What was this for? Indicator Type74 - UK Vintage Radio Repair and Restoration Discussion Forum

Bill · 28th Jan 2019, 2:48 pm

No pictures, this item was dismantled 50 years ago....
About 1965 I bought an "Indicator type 74" from New Cross Radio in Manchester.
It cost 25shillings. The unit was a very well made grey plated steel chassis and case. The oil filled "mains" transformer input was 180volt 400c/s. A VCR139A/ECR30 (N.B.electrostatic deflection)tube and a few valves including an 807 which appeared to drive a rather crude scanning coil around the tube. This coil was on a c-shaped laminated iron former about half way along the tube but was not close fitting.
I have puzzled ever since as to what this unit was made for . It seemed far too heavy to be fitted in an aircraft , the most likely source of 400c/s power. Has anyone any ideas or even seen one,New Cross had a pile of them,maybe you also bought one?
Bill

M0FYA Andy · 28th Jan 2019, 3:30 pm

This would appear to have been used with various ground-based radar sets including the 'Light Warning Radar'. I don't have the relevant Air Publications, they may be available at TNA Kew, I can find some references if you want to dig deeper.

Andy

Bill · 1st Feb 2019, 11:44 am

Thanks Andy. It was the unusual E/M deflection coil with an E/S deflection tube that I found a bit odd. Are there other more common instances of this? Vaguely related to this, I have an NOS CV262/9MD6 radar tube which is magnetic deflection. If this was for a PPI display, I think the scanning coils would be motor driven, rotating round the tube neck?
Bill

G6Tanuki · 1st Feb 2019, 12:22 pm

Quote:

Originally Posted by Bill

If this was for a PPI display, I think the scanning coils would be motor driven, rotating round the tube neck?
Bill

Some early PPI displays did use a motor-driven coil assembly on the CRT; later ones used static coils and electromagnetic sine/cosine synchros - a kind of three-phase transformer with variable coupling - that took their information from similar devices attached to the PPI scanner.

M0FYA Andy · 1st Feb 2019, 12:55 pm

Wartime airborne radars such as H2S Mks I to III used an electrostatically scanned CRT (typically a VCR517) with the PPI signals derived from a sine-cosine resolver (Magslip) mounted on the scanner assembly, rotating with the aerial 'mirror'.
Magnetically scanned tubes came in post-war with H2S MkIV fitted to the Avro Lincoln.

A 'slow-burn' project of mine is to assemble a complete H2S MkIIB system.

Andy

M0FYA Andy · 1st Feb 2019, 12:59 pm

Just to be clear, a sine-cosine resolver is not a three-phase device. It has a two-phase output with the two phases 90 degrees apart.

Andy

dave walsh · 1st Feb 2019, 1:38 pm

I had a quick look on the VMARS site without finding anything from the Index Search but they seem to have items not necessarily listed. As a specialist Military Group it's worth asking. They were very helpful to me last year and a member even took the trouble to visit the archive in person and dig some info out for me!

Dave W

28th Jan 2019, 2:48 pm	#1
Bill Pentode Join Date: Dec 2005 Location: Denton, Manchester, UK. Posts: 187	What was this for? Indicator Type74 No pictures, this item was dismantled 50 years ago.... About 1965 I bought an "Indicator type 74" from New Cross Radio in Manchester. It cost 25shillings. The unit was a very well made grey plated steel chassis and case. The oil filled "mains" transformer input was 180volt 400c/s. A VCR139A/ECR30 (N.B.electrostatic deflection)tube and a few valves including an 807 which appeared to drive a rather crude scanning coil around the tube. This coil was on a c-shaped laminated iron former about half way along the tube but was not close fitting. I have puzzled ever since as to what this unit was made for . It seemed far too heavy to be fitted in an aircraft , the most likely source of 400c/s power. Has anyone any ideas or even seen one,New Cross had a pile of them,maybe you also bought one? Bill

28th Jan 2019, 3:30 pm	#2
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: What was this for? Indicator Type74 This would appear to have been used with various ground-based radar sets including the 'Light Warning Radar'. I don't have the relevant Air Publications, they may be available at TNA Kew, I can find some references if you want to dig deeper. Andy

1st Feb 2019, 11:44 am	#3
Bill Pentode Join Date: Dec 2005 Location: Denton, Manchester, UK. Posts: 187	Re: What was this for? Indicator Type74 Thanks Andy. It was the unusual E/M deflection coil with an E/S deflection tube that I found a bit odd. Are there other more common instances of this? Vaguely related to this, I have an NOS CV262/9MD6 radar tube which is magnetic deflection. If this was for a PPI display, I think the scanning coils would be motor driven, rotating round the tube neck? Bill

1st Feb 2019, 12:55 pm	#5
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: What was this for? Indicator Type74 Wartime airborne radars such as H2S Mks I to III used an electrostatically scanned CRT (typically a VCR517) with the PPI signals derived from a sine-cosine resolver (Magslip) mounted on the scanner assembly, rotating with the aerial 'mirror'. Magnetically scanned tubes came in post-war with H2S MkIV fitted to the Avro Lincoln. A 'slow-burn' project of mine is to assemble a complete H2S MkIIB system. Andy

1st Feb 2019, 12:59 pm	#6
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: What was this for? Indicator Type74 Just to be clear, a sine-cosine resolver is not a three-phase device. It has a two-phase output with the two phases 90 degrees apart. Andy

1st Feb 2019, 1:38 pm	#7
dave walsh Dekatron Join Date: Jan 2006 Location: Ramsbottom (Nr Bury) Lancs or Bexhill (Nr Hastings) Sussex. Posts: 5,817	Re: What was this for? Indicator Type74 I had a quick look on the VMARS site without finding anything from the Index Search but they seem to have items not necessarily listed. As a specialist Military Group it's worth asking. They were very helpful to me last year and a member even took the trouble to visit the archive in person and dig some info out for me! Dave W