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It is a widespread misunderstanding that PCC88 has 7 volt heaters.
The correct is 7,6 volt, which is 20% higher than ECC88 (6DJ8), E188CC etc. which some substitute it with. Is it other consequences than shorter heater life?
Edits: 03/10/15 03/10/15 03/10/15Follow Ups:
You will reduce the maximum available cathode current by running the heater with less voltage than it calls for.
lower heater voltage=longer filament life, according to US MIL studies.
0.8 x 7.6=6.08, so a 6.3 volt filament is slightly less than 20 %.
Filament voltage should be within 5% from nominal. Too low voltage means cathode stripping = shorter tube life. Too high voltage means shorter heater life = shorter tube life.
The heater is rated for series string (rather than parallel) operation so is usually referred to as a 300mA type , hence the 'P' prefix . I do not think using at 6.3V is a good idea . I once built a clone of Allen Wright's PP1C , this could take E88CC or PCC88 . It used DC heaters with an LM317 current source set to 300mA .
Al
I have never opened my EAR912 nor do I have the schematic, but then it should be ok to substitute ALL 5 PPC88 with ECC88/6DJ8 or other derivates which draw 300 mA. I was thinking of replacing them with E188CC, but they draw 335 mA and it is no good to starve them with 300 mA. Wonder how to get a schematic.
Johnny
How are the heaters configured ? Suggest you email EAR
Al
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