Air Ministry Valve Tester - UK Vintage Radio Repair and Restoration Discussion Forum

M0FYA Andy · 6th Sep 2018, 6:19 pm

All the recent threads on valve testers reminds me of a question I've been meaning to ask.
Was the Air Ministry Valve Tester Type 4, a rather fuzzy drawing of the front panel extracted from the AP attached, a commercially available unit, or specially designed and made for the Air Ministry?

It does look reminiscent of the early Avo types, but I don't have one to compare. I do have three examples of the AM unit, best described as 'careworn'.

Andy

David Simpson · 6th Sep 2018, 8:21 pm

Andy, don't know about other folk, but I cannot open a doxc document. Any chance of a pdf or similar, please ?
The "Type 4" must have been obsolete by the time I became involved with RAF valve testers in the 60's. Just the CT160 was in use.
That link I mentioned a few days ago about Denis Tabor's article in the Winter 1981 copy of the BVWS Bulletin, mentions I think the type IV and others which he worked on during his RAF career from 1945 to 1952. There is also a picture I think.

Regards, David

Jeremy M0RVB · 6th Sep 2018, 8:34 pm

I have the 4A - the bottom one here: https://www.tubecollector.org/equipm...lvetesters.htm

Not sure what docs I have, buried in the workshop somewhere.

Given the sockets it 'feels' like it's bespoke for military stuff around at that time.

M0FYA Andy · 6th Sep 2018, 9:27 pm

I've printed the .docx to a PDF, attached.

I extracted this picture from a copy of the AP downloaded from the WS19 Group, so I'd better not upload the whole document, however I think I have a paper manual (I need to dig it out to check if it's the same document) which I can scan if anybody is interested.

Originally the tester included the L4 base, but on a couple of the testers I have this has been removed and replaced with a B7G base, so they have been updated at some time.

My plan, if I ever find time, is to build at least one good example out of the three, the wooden cases need major refurbishment and there is a lot of perished wiring.

Andy

GMB · 6th Sep 2018, 11:51 pm

I have a nice Type 4 that only needed minor restoration, and seems to work OK.

I do wonder why the air ministry felt it was necessary to have their own tester when they could have just bought one of the commercial models, or even had one adapted to their requirement (if it was so different).

It tests using AC so like a number of its contemporary commercial testers. I think the magic eye for insulation test is a bit unusual.

The Type 4 and Type4A mainly seem to differ in a significantly different circuit of the magic eye.

joebog1 · 7th Sep 2018, 4:08 am

to: David Simpson, Libre Office will read and write docx documents and is available for almost any platform.

MOFYA, I am always interested in valve testers, maybe a copy of the manual would be nice?

Joe

M0FYA Andy · 7th Sep 2018, 9:28 am

I'd better check whether my testers are actually Type 4 or Type 4A, the trouble is they are at the bottom of a 'wall' of items carefully stacked to minimise the space they take up!
I've dug out my paper manual, it turns out to be a rather poor photocopy of the same document available for download from the 19 Set Archive, AP2537A, but I'll try to scan it.

Andy

GMB · 7th Sep 2018, 9:34 am

I have copies of both the type 4 and type4a manuals but I need to check their source before publishing them. I have been meaning to do this but didn't think there was much interest.

M0FYA Andy · 7th Sep 2018, 10:31 am

George, I would certainly be very interested and grateful!

Andy

M0FYA Andy · 7th Sep 2018, 11:05 am

This is the circuit scanned from my poor quality photocopy.

Andy

joebog1 · 7th Sep 2018, 11:29 am

Thanks Andy!!

It is, as you said fairly poor, BUT it's a new thing to look at and analyze!!
I am still trying to "invent my own" after my old AVO MKII has become sicker and sicker.
It's mostly the static and the meter, but as I live in 20% humidity, and plus 35 degrees C temperatures, it's hard to prevent.

Thanks, Joe.

ms660 · 7th Sep 2018, 3:22 pm

Re: The Type 4 tester schematic, what, if any, are the circuit functional differences between the gm 100mA and gm 10mA switch positions, the switch contacts (1&2) for each section appear to be connected together for both the above switch positions?

Lawrence.

Jeremy M0RVB · 7th Sep 2018, 5:49 pm

Here's the circuit scan from the original manual, can't get it very flat because of the staples.

GMB · 7th Sep 2018, 11:22 pm

I have put both circuits on my web site so you can compare them.

http://air-ministry.uk/AMvalveTesterCircuits4and4A.pdf

Quote:

Re: The Type 4 tester schematic, what, if any, are the circuit functional differences between the gm 100mA and gm 10mA switch positions, the switch contacts (1&2) for each section appear to be connected together for both the above switch positions?

There are several wafers of that switch where the difference occurs. It just changes the sensitivity of the meter.

M0FYA Andy · 8th Sep 2018, 10:12 am

Very many thanks!

Andy

ms660 · 8th Sep 2018, 10:53 am

Quote:

Originally Posted by GMB

I have put both circuits on my web site so you can compare them.

http://air-ministry.uk/AMvalveTesterCircuits4and4A.pdf

Quote:

Re: The Type 4 tester schematic, what, if any, are the circuit functional differences between the gm 100mA and gm 10mA switch positions, the switch contacts (1&2) for each section appear to be connected together for both the above switch positions?

There are several wafers of that switch where the difference occurs. It just changes the sensitivity of the meter.

But it's not shown on the schematics unless I'm reading them wrong.

Lawrence.

GMB · 8th Sep 2018, 8:35 pm

Oh I see what you mean. There is clearly a drafting error, on both versions!

When I am back from holiday I will have a look to see what the actuality is.

6th Sep 2018, 8:21 pm	#2
David Simpson Nonode Join Date: Mar 2008 Location: Aberdeen, UK. Posts: 2,858	Re: Air Ministry Valve Tester Andy, don't know about other folk, but I cannot open a doxc document. Any chance of a pdf or similar, please ? The "Type 4" must have been obsolete by the time I became involved with RAF valve testers in the 60's. Just the CT160 was in use. That link I mentioned a few days ago about Denis Tabor's article in the Winter 1981 copy of the BVWS Bulletin, mentions I think the type IV and others which he worked on during his RAF career from 1945 to 1952. There is also a picture I think. Regards, David

6th Sep 2018, 8:34 pm	#3
Jeremy M0RVB Hexode Join Date: Jul 2003 Location: Leeds, West Yorkshire, UK. Posts: 458	Re: Air Ministry Valve Tester I have the 4A - the bottom one here: https://www.tubecollector.org/equipm...lvetesters.htm Not sure what docs I have, buried in the workshop somewhere. Given the sockets it 'feels' like it's bespoke for military stuff around at that time.

6th Sep 2018, 11:51 pm	#5
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,100	Re: Air Ministry Valve Tester I have a nice Type 4 that only needed minor restoration, and seems to work OK. I do wonder why the air ministry felt it was necessary to have their own tester when they could have just bought one of the commercial models, or even had one adapted to their requirement (if it was so different). It tests using AC so like a number of its contemporary commercial testers. I think the magic eye for insulation test is a bit unusual. The Type 4 and Type4A mainly seem to differ in a significantly different circuit of the magic eye.

7th Sep 2018, 4:08 am	#6
joebog1 Banned Join Date: Jun 2015 Location: Mareeba, North Queensland, Australia Posts: 2,704	Re: Air Ministry Valve Tester to: David Simpson, Libre Office will read and write docx documents and is available for almost any platform. MOFYA, I am always interested in valve testers, maybe a copy of the manual would be nice? Joe

7th Sep 2018, 9:28 am	#7
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: Air Ministry Valve Tester I'd better check whether my testers are actually Type 4 or Type 4A, the trouble is they are at the bottom of a 'wall' of items carefully stacked to minimise the space they take up! I've dug out my paper manual, it turns out to be a rather poor photocopy of the same document available for download from the 19 Set Archive, AP2537A, but I'll try to scan it. Andy

7th Sep 2018, 9:34 am	#8
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,100	Re: Air Ministry Valve Tester I have copies of both the type 4 and type4a manuals but I need to check their source before publishing them. I have been meaning to do this but didn't think there was much interest.

7th Sep 2018, 10:31 am	#9
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: Air Ministry Valve Tester George, I would certainly be very interested and grateful! Andy

7th Sep 2018, 11:29 am	#11
joebog1 Banned Join Date: Jun 2015 Location: Mareeba, North Queensland, Australia Posts: 2,704	Re: Air Ministry Valve Tester Thanks Andy!! It is, as you said fairly poor, BUT it's a new thing to look at and analyze!! I am still trying to "invent my own" after my old AVO MKII has become sicker and sicker. It's mostly the static and the meter, but as I live in 20% humidity, and plus 35 degrees C temperatures, it's hard to prevent. Thanks, Joe.

7th Sep 2018, 3:22 pm	#12
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Air Ministry Valve Tester Re: The Type 4 tester schematic, what, if any, are the circuit functional differences between the gm 100mA and gm 10mA switch positions, the switch contacts (1&2) for each section appear to be connected together for both the above switch positions? Lawrence. Last edited by ms660; 7th Sep 2018 at 3:28 pm. Reason: clarification

8th Sep 2018, 10:12 am	#15
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: Air Ministry Valve Tester Very many thanks! Andy

8th Sep 2018, 8:35 pm	#17
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,100	Re: Air Ministry Valve Tester Oh I see what you mean. There is clearly a drafting error, on both versions! When I am back from holiday I will have a look to see what the actuality is.