Signal generator info please. - UK Vintage Radio Repair and Restoration Discussion Forum

derek.ireland · 27th Jan 2018, 12:53 pm

Before I make a start on it, can anybody give me some info on this sig gen please? Model no. pic to get the lettering on front panel .

Took two hours to slowly bring up to voltage. Lovely sine and square wave. One EF50 not used but heater wired, don't see the point.

Thank for any help.

Hartley118 · 27th Jan 2018, 1:25 pm

Quite presentable, but not a commercial product. Looks like it could be a bespoke audio oscillator designed and built by a company's test technicians.

Valves are low cost ex-WD. Maybe 1940s/early 50s? Is there a date on one of those electrolytics?

Martin

Radio Wrangler · 27th Jan 2018, 2:48 pm

It looks like a re-purposed war surplus chassis.

That dual pot is far too serious a component for most period home-brewers to buy. So I'm with Martin on some company's technicians building it.

It seems a bit too early for 8 Ohm speakers, and maybe not enough power for speaker testing.

As an R-C oscillator, the game is to find how they stabilised the amplitude.

David

turretslug · 27th Jan 2018, 3:27 pm

A mischievous and likely spurious thought occurs to me: is that EF50 heater being used to stabilise the feedback, did they pre-empt Mr. Hewlett and Mr. Packard?

I expect the time-constant would be too large, though.

turretslug · 27th Jan 2018, 4:14 pm

Well, actually looking at the under-chassis shows that the under-employed EF50 simply has heaters paralleled with the others. That varnished choke looks very Marconi. I'm sure I'd seen a few cases where EF50s were so numerous on the surplus market that they were even used as shunt ripple-cancellers for low-power circuits, or maybe it had been a buffer stage.

Radio Wrangler · 27th Jan 2018, 4:34 pm

Philips did a heck of a job hiding the EF50 and its production processes from the Nazis. I think the were very valuable beasties before the end of the war. Bill's bulb was late-middle thirties. I hadn't worried about whether he might have been pre-empted, but I did wonder about the heater as a thermistor, but the mass of the cathode would slow it too much. an ordinary bulb is better.

David

27th Jan 2018, 12:53 pm	#1
derek.ireland Tetrode Join Date: Sep 2007 Location: Norwich, Norfolk, UK. Posts: 50	Signal generator info please. Before I make a start on it, can anybody give me some info on this sig gen please? Model no. pic to get the lettering on front panel . Took two hours to slowly bring up to voltage. Lovely sine and square wave. One EF50 not used but heater wired, don't see the point. Thank for any help. Attached Thumbnails Last edited by Station X; 27th Jan 2018 at 12:58 pm. Reason: Readability.

27th Jan 2018, 1:25 pm	#2
Hartley118 Nonode Join Date: Aug 2015 Location: Cambridge, Cambs. UK. Posts: 2,198	Re: Signal generator info please. Quite presentable, but not a commercial product. Looks like it could be a bespoke audio oscillator designed and built by a company's test technicians. Valves are low cost ex-WD. Maybe 1940s/early 50s? Is there a date on one of those electrolytics? Martin __________________ BVWS Member

27th Jan 2018, 2:48 pm	#3
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,876	Re: Signal generator info please. It looks like a re-purposed war surplus chassis. That dual pot is far too serious a component for most period home-brewers to buy. So I'm with Martin on some company's technicians building it. It seems a bit too early for 8 Ohm speakers, and maybe not enough power for speaker testing. As an R-C oscillator, the game is to find how they stabilised the amplitude. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

27th Jan 2018, 3:27 pm	#4
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,395	Re: Signal generator info please. A mischievous and likely spurious thought occurs to me: is that EF50 heater being used to stabilise the feedback, did they pre-empt Mr. Hewlett and Mr. Packard? I expect the time-constant would be too large, though.

27th Jan 2018, 4:14 pm	#5
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,395	Re: Signal generator info please. Well, actually looking at the under-chassis shows that the under-employed EF50 simply has heaters paralleled with the others. That varnished choke looks very Marconi. I'm sure I'd seen a few cases where EF50s were so numerous on the surplus market that they were even used as shunt ripple-cancellers for low-power circuits, or maybe it had been a buffer stage.

27th Jan 2018, 4:34 pm	#6
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,876	Re: Signal generator info please. Philips did a heck of a job hiding the EF50 and its production processes from the Nazis. I think the were very valuable beasties before the end of the war. Bill's bulb was late-middle thirties. I hadn't worried about whether he might have been pre-empted, but I did wonder about the heater as a thermistor, but the mass of the cathode would slow it too much. an ordinary bulb is better. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done