P-Series Valves, what to do with them?

[davegsm82]

As per the title, I'm wondering what, if anything, can be done with old TV-pulls, almost always usually P-series valves?

I rarely touch much vintage gear at the moment due to the lack of work area, but I decided to filter my glass into a few major categories, E, P and U series heaters, 'Large, odd and interesting' and 'Special' just to try and get to some sort of organisation.

It boils down to at least 3 large shoe-boxes of P-series (PCLxx PCCxx PLxx etc etc), one box of which is almost entirely new and boxed valves. I'm loathed to get rid of them but I really can't see me ever having a use for them because of the odd heater requirements and the fact I don't really have an interest in TV's (other than owning a TV22).

Is there any point in keeping them? is there a market for them?

Dave.

[ppppenguin]

Just need to convince the audiophools that PC86, PCC84 etc have magical, mystical properties. Then we're all rich

And just what kind of fish has ppppenguin been smoking?

[Refugee]

If you are making something home brew the heaters can be run from a transformer of an odd less useful voltage.
I have looked into this several times.
Old printers used to have a 40V transformer that could run heaters in series and HT via a tripler for a small amplifier.

[ppppenguin]

When using P series valves please be aware that some (but not all) similarly numbered valves E and U series have different specs as well as different heater voltages. For example PL84 is not the same as EL84.

[Murphyv310]

Hi.
P series valves are very useful and many have ideal characteristics for both Audio and RF applications. PL82's and PL84 are good audio valves and contrary to what Jeffrey says the PL84 and the EL84 bar the differing heater characteristics are the same valve. Although they seem different the PL84 have de-rated characteristics for AC/DC TV applications where HT of 250-300v is not available so the specs in the books are for the lower HT not the higher values, misleading but perfect common sense. Do your own load lines etc and you'll see it performs just like the EL84, see here: http://www.r-type.org/exhib/aaa0371.htm and can be run at the HT the EL84 is rated at, In fact I tried a PL84 in another Mullard 3-3 project some time ago and it was 100%
Don't throw out "P" valve pulls as they are the ones that will die a death before the likes of ECC81/2/3, EF86, EL84 which are still made. Valves like the ECL86 are now hard to find and expensive and again the PCL86 is the 300ma version of the hard to find ECL86 so again good reason the keep these valves.

[ppppenguin]

Trevor, thanks for correcting my misunderstanding.

Replacing rare E series valves is a valid use of P series valves. Obviously you've got to provide a separate heater supply, 13.3V in the case of the PCL86. This will often mean an extra transformer but if you've got a nice radio or gram with 1 or 2 faulty ECL86 the PCL86 replacement can be well worthwhile.

[Murphyv310]

Absolutely Jeffrey.
With some of the 12.6 volt heater valves all you need is another 6.3v heater transformer to put in series with the "P" valves heater connections you are replacing the "E" valves with, a little rewiring for the feed to those valves making sure the transformers are in the correct phase or you'll get zero heater volts. The same way can be used for higher heater voltage "P" valves with a transformer of the difference of the heater volts.

[ppppenguin]

There are a few P series valves with heater voltages below 6.3V. The PC86 and PC88 UHF tuner valves are both 3.8V.

[pwdrive]

PL84, UL84 v EL84.....What about triode connected?

Lawrence.

[Geordie McBoyne]

There has been some discussion about employing the PC900 frame grid TV RF amplifier valve as a preamplifier for magnetic phono cartridges. The valve has a vari-mu characteristic and this is said to render the valve unsuitable for large signal applications but considering the MM cartridge supplies only 10 to 30mV that shouldn't be a problem.
A discussion about using the valve here: https://www.diyaudio.com/forums/analog-l...tures.html
From the Radiomuseum: https://www.radiomuseum.org/tubes/tube_pc900.html

There has also been a discussion about using the PC900 as an audio preamplifier on the UKVRRR.

Geordie McBoyne.