ECC88 and PCC88 filament voltages - diyAudio
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Old 31st March 2004, 07:30 PM   #1
sith is offline sith  Croatia
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Default ECC88 and PCC88 filament voltages

Hi folks

I have some ECC88 and some PCC88.Now, I know that filament voltage for ECC is 6.3V and for PCC is 7.6V.
What may happen if I use PCC on 6.3V Will it work?
Or ECC on 7.6V will it work or would it blow?
Secondary for filament is 18V 2.3A would it be wise to connect two valves in series and lower secondary voltage to 12.6V i.e. 15V?If so I plan to use 7812, is there a better solution?

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Old 31st March 2004, 10:07 PM   #2
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The PCC88 filament is designed voor series operation, with a current of 300mA.
The voltage is not referenced so just make sure the heater is working with a current close to the spec 300mA.

7.6V on an ECC is way to much, the internal heat can destroy the tube.
6.3V on a PCC can work if you meet the above specs.

Dick
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Old 31st March 2004, 10:36 PM   #3
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Hi,

Quote:
7.6V on an ECC is way to much, the internal heat can destroy the tube.
It won't destroy it, I sometimes use as much as 9 V to revive a tube, but it will exhaust in rapidly if you keep it at 7V+ for too long due to excessive emission.

For the PCC you could use a current regulator set at 300mA.

Hmmm, makes me wonder how they heated the PCCs in the Audio Innovations amps of yesteryore...?

Cheers,
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Old 1st April 2004, 09:18 AM   #4
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Hi

I utilize the following simple circuit to provide the correct
DC voltage to the filament of both ECC88 and
PCC88. In this way I can exchange the tube and they
will always receive the appropriate voltage.

Federico
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Old 1st April 2004, 08:45 PM   #5
sith is offline sith  Croatia
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thanx guys

Quote:
For the PCC you could use a current regulator set at 300mA.
OK, but how to make it?

And, how about this idea?

Quote:
Secondary for filament is 18V 2.3A would it be wise to connect two valves in series and lower secondary voltage to 12.6V i.e. 15V?If so I plan to use 7812, is there a better solution?
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Old 1st April 2004, 10:30 PM   #6
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Hi,

You could use a combination of voltage and current regulator like in this example:

Cheers,
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