Pcc88

[leo529]

hi, anyone know what is the heater voltage of this tube? i searched in the net, some datasheet said its 7V, and some said its 7.6V.

[Pjotr]

My good old Philips databook says 7.6V / 300 mA

[fdegrove]

Hi,

My good old Philips databook says 7.6V / 300 mA

My good old Philips databooks say 7V/300mA and another Philips databook says 7.6V/300mA.

The important part, IMO, is the 300 mA since it was designed for series heating.

If I'd use a single tube like this I'd use both voltage and current regulation on it, if I'd get picky.

Cheers,

[dhaen]

Hi,

How long do these things last at audio-frequency?
I remember them as UHF RF amplifiers, only lasting about a year.

Cheers,

[fdegrove]

Hi,

I remember them as UHF RF amplifiers, only lasting about a year.

Most owners of gear using this type of valve tend to replace them every 18 months.

In some so called high-end gear they are often dead after a year and even less...too high heater voltage, gives you a tad more detail for a while, too much of a twisted application...all of that makes sure that the pundit is sent to the till paying through the nose for a matched pair of candles.

Sorry to be sarcastic, my ECC88s haven't been replaced once in 20 years and they still measure 100% on the testers.
Same goes for all my tubes bar the 6080s...well those are the workhorses anyway.

Cheers,

[Pjotr]

The Philips data book here is the 1967 edition. The RCA Tube Handbook from 1957 also states 7V.

But you are right Frank, tubes designed for series connection (P types and U types) are best powered by constant current.

E types designed for constant voltage heater power certainly not, the heater of E types draw virtually a constant current by themselves at varying heater voltages.

Cheers

[bournville]

Interesting about the heaters - my Brimar manual says 7.6 volts but both Mullard and Tungsram say 7 volts...

I once read an article in an old radio mag which made great claims for the PCC88 as a small pp output stage. With fixed bias of -6v and a 200v on the anodes, output of 1.5w was claimed, and at its maximum ratings, with fixed bias of -5v and 210v on the anodes, output was supposed to be about 2.5w. The output tranny had a 10k anode to anode impedence. If I remember rightly the article warned of not exceeding the valve's limitations, or it deteriorates very quickly.

I saw this in an old Practical Wireless mag from about 1967-8, but I cannot remember the exact issue...if I find it out I'll post the reference.

[Brett]

Originally posted by fdegrove
If I'd use a single tube like this I'd use both voltage and current regulation on it, if I'd get picky.

I do this for almost everything now. I picked up a ton of LM317 and LT1083 for dirt so I do a voltage then current reg setup. The tubes come on slower and they're always set at just the right voltage. I haven't used series string tubes in a while, but I'd probably do the same, with the current as the set item.

Using this configuration on DHT fils is indistinguishable to my ears from AC, except without the hum. Use the LT's though.

[leo529]

thanks all, so the best way to heat up my pcc88 is using a 300mA current sourse, am i right?

[fdegrove]

Hi,

so the best way to heat up my pcc88 is using a 300mA current sourse, am i right?

Yes, stay around 7V 300 mA and you'll be fine.

Cheers,