the bench, and hold your hot probe on the suspect cathode(s) - it (they) should hold at about 20Vdc in operation, give or take.
Another possibility; is there a capacitor bypass for this resistor? Check its DC resistance (should start low, and climb to open).
This is a fairly simple problem, at a glance. The cathode resistor, or its bypass cap has to be at fault. I think.
You can post me at:
poinxie 'at' yahoo.com (addy cleverly disguised)
if none of this works.
Poinz

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Follow Ups Full Thread

Topic - red hot plates! help! - bobsmog 20:02:47 03/20/02 (4)

assuming that the cathode resistor on your right-channel - Quest 22:31:11 03/20/02 (1)

Yeah, didn't think of that. - Poindexter 10:35:04 03/21/02 (0)

Check the cathode resistor. - Poindexter 22:26:23 03/20/02 (0)

Post in tubes! Have you checked the bias? - Tromatic 20:26:06 03/20/02 (0)

Follow Ups

Check the cathode resistor. - Poindexter 22:26:23 03/20/02 (0)

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