Mystery transformer - UK Vintage Radio Repair and Restoration Discussion Forum

kestrelmusic · 29th Dec 2018, 6:55 pm

I have found, in a job lot of odds and ends, a mystery transformer.

The label on top reads A (crown) M Ref No 10K/13259. Dimensions are 5cm side to side across the laminations, 3cm high.

Two pairs of terminals labelled IP OP and IS OS (obviously primary and secondary). DC resistance of the primary is 4.8 ohms and the secondary 1260 ohms.

However, I have no idea what this transformer may have been. Could it be an intervalve transformer? Or might it have been something more specialised? If anyone has some information I'd love to know!

Pics attached.

Ed_Dinning · 29th Dec 2018, 8:10 pm

Hi, it looks like the input/ coupling transformers as used in aircraft intercoms
The A1134 is a typical example, possibly about a 3:1 ratio. I believe there are 2 or 3 different versions

Ed

M0FYA Andy · 29th Dec 2018, 8:23 pm

As Ed says, it is the style used in intercom amplifiers.
I've checked the manual for the A1134, but this one doesn't feature in the parts list. AP1086 tells us it is a Transformer Type 870, with 200 turns of 34swg wire on the primary and 700 turns of 42swg wire on the secondary.

Andy

Radio Wrangler · 31st Dec 2018, 6:35 am

Old aircraft systems used carbon mikes, so a step up transformer from their low impedance could save an AF stage

David

29th Dec 2018, 6:55 pm	#1
kestrelmusic Hexode Join Date: Feb 2008 Location: Wrexham, North Wales, UK. Posts: 466	Mystery transformer I have found, in a job lot of odds and ends, a mystery transformer. The label on top reads A (crown) M Ref No 10K/13259. Dimensions are 5cm side to side across the laminations, 3cm high. Two pairs of terminals labelled IP OP and IS OS (obviously primary and secondary). DC resistance of the primary is 4.8 ohms and the secondary 1260 ohms. However, I have no idea what this transformer may have been. Could it be an intervalve transformer? Or might it have been something more specialised? If anyone has some information I'd love to know! Pics attached. Attached Thumbnails

29th Dec 2018, 8:10 pm	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Mystery transformer Hi, it looks like the input/ coupling transformers as used in aircraft intercoms The A1134 is a typical example, possibly about a 3:1 ratio. I believe there are 2 or 3 different versions Ed

29th Dec 2018, 8:23 pm	#3
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: Mystery transformer As Ed says, it is the style used in intercom amplifiers. I've checked the manual for the A1134, but this one doesn't feature in the parts list. AP1086 tells us it is a Transformer Type 870, with 200 turns of 34swg wire on the primary and 700 turns of 42swg wire on the secondary. Andy

31st Dec 2018, 6:35 am	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,871	Re: Mystery transformer Old aircraft systems used carbon mikes, so a step up transformer from their low impedance could save an AF stage David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done