Rectifier diode with three pins.

[FERNSEH]

Yesterday, I found this unusual valve. There's evidence it was made by Tungsram but I can't find the valve's type number.
Essentially a full wave rectifier having both sections wired in parallel.
This three pin valve will fit in a standard B4 socket.

DFWB.

[kalee20]

Wow!

I've never seen anything like that before...

[Silicon]

Is there a logo embossed or printed on the valve base?

B4 bases with only 3 pins were sometimes used for mercury vapour rectifiers (i.e. GU1).
However their internal structure is very different.

[ms660]

Tungsram V4200:

https://www.radiomuseum.org/tubes/tube_v4200.html

Lawrence

[Chrispy57]

Hi - certainly unusual, but you may need to reconsider this statement "Essentially a full wave rectifier having both sections wired in parallel."

Cheers
Chris

[ms660]

The Tungsram V4200 specs. are Vh 4V, Ih 2A, VAC max. 800V, I max. 120mA.

Lawrence.

[60136 Alcazar]

The Tungsram V495 from 1930 (400V/70mA directly heated 4 volt/1 amp) also had 3 pins and two anode structures. In fact Tungsram seems to have been fond of this arrangement as the APP4D was a single envelope containing two APP4A electrode structures strapped together, likewise the PP4018 was two PP2018 structures.

[Maarten]

Maybe they used this arrangement to obtain a higher current capability?

Originally Posted by Chrispy57

Hi - certainly unusual, but you may need to reconsider this statement "Essentially a full wave rectifier having both sections wired in parallel."

I'd say it is a bit ambiguous, but one of the ways it can be read seems to be correct, or am I missing something?

[Chrispy57]

Hi Maarten,
if it is indeed a V4200, as identified by Lawrence, the three pins are for an anode and both ends of the directly heated cathode, and it is described as a half-wave rectifier in the data sheet available here;- https://www.radiomuseum.org/tubes/tube_v4200.html

There is also the PV4200, which is a full wave rectifier having two anodes and a directly heated cathode, but this has 4 pins, data sheet here;- https://www.radiomuseum.org/tubes/tube_pv4200.html

Cheers
Chris

[60136 Alcazar]

The Tungsram arrangement used two electrode structures and two filaments/electron streams, but internally strapped anodes (and grids/cathodes as appropriate) and filaments internally connected in parallel (or in series for AC/DC types). And yes, this was to cater for an increased Ia rating. In the V4200 case, two anodes internally strapped together only need one external base pin connection, plus the two filament pins (with the two separate filaments paralleled within the envelope). So it is basically a twin diode internally configured as a half-wave rectifier.

[Oldmadham]

Three pins for a full wave rectifier wouldn't work, as the filament needs two pins to function.

[Herald1360]

Don't forget the 0Z4

OK so it actually has 5 pins fitted to its octal base but only three of them are active!

It's also rather noisy RF wise, as I found out the hard way in a home brew PSU for a R1155

[FERNSEH]

Introduced in the mid 1950s, except for it's heater voltage. the EY84 has similar characteristics as the V4200.
From the Radiomuseum: https://www.radiomuseum.org/tubes/tube_ey84.html
Slightly different, the Brimar R18.
https://www.radiomuseum.org/tubes/tube_r18_brimar.html

DFWB.

[Station X]

One post moved to a new thread here:-

https://www.vintage-radio.net/forum/...d.php?t=205696

[Oldmadham]

Originally Posted by FERNSEH

Yesterday, I found this unusual valve. There's evidence it was made by Tungsram but I can't find the valve's type number.
Essentially a full wave rectifier having both sections wired in parallel.
This three pin valve will fit in a standard B4 socket.

DFWB.

As the heater/filament needs two pins to work, you only have one pin left, so, at least functionally, it is a half wave rectifier using a directly heated cathode.

The valve manufacturer may be doing some "smart stuff" internally & reusing an already available stock structure from a full wave rectifier, but to the outside world it is a half wave rectifier.