What is this please? - UK Vintage Radio Repair and Restoration Discussion Forum

Boater Sam · 18th Jun 2018, 10:18 am

Found in a junk box at the auction.
Built on a McMurdo International Octal base.
Contains a transformer, 2 PCBs, and a Ferrox cube core with a slug tuner.
Seems to have 1 transistor and a few resistors.
Marked "1000 c/s" so assumed some sort of oscillator?

turretslug · 18th Jun 2018, 11:27 am

"Oscillator" was my first thought, too, but maybe an alternative is a sharp 1kHz active AF filter? Is enough discernible through the dragonfly-in-amber treatment to work out the circuit and base connection? I see that CV2389 was supposedly the first CV designation applied to a transistor, so implying around mid-fifties, perhaps similar to the OC71 etc.

Boater Sam · 18th Jun 2018, 1:00 pm

Trying to work the circuit out is very difficult, the components are on and between 2 paxolin boards, point to point wired, not PCBs.
There are 6 leads visible on the iron cored transformer, ( may be more onto the pins), 6 on the ferrite tuned transformer, 3 resistors,470,2K,56 ohms, 2 ceramic caps,and the transistor CV2389.

Radio Wrangler · 18th Jun 2018, 3:00 pm

Oscillator is a possibility, but I'm inclined to suspect it's a tone decoder.

David

M0FYA Andy · 18th Jun 2018, 4:06 pm

I have one of those! I've always thought it was a Post Office part. I'll dig it out and see if it has any identifying numbers.

Dave757 · 18th Jun 2018, 11:13 pm

Hi

Is this any help?

Kind regards
Dave

Biggles · 20th Jun 2018, 5:23 pm

I would say it could be a plug in tone decoder. The coil will be tuned to a particular frequency, probably audio, and either pass or reject depending on design. I used to work on Motorola equipment which employed plug-ins to decode in-band audio frequency sequences, although yours seem to be a good deal earlier than the ones I have seen.
Alan.

Radio Wrangler · 21st Jun 2018, 12:02 am

The earlier generation tone decoders were vibrating reed devices.

David

Biggles · 21st Jun 2018, 9:11 pm

I think the old radio control systems also used tuned reeds. It's a long time ago now...
Alan.

18th Jun 2018, 10:18 am	#1
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	What is this please? Found in a junk box at the auction. Built on a McMurdo International Octal base. Contains a transformer, 2 PCBs, and a Ferrox cube core with a slug tuner. Seems to have 1 transistor and a few resistors. Marked "1000 c/s" so assumed some sort of oscillator? Attached Thumbnails

18th Jun 2018, 11:27 am	#2
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,394	Re: What is this please? "Oscillator" was my first thought, too, but maybe an alternative is a sharp 1kHz active AF filter? Is enough discernible through the dragonfly-in-amber treatment to work out the circuit and base connection? I see that CV2389 was supposedly the first CV designation applied to a transistor, so implying around mid-fifties, perhaps similar to the OC71 etc.

18th Jun 2018, 1:00 pm	#3
Boater Sam Banned Join Date: Dec 2013 Location: Middlewich, Cheshire, UK. & Winter in the Philippines. Posts: 3,897	Re: What is this please? Trying to work the circuit out is very difficult, the components are on and between 2 paxolin boards, point to point wired, not PCBs. There are 6 leads visible on the iron cored transformer, ( may be more onto the pins), 6 on the ferrite tuned transformer, 3 resistors,470,2K,56 ohms, 2 ceramic caps,and the transistor CV2389.

18th Jun 2018, 3:00 pm	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: What is this please? Oscillator is a possibility, but I'm inclined to suspect it's a tone decoder. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

18th Jun 2018, 4:06 pm	#5
M0FYA Andy Nonode Join Date: May 2007 Location: Preston, Lancashire, UK. Posts: 2,511	Re: What is this please? I have one of those! I've always thought it was a Post Office part. I'll dig it out and see if it has any identifying numbers.

20th Jun 2018, 5:23 pm	#7
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: What is this please? I would say it could be a plug in tone decoder. The coil will be tuned to a particular frequency, probably audio, and either pass or reject depending on design. I used to work on Motorola equipment which employed plug-ins to decode in-band audio frequency sequences, although yours seem to be a good deal earlier than the ones I have seen. Alan.

21st Jun 2018, 12:02 am	#8
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,858	Re: What is this please? The earlier generation tone decoders were vibrating reed devices. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

21st Jun 2018, 9:11 pm	#9
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: What is this please? I think the old radio control systems also used tuned reeds. It's a long time ago now... Alan.