Unmarked valve #1. - UK Vintage Radio Repair and Restoration Discussion Forum

JacKam_ · 1st Jul 2017, 3:03 pm

Hi, Can anyone identify this valve, please?

Thank you,

Jacek

PS. I have more unmarked valves, next one in a week. Let me have some fun too...

Cobaltblue · 1st Jul 2017, 4:07 pm

Hard to see on my phone help to know what the base is but looks similar to an 807

1st Jul 2017, 4:15 pm

Looks like a grid top indirectly pentode.

Boater Sam · 1st Jul 2017, 5:59 pm

B7 base? Or is it american UX? What heater volts? Separate cathode i.e. indirectly heated?

I can't get the 3rd pix to load.

ms660 · 1st Jul 2017, 6:11 pm

Looks like two heaters in series, is the centre tap brought out to one of the valve pins?

There's also some writing on the pinch but I can't quite make out what it says yet.

Lawrence.

HamishBoxer · 1st Jul 2017, 6:26 pm

Not 807 I don't think as wrong base.

Leon Crampin · 1st Jul 2017, 9:52 pm

Mazda construction, probably an AC/6 Pen.

Leon.

Skywave · 1st Jul 2017, 10:35 pm

Is it on an International Octal base? If so, it could be a 12E1 or one of the similar variants.

Al.

Alf · 1st Jul 2017, 10:45 pm

I suspect it's a B7 base, they usually have a split which can be seen.

PJL · 1st Jul 2017, 11:31 pm

It looks like its written on the pinch! I think this is a Mazda trait although the very plain anode structure looks odd.

Restoration73 · 2nd Jul 2017, 4:48 am

This is the 12 volt heater version of the 807, the 1625.

Radio Wrangler · 2nd Jul 2017, 5:35 am

We can definitely eliminate the 807 and 1625.

The third picture shows a connection from the anode going downwards into the pinch. The 807 family have top cap anode connections only, and have ceramic insulation bushes for the anode supports rather than relying on the micas alone.

So the top cap must be something else, probably G1, which is rather peculiar in a large-ish power valve.

Those look like beam-forming plates within the anode, yet the anode construction doesn't optimise heat dissipation in the target area. This looks either a very early beam tetrode or else a 'power pentode.

AC6/Pen doesn't have a top cap, the 7 pin base is enough for an indirectly heated pentode. So if there is a centre tapped heater, then one electrode would be pushed onto a TC to free a pin for it.

David

Leon Crampin · 2nd Jul 2017, 7:54 am

The AC6/Pen has a top cap anode. Mazda valves were better built than those of many of their competitors and one feature was rigidity.

Frequently, a support pin is anchored in the pinch without a corresponding lead being connected to it. Thus the anode assembly is held in the pinch and the "heater centre tap" may not actually be connected.

The AC6/Pen still gets my vote.

Leon.

ms660 · 2nd Jul 2017, 8:37 am

Quote:

Originally Posted by ms660

Looks like two heaters in series, is the centre tap brought out to one of the valve pins?

There's also some writing on the pinch but I can't quite make out what it says yet.

Lawrence.

On the pinch, pen/40/??/?(?)

? anyone.

Lawrence.

llama · 2nd Jul 2017, 8:43 am

Does the OP actually want to know or is the fun aspect "the thing"? Both valid by the way!
It would be useful to have some measurements from pin-to-pin. What is the (cold) heater resistance? Is it connected to any other pin (the centre tap theory)? Any other pins linked to each other? What current does the heater take (& hence voltage across it) when "glowing nicely"?

Having identified the heater, which pin has the greatest measured capacitance to it? - should be the cathode. What other capacitance values between pins?

Forensics!
Graham

Radio Wrangler · 2nd Jul 2017, 8:59 am

Sorry, Leon, but that anode connection isn't mounting rods into the pinch, it looks like it would offer very little mechanical rigidity with thin wire, a couple of right angles and some iffy looking weld. The TC could still be anode, but someone put extra work into that downwards connection.

Oddly Radiomuseum shows all electrodes to base pins then says it has a top cap but gives no mention of its connection

r-type says the TC is anode, shows no anode connection on the base, of course, and two unused pins. A TC anode for TV line output is definitely a good idea.

It fits except for the flimsiness of the anode to pinch connection.

good puzzle!

David

JacKam_ · 2nd Jul 2017, 9:37 am

I am happy that you like that puzzle. On the pinch is "Pen WO/28/S".

I got this valve from G4JQT. (Once again, Thank you, Ian)
Adding more photos, taken with different light, but I am going to use a polarization filter next time.

Thank you
Jacek

ms660 · 2nd Jul 2017, 9:46 am

Quote:

Originally Posted by JacKam_

I am happy that you like that puzzle. On the pinch is "Pen WO/28/S".

Adding more photos, taken with different light, but I am going to use a polarization filter next time.
Thank you
Jacek

That looks like pen/40/20/s, there's a reference to that number here:

http://collection.sciencemuseum.org....endd4020-valve

Can't find a clear glass version of it though.

Cold heater resistance should confirm if it's a 40 volt heater.

Lawrence.

Leon Crampin · 2nd Jul 2017, 10:04 am

David, you're quite right. I had missed the non-supportive anode connection.

Lawrence, I think you've nailed it. I have just checked a PenDD4020 and there are many similarities. My sample has a graphited coating on the inside of the bulb, which may not have been applied to the earlier versions of this valve.

Viewed on a better monitor, I can see two horizontal connecting bars below the pentode which may connect the 2 diode sections to the pinch upright rods. A better picture of the top of the valve would then confirm the top cap connection as being g1.

Interestingly, my PenDD4020 sample also has the "heater centre tap" - not connected below the pinch. No doubt the high heater voltage versions had a long heater coil which Mazda wisely supported at its centre. There's no connection to it.

So, almost nailed. There was, however a PenDD4021 which was a higher current version. A test to distinguish this from a 4020 would have to be made electrically. There were also a couple of Mazda odballs - a 12V version for (monster?) car radios and a 6V version for Philco. As Lawence suggests, a heater test, preferably by running the valve up on a power supply should find these.

An interesting puzzle - we need confirmation that early versions of these valves were not graphited internally.

Leon.

If you look at the top cap, there's good evidence of the solder fatigue which these valves suffer from, which I detailed in another post. Reflowing the joint usually fixes them for another 70 years.

Leon Crampin · 2nd Jul 2017, 10:45 am

Consumed with curiosity, I've just opened my Murphy A30C which uses an AC/2PenDD.

On examining this valve, there's no heater centre support (it has a 4V heater) but the construction is otherwise very similar. This original pre-war green type valve is graphited internally. I re-flowed the joint to the cap.

Leon.

1st Jul 2017, 4:07 pm	#2
Cobaltblue Moderator Join Date: Dec 2010 Location: Exeter, Devon and Poole, Dorset UK. Posts: 6,875	Re: Unmarked valve #1. Hard to see on my phone help to know what the base is but looks similar to an 807 __________________ Invisible airwaves crackle with life or at least they used to Mike T BVWS member. www.cossor.co.uk

1st Jul 2017, 4:15 pm	#3
Guest Guest Posts: n/a	Re: Unmarked valve #1. Looks like a grid top indirectly pentode.

1st Jul 2017, 5:59 pm	#4
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: Unmarked valve #1. B7 base? Or is it american UX? What heater volts? Separate cathode i.e. indirectly heated? I can't get the 3rd pix to load. Last edited by Boater Sam; 1st Jul 2017 at 6:01 pm. Reason: added no pix

1st Jul 2017, 6:11 pm	#5
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Unmarked valve #1. Looks like two heaters in series, is the centre tap brought out to one of the valve pins? There's also some writing on the pinch but I can't quite make out what it says yet. Lawrence.

1st Jul 2017, 6:26 pm	#6
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Unmarked valve #1. Not 807 I don't think as wrong base. __________________ G8JET BVWS Archivist and Member V.M.A.R.S

1st Jul 2017, 3:03 pm	#1
JacKam_ Pentode Join Date: Jul 2015 Location: Newbury, Berkshire, UK. Posts: 243	Unmarked valve #1. Hi, Can anyone identify this valve, please? Thank you, Jacek PS. I have more unmarked valves, next one in a week. Let me have some fun too... Attached Thumbnails

1st Jul 2017, 9:52 pm	#7
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Unmarked valve #1. Mazda construction, probably an AC/6 Pen. Leon.

1st Jul 2017, 10:35 pm	#8
Skywave Rest in Peace Join Date: Jun 2006 Location: Chard, South Somerset, UK. Posts: 7,457	Re: Unmarked valve #1. Is it on an International Octal base? If so, it could be a 12E1 or one of the similar variants. Al.

1st Jul 2017, 10:45 pm	#9
Alf Hexode Join Date: May 2005 Location: Wigan, Greater Manchester, UK. Posts: 479	Re: Unmarked valve #1. I suspect it's a B7 base, they usually have a split which can be seen.

1st Jul 2017, 11:31 pm	#10
PJL Dekatron Join Date: Sep 2005 Location: Seaford, East Sussex, UK. Posts: 5,997	Re: Unmarked valve #1. It looks like its written on the pinch! I think this is a Mazda trait although the very plain anode structure looks odd. Last edited by PJL; 1st Jul 2017 at 11:39 pm.

2nd Jul 2017, 4:48 am	#11
Restoration73 Nonode Join Date: Jun 2013 Location: Surbiton, SW London, UK. Posts: 2,801	Re: Unmarked valve #1. This is the 12 volt heater version of the 807, the 1625.

2nd Jul 2017, 5:35 am	#12
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,901	Re: Unmarked valve #1. We can definitely eliminate the 807 and 1625. The third picture shows a connection from the anode going downwards into the pinch. The 807 family have top cap anode connections only, and have ceramic insulation bushes for the anode supports rather than relying on the micas alone. So the top cap must be something else, probably G1, which is rather peculiar in a large-ish power valve. Those look like beam-forming plates within the anode, yet the anode construction doesn't optimise heat dissipation in the target area. This looks either a very early beam tetrode or else a 'power pentode. AC6/Pen doesn't have a top cap, the 7 pin base is enough for an indirectly heated pentode. So if there is a centre tapped heater, then one electrode would be pushed onto a TC to free a pin for it. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

2nd Jul 2017, 7:54 am	#13
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Unmarked valve #1. The AC6/Pen has a top cap anode. Mazda valves were better built than those of many of their competitors and one feature was rigidity. Frequently, a support pin is anchored in the pinch without a corresponding lead being connected to it. Thus the anode assembly is held in the pinch and the "heater centre tap" may not actually be connected. The AC6/Pen still gets my vote. Leon.

2nd Jul 2017, 8:43 am	#15
llama Octode Join Date: Jun 2006 Location: St Osyth, Nr Clacton, Essex, UK. Posts: 1,482	Re: Unmarked valve #1. Does the OP actually want to know or is the fun aspect "the thing"? Both valid by the way! It would be useful to have some measurements from pin-to-pin. What is the (cold) heater resistance? Is it connected to any other pin (the centre tap theory)? Any other pins linked to each other? What current does the heater take (& hence voltage across it) when "glowing nicely"? Having identified the heater, which pin has the greatest measured capacitance to it? - should be the cathode. What other capacitance values between pins? Forensics! Graham __________________ Half my stuff is junk - trouble is, I don't know which half!

2nd Jul 2017, 8:59 am	#16
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,901	Re: Unmarked valve #1. Sorry, Leon, but that anode connection isn't mounting rods into the pinch, it looks like it would offer very little mechanical rigidity with thin wire, a couple of right angles and some iffy looking weld. The TC could still be anode, but someone put extra work into that downwards connection. Oddly Radiomuseum shows all electrodes to base pins then says it has a top cap but gives no mention of its connection r-type says the TC is anode, shows no anode connection on the base, of course, and two unused pins. A TC anode for TV line output is definitely a good idea. It fits except for the flimsiness of the anode to pinch connection. good puzzle! David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

2nd Jul 2017, 9:37 am	#17
JacKam_ Pentode Join Date: Jul 2015 Location: Newbury, Berkshire, UK. Posts: 243	Re: Unmarked valve #1. I am happy that you like that puzzle. On the pinch is "Pen WO/28/S". I got this valve from G4JQT. (Once again, Thank you, Ian) Adding more photos, taken with different light, but I am going to use a polarization filter next time. Thank you Jacek Attached Thumbnails Last edited by JacKam_; 2nd Jul 2017 at 9:43 am.

2nd Jul 2017, 10:04 am	#19
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Unmarked valve #1. David, you're quite right. I had missed the non-supportive anode connection. Lawrence, I think you've nailed it. I have just checked a PenDD4020 and there are many similarities. My sample has a graphited coating on the inside of the bulb, which may not have been applied to the earlier versions of this valve. Viewed on a better monitor, I can see two horizontal connecting bars below the pentode which may connect the 2 diode sections to the pinch upright rods. A better picture of the top of the valve would then confirm the top cap connection as being g1. Interestingly, my PenDD4020 sample also has the "heater centre tap" - not connected below the pinch. No doubt the high heater voltage versions had a long heater coil which Mazda wisely supported at its centre. There's no connection to it. So, almost nailed. There was, however a PenDD4021 which was a higher current version. A test to distinguish this from a 4020 would have to be made electrically. There were also a couple of Mazda odballs - a 12V version for (monster?) car radios and a 6V version for Philco. As Lawence suggests, a heater test, preferably by running the valve up on a power supply should find these. An interesting puzzle - we need confirmation that early versions of these valves were not graphited internally. Leon. If you look at the top cap, there's good evidence of the solder fatigue which these valves suffer from, which I detailed in another post. Reflowing the joint usually fixes them for another 70 years.

2nd Jul 2017, 10:45 am	#20
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Unmarked valve #1. Consumed with curiosity, I've just opened my Murphy A30C which uses an AC/2PenDD. On examining this valve, there's no heater centre support (it has a 4V heater) but the construction is otherwise very similar. This original pre-war green type valve is graphited internally. I re-flowed the joint to the cap. Leon.