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In Reply to: RE: The MV75A had an Achilles' Heel posted by DustyC on January 9, 2025 at 06:54:48:
The MV 75 had 590 vdc on the plates and if you used the LED bias, the idle current was 75 ma, which equals a dissapation of 44.25 watts of heat! The max rating for the 6550 is 35 watts for the plate. Is it any wonder tubes did not last or fail completely?
The solution was to change the cathode resistor from 20 ohms to 28 ohms and you can use the LED bias and not over dissapate the tube rating.
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Follow Ups
- CJ ignored the tube manual - garymuffley 12:29:27 01/09/25 (2)
- "Is it any wonder tubes did not last or fail completely?" - AbeCollins 12:21:54 01/11/25 (1)
- RE: "Is it any wonder tubes did not last or fail completely?" - DustyC 19:21:14 01/14/25 (0)
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