P-Series Valves, what to do with them?

[ppppenguin]

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

I'm sure that 200mA is a typo and that Peter knows that P series are 300mA.

There are some 200mA and even 150mA valves though they are less common. I think they are C and H series respectively in the Pro-Electron system. Some early 1950s TV used a wonderful mixture of 100mA, 200mA and 300mA valves leading to a somewhat intricate heater chain.

Am I right in thinking that there were enough P series (and 300mA E series) valves in a Philips G6 colour set for it to hardly need a dropper at all.

[pwdrive]

Having looked at the data sheets (Philips) for the PL84, UL84 and the EL84 I've come to the conclusion (heaters aside) that characteristics wise the PL84 and the UL84 are the same but the EL84 is different.

Lawrence.

[BusyBee]

I have a small number of P series valves, but seldom use any. I do however use DC supplies for all of the circuits I build. As such I don't have too much of an issue with different voltages within reasonable limits. It's maybe just having a spare to hand which occupies my thoughts more. I can see problems with replacing E series with P, but, except for keeping things original, it wouldn't bee too much of an issue.

Tracy

[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

I'm sure that 200mA is a typo and that Peter knows that P series are 300mA.

Oops! Not a typo, just poor memory. I knew it was something like that.

Peter

[Refugee]

There are some awkward bottles out there.
How about a rectifier found lurking in a radio with a dropper mains lead?
http://www.r-type.org/exhib/aaa0648.htm
And then the output valve.
http://www.r-type.org/exhib/aaa0151.htm
The set actually has a 160ma heater chain.

[boater sam]

With buck/boost modules available from China for 99p and diodes, 1N4007s for pennies a hundred, changing the heater voltage to use "P" valves is a cinch. 
Even arranging a 300mA chain and converting all the valves fro "E" to "P" would be possible, DC heater supply an advantage too. 
I've run "P" valves with heater voltages a little bit over 6.3v on the 6.3v supplies and they seem to work OK.
Sam.

[BusyBee]

A couple of weeks ago I put together a little signal generator for a specific purpose. In it I used a 1j29b valve at 50V, using boost modules for HT and a buck for the 1.25V supply I use for heater supply (further dropped by heater choke), all powered via the 9V transformer output I used with the semiconductor side. The project, in some ways, was an academic exercise as I used an Arduino Nano for frequency generation plus transistors so was a hybrid in a big way, but did usefully confirm several things and does work for what I designed it for.

Tracy

[pwdrive]

Trying to delete  

Lawrence.

[BusyBee]

Just to add to my previous post. Obviously there are issues with DC power when regulating for heaters.The biggest issue I have found is waste of power and heat when dropping voltage. The shunt regulator is far more efficient and there is little or no heat to deal with.

Tracy

[Geordie McBoyne]

In the UK the PL84 power pentode is known for it's role as the frame output valve in TV receivers equipped with 110degree CRTs. In fact the PL84 was introduced in 1956 three years before the introduction of the 110degree CRT into Europe and the UK. Philips used two PL84s in a transformerless sound output stage in several continental TV sets.
From r-type.org: http://www.r-type.org/articles/art-146.htm
Heater voltage and current apart the characteristics of the PL84 are similar to the EL86.

The Philips K4 colour TV set also has a transformerless sound output stage. In this receiver the valves employed are a PCL86 and a PCL85

designed as a video output valve the PCL84 can be considered suitable as an audio output valve. Sobell and GEC used the PCL84 in the sound output stage in many TV receivers.

Philips used the EL81 in an audio amplifier. PL81 is becoming scare so best used for it's prime purpose as a television line output valve.

Geordie McBoyne.