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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 17th Jun 2018, 8:55 pm   #41
barretter
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Default Re: Mystery valve

Quote:
Originally Posted by RF Burn View Post
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 . . .
You can find the data sheets for the valves you mention on www.tubedata.org
(I don't think Mullard made them for the German companies, by the way) but neither of them resemble the mystery valve. I do, however, have several ECL85s which are virtually identical to it.
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Old 17th Jun 2018, 8:57 pm   #42
radiograham
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Default Re: Mystery valve

This is what I have managed to find out with my valve tester, strange I know but this is how it seems to be. The pinout tallys with a PCL85, 18 volts heater voltage across pins 4 and 5 and the pentode tests as such the difference then is that pin 1 is definitely the junction of the two heaters. 1 and 4 is the triode heater which takes 6.3 volt at 300ma, 1 and 5 is the pentode heater taking 12.6 volt at 300 mA, the two anodes are connected together internally. When you just feed the 6.3 volt heater you can test the triode, when you feed the 12.6volt on its own you can test the pentode.
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Old 17th Jun 2018, 9:14 pm   #43
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Default Re: Mystery valve

So it appears to be a special, built from a PCL85.
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Old 17th Jun 2018, 9:19 pm   #44
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Default Re: Mystery valve

How curious. Could it have been a niche-purpose modulating, gating or level-shifting valve based on PCL85 structure and jigs to minimise initial investment? Perhaps for a mobile (whether land, air or sea) application where 12.6V nominal heater stringing was needed. There were a few weird and wonderful valves cooked up for machine control interface and computer applications, too. We need that time machine!
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Old 17th Jun 2018, 10:39 pm   #45
radiograham
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Default Re: Mystery valve

The only clue about these that I have is that the person I bought them from was selling them for his son who was a radio amateur, Am I right in thinking that they must have been used individually by switching in the individual heaters? With the anodes connected together if both heaters were in operation would the two valves be in parallel?
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Old 17th Jun 2018, 10:53 pm   #46
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Default Re: Mystery valve

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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?
This is what I thought,operation of triode or pentode by switching the relevant heaters.
Graham.
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Old 18th Jun 2018, 2:51 am   #47
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Default Re: Mystery valve

Would it be for a two power radio transmitter?
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Old 18th Jun 2018, 11:29 am   #48
G8HQP Dave
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Default Re: Mystery valve

Might be more useful in a guitar amp, but this would not have been the original purpose.
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Old 18th Jun 2018, 12:34 pm   #49
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Default Re: Mystery valve

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Originally Posted by turretslug View Post
How curious. Could it have been a niche-purpose modulating, gating or level-shifting valve based on PCL85 structure and jigs to minimise initial investment? Perhaps for a mobile (whether land, air or sea) application where 12.6V nominal heater stringing was needed. There were a few weird and wonderful valves cooked up for machine control interface and computer applications, too. We need that time machine!
I think that this idea is probably closest to the truth, as a lot of developments seem to have been made in the latter valve days for mobile/battery powered valves that could be used on 6/12/24/48 Volt battery supplies and/or be very rugged, these being apparently modifications to standard types in order to save tooling costs especially where the production run was not very high.

A centre tapped heater of 6.3/12.6 Volts suggests to me an ECC81/2/3 heater setup were you wire in series (across the ends) for 12 Volt and parallel (between CT and ends) for 6 Volt supply. I believe that 6 volt batteries were still being used on vehicles at that time (and still are?).

I will not hazard a guess as to the actual intended use for this oddball, suffice to say that as the world of electronics applications was expanding rapidly during that time, it could be almost anything. Only one real clue here, it must have been something worthwhile (or high budget military?) to interest a company like Mullard/Philips . . .

I would forget the amateur radio connection, that is probably just a red herring.
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Old 18th Jun 2018, 2:17 pm   #50
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Default Re: Mystery valve

Triode part as a mute function leaving the pentode as the amplifier?
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Old 19th Jun 2018, 11:53 pm   #51
radiograham
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Default Re: Mystery valve

Just one further comment on this ,Does anyone know when Mullard stopped making valves what happened to all the records of the company,For instance when Blackburn closed was everything dumped or was there any attempt saving anything for historical purposes/posterity.
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Old 20th Jun 2018, 2:26 pm   #52
Craig Sawyers
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Default Re: Mystery valve

It all is here http://brimaruk.com/menugbvp/great-b...valve-project/ being restored in order to remanufacture valves again.

A lot was scattered overseas - they tracked it down and raised enough money to get it all shipped back.

Craig
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Old 20th Jun 2018, 4:47 pm   #53
radiograham
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Default Re: Mystery valve

I have seen this venture and hope it comes to fruition, I was wondering about the what must have been the vast amount of documentation in their records, whether any of this was saved from disposal, something like was done with Marconi etc. Graham.
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Old 20th Jun 2018, 8:14 pm   #54
barretter
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Default Re: Mystery valve

Mullard was completely taken over by Philips in 1928(!) so any documents might be in the Philips Company Archive in Eindhoven. Their email address is:
pca@philips.com
but the problem is you have no designation for the valve. I suggest you scrutinise the valve's bulb with a magnifying glass, possibly with a light behind it which might show up the permanent ink marking of the code (if there is one).
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