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In Reply to: Will this work? Switching from 6.3 to 12.6 volts posted by DAK on June 11, 2017 at 16:52:21:
It's surprising to me that the Eico ST84 powers the 6X4 with the same transformer winding as used for several preamp tubes. There have been many reported failures of the 6X4 when used with its filament grounded. Apparently, the heater/cathode insulation isn't what it should be. This has been known for a long time - all the old Akai reel decks powered the 6X4 from a separate floating winding. I don't know if the 12X4 has the same issue, but it's worth considering. Eico might have used a particular brand or style of 6X4 that was more resistant to this failure mode.
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Follow Ups
- RE: Will this work? Switching from 6.3 to 12.6 volts - Triode_Kingdom 23:21:30 06/11/17 (5)
- Sorry, i was mistaken about the single 6.3vac tap - DAK 02:34:30 06/12/17 (4)
- Not according to the Eico schematic - Triode_Kingdom 11:11:51 06/12/17 (3)
- RE: Not according to the Eico schematic - DAK 11:49:35 06/12/17 (2)
- RE: Not according to the Eico schematic - Triode_Kingdom 13:10:47 06/12/17 (1)
- RE: Not according to the Eico schematic - DAK 14:55:00 06/12/17 (0)