P-Series Valves, what to do with them?

[davegsm82]

Thank you everyone, I wasn't thinking of chucking them as I know they will eventually find a use and even possibly a value, but whether that's in my hands or my lifetime remains to be seen. Worst case scenario I guess I'll shuffle them off onto eBay or something.

I'm just taking stock of all the 'stuff' I have at the minute as it's becoming a 'hoard' quite rapidly, and I'm looking at valves I'll probably never use thinking what's the point in keeping them. Interesting info about the PC86/88, pretty sure I've got a good few of those, and PC900's.

Dave.

[ppppenguin]

According to my stock list I've 23 NOS PC900. Also 63 PC88 and 12 PC86, again NOS. Also some PC95 and PC97 though I've no idea where they were used.

The PL81/EL81 ought to make a good audio output bottle. Not as powerful as a PL519 but possibly useful.

[pwdrive]

The PC97 was a popular TV VHF tuner valve, the PC900 was used in TV VHF tuners as well, the PC86/88 were TV UHF tuner jobs.

Lawrence.

[Ed_Dinning]

Hi Gents, in most instance's a valve type with differing prefix letter will always use the same heater power (V*A), so it is quite easy to make a small auto transformer to act as a "voltage shifter".

As the power is low quite small transformers can be fitted under the chassis. They would also have a low turns count as the voltage is low.

Ed

[davegsm82]

Hi Gents, in most instance's a valve type with differing prefix letter will always use the same heater power (V*A), so it is quite easy to make a small auto transformer to act as a "voltage shifter".

As the power is low quite small transformers can be fitted under the chassis. They would also have a low turns count as the voltage is low.

Ed

Fixed valve heater power is one way I was going to try and ID unmarked valves, since you know that anything in a B9G socket will likely not be much more than 6W you could simply apply a fixed power for a given envelope height (PCC83 @ ~2W, PCL86 @ ~4W, PL84 @ ~4.5W, PL81 @ 6.3W for P-series examples) and see what voltage pops up on the pins, fixed power would come from a clever SMPSU with primary side power regulation.

Ed, your Auto-transformer idea is very good, I was thinking about making a valve base 'interceptor' plug and socket, breaking out the heater connections and running them to an AutoTX somewhere else, under the chassis or at the side of the set etc. What would be the cost for such a transformer? I guess only a few types would be needed to convert for common types (E-->PCL8x, E-->PCC8x, E-->PL84).

Dave.

[ppppenguin]

Dave, do you mean PCC83? The ECC83 can be used in 300mA series chains so there's no such thing as a PCC83 that I've ever heard of. Presumably given the context B9G is a typo for B9A.

Not sure about you constant pwoer idea. While it's probably true, it's a big hammer to crack a fairly small nut. Apart from a few small B7G triodes I think all P series valves need more than 6.3V heater. So easy enough to use a variable PSU and meters to see what's happening.

[peter scott]

Perhaps Dave means constant current since all the P series run on 200mA. You could design a high voltage supply that was limited to 200mA if you wanted flexibility to run different series configurations of valves.

Peter

[Terry]

Dave, if it has a B9G base, I'll bet on it being an EF50. (I only bet on certainties!)

If, on the other hand, it has a B9A base, and came from any factory in the Philips empire, identification is easy!

Just above the base you should see two rows of characters etched into the glass. The first identifies the valve type number and the second tells you the place and date it was manufactured - for example, B3C4 tells you that it was manufactured at Mullard's Blackburn factory in the 4th week of March, 1963.

To translate the first row of characters into a familiar type number you will need to consult this handy document.

Now you will know everything about your valve there is to know except the name of the girl who assembled it!

[Nick]

I'm active on a UK Audio builders & designers forum - they have a load of threads on peoples' projects - there is a current thread on a PCL86 single-ended ultra-linear monoblock design that one of our long-time members is designing...

PCL86 SE Ultralinear Monos

also

PCL86 Triode SE Spud Amp

The Other Not Ultralinear PCL86 Monos

[pwdrive]

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

Lawrence.

Anyone? Or am I reading the specs/curves wrong?

Lawrence.