Identify this valve please. (Identified as an 8D3.

[Bazz4CQJ]

No pictures as the entire B7G is silvered. The lettering is very poor; pretty sure it's a Brimar (and it is BVA) ending ...3D3 and it may well be a voltage stabiliser.

There are small numbers near the base 3F/506.
Thanks

B

[turretslug]

Is there any chance that it's an 8D3, Brimar's EF91 counterpart? Though the all-over gettering sounds different, that is something I've seen more often with references like the 85A2.

[Radio Wrangler]

Voltage stabiliser, B7G? I immediately thought 'OA2' and then my brane wurked for a moment. Why would a voltage stabiliser need a getter? They're gas filled.

So then I looked at the r-type museum, and they have a nice picture of an OA2, complete with a nice brown getter at its top, like any normal miniature valve.

My brain started hurting.

Maybe they pumped them down, ran the getter and only then introduced an inert, low pressure, gas? a means to keep it from pollution by outgassing products?

More questions than answers. Have I missed something?

David

[Bazz4CQJ]

I cannot see inside it at all, so could be a 8D3 but all the EF91's I've seen (especially Mullard) are clear and have fairly distinctive structure. I'll see if the filament pins conduct.

I think that most (all ?) of the stabilisers I've seen are "opaque" and I believed it had to do with light having a small effect on the stability?

B

[CambridgeWorks]

There are various reference tubes b7g, ef91 size in the 75V to 90V range. Eg. 5651, 75c1, 85a2, 90c1, though tend to be black internally.
Rob

[Richardgr]

I don't think a picture hurts. Sometimes the manufacturer can be determined from the pip on top and other details.

[Ed_Dinning]

If no heater pin continuity (sometimes a link pin as interlock, 0R) chose most likely A & K pins and apply 250v through 100K to see if it lights up; look at voltage for Vreg

Ed

[G.Castle]

Sounds like, an ignitron, I think they're called They are fully silvered and were used in industrial pulse/timing circuits, bit like a thyratron.

Edit:
Cold cathode trigger tube?

[Bazz4CQJ]

Here is a picture. I've tried taking them on light and dark backgrounds, but the reflections make it difficult to get a good result. When I try to look through it with a light behind it I cannot see anything that helps.

Pins 4 and 5 don't connect.

B

[turretslug]

A peek at a CV4014 here (industrial/professional Z77/EF91 equivalent) revealed a getter coating over almost the entire interior of the envelope, I also recall CV4015s (ind/pro W77/EF92) in a similar state, so it seems that it's not unheard of for "conventional" valves to have generous gettering.

It's a shame that the likes of the 85A2 get and possibly need that dark coating, they'd show a cheerful glow otherwise, not to mention being a guide to operation.

Off-topic, but I wonder if anything can guard against helium accretion in gas-filled regulators, either externally through the glass from atmospheric presence or internally from trace trigger decay? Maybe it's too slow a process to be a problem under normal circumstances.

Crossed with Baz- pins 3 and 4?

[HG MICKE]

That looks the same as the early version of the Brimar EF91, 6AM6, 8D3. I have a few old stock still in the original boxes and the valve envelope is silvered internally around the electrode structure, the getter silvering at the top is slightly darker. Other information on the valve is 3F1/1506 made in England 8D3, the same is printed on another five that I have. The later versions that I have are internally coated in a dark grey shielding.

Colin

[Bazz4CQJ]

Originally Posted by turretslug

Crossed with Baz- pins 3 and 4?

Ah, brain-fade here . And... pins 3 and 4 do indeed show 4 ohms. So, full marks to Turretslug for identifying the 8D3 .

Many years ago, someone gave me a junked ex Royal Navy VHF set. It was a serious piece of kit and I've never seen so much silver plating. It used B7G and B9A's throughout, all marked as CV's and mostly with 100% silver coats from the the getters, presumably, "special quality". Checking out the corresponding industrial designations, few of them where anything unusual.

I'm doing a bit of valve stock sorting. Found a TT23 (UHF twin tetrode) with some newspaper wrapped around it. The TV listings showed "Tina and Tucker" were on and a gallon of Castrol motor oil was 18/6.

B

[Aub]

Originally Posted by Bazz4CQJ

]The TV listings showed "Tina and Tucker" were on and a gallon of Castrol motor oil was 18/6.

Wasn't it Tinga and Tucker? Whoomerang Boomerang and all that

Aub

[Bazz4CQJ]

Yeah...and then there was Willy Wombat and auntie Jean Morton, and soon afterwards... Jess Yates
B