E,P, and,U valve heater, id.

[Amie]

Hi.

I'm sure this has come up as a topic before, and I did the search thing but didn't find anything.

I'm doing some experiments using TV/Radio miniature commodity valves, they are mostly used "pulls", and have mostly lost their markings.

I'm quite good at identification regards the internal structure, for example I can tell the difference between a PCC88, and an 89, but, is there an easy way to work out if the example has an E, P, or U, heater. U isn't too difficult, But if the valve is something like say, an *CC85 then it's not so obvious.

Thanks,
Amie.

[ppppenguin]

Apply 6.3V from a bench PSU and measure the current. If the current corresponds with the data sheet for the E type, then it's right first time. Otherwise wind up the PSU to the heater voltage for the P type. If the current is 300mA then you know it's a P type. If the current is still low then it must be a U type. To prove this, wind up to the U type heater voltage and check that the current is 100mA.

Doesn't matter if you use DC or AC but DC from a bench PSU is more convenient.

If you suspect it's an odd heater current (C for 200mA, H for 150mA etc) then you need to take more care. Not many in B9A/B7G bases.

Also beware of battery valves. Applying 6.3V to a D type valve will usually blow the filament.

[Old Sparky]

Correct me if I'm wrong but weren't (almost) all battery valves B7g types?

[Mike Watterson]

NO. Battery valves for 1.4V at least:
Edge Connect (P8A), Octal (K8A), Mazda Octal (K8B), German Y8, Rimlock, B7G, subminiature B8D (pins or left long as wires), subminature crimp outside (often 5 wires or cut for sockets), and various subminiature Russian tyes and USA 8 pin Loctal B8G.
A few subminiature are 0.65V and some battery valves have a centre tap for series 50mA or 25mA, or parallel 1.4V.

Note that 1.5V LT radios are really nominal 1.4V and recommended for 1.35V off a mains PSU. Many "6.3V" types originated with 3 x Lead Acid car battery, often with a vibrator for HT. Such a battery is closer to a nominal 7V on charge, hence USA "7" series.

The 2V valves were never intended to be connected to a cell on charge. Same with the 4V and 6V variants of same designs that went out of popularity when filament currents got lower in 1928 to 1934. By 1935 there may have only been 2V battery types. The 1.4V type first came out in 1938 as Octal / Loctal Sylvania and the similar filament current and spec RCA B7G came in late 1939/1940, plenty of portables and personal sets in USA in 1941 before Pearl harbour. UK used P8A, Mazda Octal and regular Octal versions of the 1.4 Sylvania tubes from 1939 to 1950 and even 2V tubes for rural table models till 1950. The RCA B7G first in the Romac in UK in 1946 and not widely in UK till 1947.
Germany used Telefunken Y8 1.3V from about 1941 till about 1950 (parallel only as various currents and NiCd as LT regulator on mains) as well as regular 1.4V valves from 1945.
Philips did the most B8A rimlock 1.4V types and developed the 25mA B7G in about 1953.
Some battery valves are nickel filament and some tungsten.

There are loads of 6.3V B7G, particularly in USA, Commerical and Military gear. The USA also used B7G 115V heater rectifiers for battery/mains sets.
Also the 150mA (H) is rare in UK but common in USA and in USA B7G, Loctals and Octals.

The 2V battery types in at least 4 pin (maybe 3 kinds), (some pentodes, 5th side pin, TC or 5th pin), 6 pin (US & UK), Old British 7 pin and Octal.

[Mike Watterson]

The DK40 (rimlock) was used for SW sets as the DK91 / 1R5 was poor at HF. Later replaced by DK92. I've one Pye with all B7G except for frequency changer, DK40. The 25mA DK96 was also poor at HF, and the 25mA + 25mA DL96 limited in power compared to 50ma + 50mA DL94, hence "better" battery sets after DK96 and DL96 would use DK92 for extended HF or DL94 for x2 volume. I've one Philips set post D*96 series that uses 2 x DL94 and a DK92. A later model added DM70/DM71 magic eye by replacing ONE of the two DAF92 valves. One was detector/preamp and other for phase splitter. It uses EIGHT "D" cells for LT and 2 x 45V HT, but on mains the HT on the DL94 is at the Philips absolute max, for a massive volume. Also usually uses multiple loop aerials disgused as beading in series or parallel for SW (no telescopic) as well as the LW & MW internal loops.

The USA used the 1LC6 (1.4 loctal) for SW battery sets, later replaced by the B7G 1L6, even in many USA MW sets. Very few USA models used 25mA battery valves, except the sub-miniature valve pocket sized battery valve sets on 45V or 67V pack like a long PP3. Those valves only used for hearing aids in UK. Some test gear weirdly used them.
The DK92 is different construction and looks like different pinout to the 1L6. A direct swap will work on MW. Higher frequency bands need re-aligned as the capacitances are all different.

There is a B7G mains 6.3V Triode-Hexode, that manages by using one heater pin also for the cathode.

Some Noval valves are 12.6V only heaters without a centrer tap. Some 6.3V types (with and without centre tapped 12.6V) are also designed for 300mA series mode.
The USA used 150mA rather than 100mA (after both switched from 200mA) for series as they often had more valves and thus a 100mA series chain would exceed the nominal USA supply voltage.

[Mike Watterson]

You can also measure filament / heater resistance. In general when cold about half what the voltage & current suggests. You can compare with known valves of the same type.
Some valves (Mullard / Philips) have a separate etched part code. Different factories may have a different code. Apart from dismantling and measuring every part, and testing at same rating, this is also how we know that ECH81 = ECH83, just a different datasheet and part number. Absolutely proven to be same valve.

[Amie]

Thanks Jeffrey, Mike.

I've now done quite a few, identifying the type then finding out which is what with the bench PSU, then measuring the cold  resistance and comparing the others from those.

I didn't realize that there was even a UF80 made....


Amie

[ppppenguin]

Amie, I'm sure you already know this but there are a number of E series valves that have 300mA heaters. Hence they are used in both series and parallel designs. The EF80, EB91 and ECC81/2/3 are examples. The ECC81/2/3 are unusual in having an extra heater pin so they can be used as 6.3V 300mA or 12.6V 150mA.

There are also a few 300mA valves where the heater voltage is less than 6.3V. For example the PC97 UHF tuner valve has a 4.5V heater. You're unlikely to damage one by connecting 6.3V to it for a short period.

[Refugee]

Also the PC900 at 4 volts. It is also a UHF tuner valve.