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Old 16th Jun 2018, 2:25 pm   #21
David Simpson
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Default Re: Mystery valve

Graham, what valve tester do you have ?
Perhaps you could firstly just apply a heater voltage rising up to 6/6.3V to the suspected heater pins, without any HT or grid voltage. See if both filaments give a nice orangy/red glow. Then take a stab at cathode, and a low HT on one or the other suspected anodes, and see if one or two mA flow under Diode conditions. Then apply a hefty Grid voltage to a suspected grid pin & see what Ia does, when you slowly reduce Vg.
Its a bit of a trial & error exercise, but by careful adjustment of electrode voltages & a steady eye on Ia, you might be able to work out the electrode configuration. DDT, DP,TP or whatever. Its a lot of fannying about, but identification can be done.

Regards, David
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Old 16th Jun 2018, 3:22 pm   #22
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Default Re: Mystery valve

Surely if you can get a couple of ma to flow from anode to cathode the grids would act like potential dividers.
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Old 16th Jun 2018, 5:02 pm   #23
David Simpson
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Default Re: Mystery valve

Proven valve theory :- current flows from Cathode to Anode. Electrons being negatively charged, can have their flow controlled by negative Vg.
All I'm saying is - by safe trial & error - for Graham to try & determine the separate structures within the glass envelope. Be it a Triode Pentode or whatever.
If for example he has an AVO VCM(or can get access to one), he could easily determine "heater continuity" before any voltage is applied to Anodes, Screen, Grids, or whatever. The thumbwheel switch would soon reveal H+ & H-, for example. Careful examination under a magnifying glass, coupled with trying the remaining 7 thumbwheels, then gently applying the appropriate voltages to achieve Ia, should reveal the remaining electrode functions. e.g. D1,D2, A1, A2, G, & so on. Reverse referencing the AVO VDM, and cross referencing with an ILIFFE valve data book,(or try the Valve Museum Site) should reveal near enough the valve's identity.
I've done it occasionally, and yes - its a lot of time-consuming fannying about. If he's got 6 valves, say, and they're worth a tenner each, then its worthwhile.

Regards, David
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Old 16th Jun 2018, 5:22 pm   #24
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Default Re: Mystery valve

There are only two of these valves,they came from a radio amateur along with a box of transmitting valves.the heaters are definitely across pins 4-5 with pin 1 as an anchor point.whether this is connected to anything else Im not sure.also the C is on the triode anode not on the glass,there is a etch code on them which looks like B 3 J 1.This is a Blackburn code as you say unfortunately the code usually above this giving the type is missing.I have a Avo valve tester and will have a go at finding heater voltage/current later tonight.
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Old 16th Jun 2018, 5:29 pm   #25
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Default Re: Mystery valve

Be a little careful with the heater testing. We'd normally apply the voltage between pins 4 and 5 but it's possible, theoretically at least, that the two heaters are actually meant to run at different currents, with the supply voltage applied between pin 1 and each of pins 4 and 5. It would be a shame to ramp the voltage up across the two in series and blow one while trying to get the other one up to 'full' brightness.

Cheers,

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Old 16th Jun 2018, 5:53 pm   #26
David Simpson
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Default Re: Mystery valve

Aye GJ, if Graham tries the "H" (Heater Continuity) test first on his AVO VCM, then only a few uA will pass through the filament as the VCM is just acting as a Valve Voltmeter reading a slight resistance. Then he should try gently raising the Heater Volts fine control switch up to 6.3V applied to the revealed H+ & H-. In fact, if he uses the "TOP CAP" Panel & a couple of crock-clip leads & an MM on the 1A AC range, he can monitor Ih. I always use a good old AVO8 MM for such current tests. If anything is wrong then it will quickly trip. One would normally expect Ih to be in the low hundreds of mA for a bog standard B9A valve.

Regards, David
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Old 16th Jun 2018, 8:06 pm   #27
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Default Re: Mystery valve

Were there any U series triode-pentodes? If so, 100mA heater current is a possibility. Otherwise 300mA is the likely minimum.

It is likely that the hot heater resistance will be around 4-6 times the cold resistance so that should be a guide.
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Old 16th Jun 2018, 8:18 pm   #28
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Default Re: Mystery valve

Crazy theory but two anodes strapped together, triode and pentode heaters in series with a pinout connection at their junction.....switchable valves in one envelope?

So far as I can make out pin 8 is anode(s)

I also looked in Iliffe valve data book and national valve museum, nothing I could see.

Complete pinout might help.

Lawrence.
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Old 16th Jun 2018, 9:34 pm   #29
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Default Re: Mystery valve

There was definitely a UCL82, 100mA heater series connection. Looked about the shape of the valve in question.
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Old 16th Jun 2018, 9:42 pm   #30
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Default Re: Mystery valve

Pcl86?
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Old 16th Jun 2018, 10:32 pm   #31
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Default Re: Mystery valve

An ?CL8? is a 'busy' valve. With only nine pins every one really has to earn its keep. Assigning one to a heater tap, of all things, must mean that the contents of the envelope are very peculiar indeed. It isn't going to be any of the standard valves.

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Old 16th Jun 2018, 11:10 pm   #32
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Default Re: Mystery valve

It looks a bit like a PCL88.

Another crazy idea is that the larger valve structure is a Tetrode.
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Old 17th Jun 2018, 5:43 am   #33
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Default Re: Mystery valve

With 9 pins, and 3 used for the heater (tapped) then there are 6 left. If it is a triode-pentode, the only sane way I can see to get the electrodes onto 6 pins is to have a common cathode and have the suppressor grid of the pentode connected to that internally. Then the 6 pins would be cathodes/g3; triode grid; triode anode; pentode control grid; pentode screen grid; pentode anode.

Other odd thoughts...

Wasn't there an American double triode where the cathode of one section was internally connected to the grid of the other? Can't think that applies here, but...

What if the 2 sections were both pentodes and internally wired in parallel? So externally the valve is a pentode, the odd construction is just to get enough anode area into a sensible-height envelope.
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Old 17th Jun 2018, 10:14 am   #34
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Default Re: Mystery valve

I've not seen a valve like that which wasn't a PCL85 or 86.

Peter
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Old 17th Jun 2018, 11:12 am   #35
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Default Re: Mystery valve

The 6CD6 is a double pentode with a common anode with all the other electrodes internally connected in parallel.
In the US there was one made with a tall anode and only one set of electrodes for some strange reason.
https://www.google.co.uk/search?q=6c...69zMcRcZlTDlM:
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Old 17th Jun 2018, 11:47 am   #36
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Default Re: Mystery valve

Quote:
Originally Posted by Peter.N. View Post
I've not seen a valve like that which wasn't a PCL85 or 86.
Until now (neither the '85 nor the '86 has a heater tap on pin 1, but this valve does).

Quote:
Originally Posted by TonyDuell View Post
... What if the 2 sections were both pentodes and internally wired in parallel? So externally the valve is a pentode, the odd construction is just to get enough anode area into a sensible-height envelope.
If we look at the OP's fourth picture, in post #12, we can see the mica below the small section. There is the cathode tube in the middle and the two copper-coloured control grid support rods either side of it. That's all. So it is just a triode.

Cheers,

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Old 17th Jun 2018, 2:19 pm   #37
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Default Re: Mystery valve

There also seems to be a small structure built above the top mica, reminiscent of the triode in an ECL80 or maybe a diode as in an American valve I once saw (sorry can't remember the type).
So maybe it could be a special, in which case very good luck in getting any info, or one of the latter types of multiple valve that were produced in the dying days like the ECLL80, ECLL800, and other continental (German) types that were made by Mullard for Valvo, Siemens, Telefunken . . .
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Old 17th Jun 2018, 2:27 pm   #38
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Default Re: Mystery valve

The anode structure of the large valve looks similar to the PCL805/85 on the r-type.org website.

I have one of these but I can't find it at the moment.
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Old 17th Jun 2018, 8:26 pm   #39
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Default Re: Mystery valve

The structure above the top mica is probably a heatsink for one of the pentode grids.

The problem we have is that many triode-power pentodes look fairly similar. An exception is the xCL82, which has a triode of the same height as the pentode. So we know that this is not an '82.

I suspect this is a special. They took an existing TP design and modified the heater arrangements, perhaps to avoid cathode interface developing if one of the cathodes was unused (but hot) for a long time.
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Old 17th Jun 2018, 8:35 pm   #40
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Default Re: Mystery valve

I've checked from 0 to Z on this site:

https://frank.pocnet.net/sheetsD.html

Couldn't find anything that fits the bill when searching for tP in the system column.

Would like to know for sure if the two anodes are strapped together, they look like it in the photo.

Lawrence.
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