Unidentifiable Valves

[BrianAllen]

Good evening all,

I have quite a few radio valves that have the identifying letters and numbers missing, so my question is, are they now of no use as they are unidentifiable?

Thank you.

Brian

[GrimJosef]

No. There are various ways of identifying the pin connections, which will narrow down the possible types that they are. There are also ways of helping to make nominally 'rubbed out' labelling a bit more visible (I find the best is very bright sunlight and a magnifying glass).

Cheers,

GJ

[BrianAllen]

Thank you GJ, will give it a try when the sun comes out!!

In the meantime I will sort them by their pin connections.

Brian

[GrimJosef]

A resistance check will tell you which pins are connected to one another,. One pair of these (there may only be one pair) will be the heater pins. A capacitance check between these and the other pins should identify the cathode. You may actually be able to see which electrodes are connected to which pins (hard to do if the base is a glued-on bakelite one though).

Cheers,

GJ

[McMurdo]

If you can see inside the valve then with a bit of experience you can usually recognise the electrode structure. A power supply with current readout (and limiting) will help with the heater ratings.
My biggest stumbling block to all this is obscured glass, either by metallizing or that smoky grey coating used on older valves.
My biggest resource is r-type.org, as they have good closeups of most common valves and a great search engine.

You could always post closeups of the innards on here!

[BrianAllen]

Good thinking Kevin and GJ,

I have actually been on the r-type website and yes, amazing close up pics of the valves; will certainly give it a try and try and identify the valves I have.

Brian

[chriswood1900]

Brian
Another thing to look for are codes etched into the glass near the base, particularly on valves from Philips group factories , (Mullard Tungstram, Philips, etc).
A guide to the codes is here:-
https://frank.pocnet.net/other/Phili...deListABv8.pdf'

[BrianAllen]

Thank you Chris; very interesting info.

Regards,

Brian

[barretter]

Originally Posted by chriswood1900

Brian
Another thing to look for are codes etched into the glass near the base, particularly on valves from Philips group factories , (Mullard Tungstram, Philips, etc).
A guide to the codes is here:-
https://frank.pocnet.net/other/Phili...deListABv8.pdf'

They're not etched but printed with a fairly indelible ink. Some Brimar valves also have codes which can be used to identify the valves if the main number has worn off.

[cathoderay57]

Occasionally you can breathe on the glass and providing it is cold enough sometimes the previous lettering can be seen. Jerry

[Buzby123]

One of those little LED torches I find very useful when trying to read rubbed-off print.

[Maarten]

Some of the Philips codes aren't in that document (v8, there's a v10 floating around on the net somewhere but it still lacks the professional tube range and the coding system that was used from the 1930's to the late 1940's), but please post here in case of doubt.

[Robert Gribnau]

A link to revision 10 from 2011: http://www.r-type.org/pdfs/ref4110.pdf