Can anyone identify these valves?

[HamishBoxer]

Number 3 I also will go for PL36

[Station X]

Thanks for your answers everyone.

I'll go for PL36, 6J7G and EF37A.

http://www.r-type.org/exhib/aaa1338.htm

I'll try to find something more challenging for you to identify!

Most of the valves in this box of "pulls" seem to be 50's TV, or American military types.

[Station X]

Here's number 6.

IDENTIFIED AS A 6K25.

The green stuff is probably algae!

[ms660]

Number 6, 6K25....long shot?

Lawrence.

[Station X]

Could be. Now I look more closely I can see evidence of silver paint around the top of the brown plastic base.

[Station X]

There's low resistance between pins 2 and 7 suggesting they're the heater pins. Also very low resistance from pin 1 to the grey paint. All consistent with it being a 6K25.

[ms660]

6K25 heater current is given as .95A, I reckon cold resistance would be 1 ohm or a bit lower....might be an indication? Could always rig it up lash up style and see if there's a pretty glow..

Lawrence.

[Station X]

I have an AVO CT160, so I didn't have to use a lash up. I did however have to read up on how thyratrons work and how they are tested.

The AVO manual says not to attempt inter-electrode short tests, as the AVO's 150V test voltage may damage the valve, so I didn't do them. Heater continuity was OK and with no HT applied the heater glowed nicely.

The test technique is to connect a 2k resistor in series with the anode, apply anode voltage (in this case 100V), then reduce the negative grid voltage until the valve strikes and starts to draw current. I had to settle for a 2.2k resistor, as I didn't have a 2k one in a suitable power rating.

The valve struck at -3.8V and the anode current shot up from zero to 15mA. Reducing the grid voltage to zero resulted in an anode current of 24mA (spec is 30mA).

The purple glow was there alright, but only just visible in a darkened room.

Well done Lawrence!

I'll spray the valve with zinc rich primer.

[ms660]

Thanks Graham, my street cred has been renewed.

I used the Rtype org site for pics and went through the elimination process for triodes (and diode triodes just incase) That just left the 6K25 as a contender insofar that it was the only GT metalized triode valve with no top cap and with a full complement of IO pins, doing a quick height to width ratio of the valve in your photo also more or less fitted the ratio derived from the dimensions given on Rtype org.

Lawrence.

[Station X]

Here's number 7.

It says "MADE IN HOLLAND", so I expect it's a Mullard.

INDENTIFIED AS AN EBL21.

[ms660]

Number 7, UBL21?

Lawrence.

[TonyDuell]

I was going to say EBL21 for that one. Much the same valve with a different heater, and probably impossible to tell apart without making electrical measurements on the heater.

[m0cemdave]

It should be possible to identify which it is from the Philips code stamped on the metal ring.

It looks like:
631
5-D
which doesn't quite fit the usual code format.

Can you confirm the characters?

Maybe one of the forum's Philips experts will be able to make sense of them.

[ms660]

This chap came to the same conclusion:

http://www.gloeidraad.nl/radioforum/index.php?id=231116

Lawrence.

[ms660]

According to this, 631 was one of the factory codes used for the EBL21:

http://www.hupse.eu/radio/tubes/EBL21.htm

Measuring the heaters (if intact) should confirm.

Lawrence.

[Station X]

Looking under a magnifier it's definitely 631 5-D.

I'll endeavour to test it tomorrow.

Originally Posted by m0cemdave

It should be possible to identify which it is from the Philips code stamped on the metal ring.

It looks like:
631
5-D
which doesn't quite fit the usual code format.

Can you confirm the characters?

Maybe one of the forum's Philips experts will be able to make sense of them.

[Maarten]

Originally Posted by Station X

Here's number 7.

It says "MADE IN HOLLAND", so I expect it's a Mullard.

631 is the old production code number for EBL21. The production code for the otherwise iidentical looking UBL21 was 550. I'm not sure on the date format used with those old codes so I can't quite explain 5-D.

[Station X]

Number 8. The last of the large unidentified valves.

The heater is between pins 2 and 7. No other pins show continuity to each other or to the heater.

Height not including the pins is about 67mm.

I'm not expecting an answer!

[julie_m]

If you have two adjustable power supplies, one good for a few tens of volts, you could warm up the heater and check for diode action between pairs of pins (use a high-brightness LED with a resistor to limit the current to 1 mA, as grids don't really like being used as anodes, with the possible exception of the frequency changer in a battery set). Then, for each cathode and possible anode, see if applying a negative voltage to any of the other pins cuts it off. You can work out by a process of elimination which pin is the anode and which are grids (and their order) and possibly separate diode anodes.

[turretslug]

Number 8 possibly 6N7? (My initial reaction was good ol' 6V6, there are several here all of c.67mm height but pin 6 is not fitted on these. Then I thought, there're are few 6N7 somewhere also, sure enough these are also around 67mm high and the twin-triode (commoned cathode on pin 8 but pin 1 connected to steel can) nature means all 8 pins are present). Heater current of 0.8A at 6.3V would be another pointer, though there might be one or two others that fit the bill.