Testgear Acton signal generator - UK Vintage Radio Repair and Restoration Discussion Forum

martin.m · 2nd Sep 2018, 12:45 am

I have just acquired a "Testgear Acton" signal generator. Am I correct in thinking that the miniature valves are ex military types? There are two of them, along with an EM81 "magic eye". I have tested the generator (not very scientifically) by connecting a short length of wire to the output socket and placing a transistor radio nearby to pick up the RF signal. All seems to be working from the LW band right up to VHF. Just out of curiosity, how could a vintage signal generator like this be set to an exact frequency?

Herald1360 · 2nd Sep 2018, 1:06 am

The valves are "Acorn" types- military surplus for sure!

Exact frequency setting- with difficulty back in the day! Maybe use a crystal referenced wavemeter like BC221 (also surplus!). Or compare with nearby frequency known station then extrapolate using the scale.

Calibration would probably be good enough for simple radio alignment activities though.

Sinewave · 2nd Sep 2018, 1:11 am

I set mine with a frequency counter.

Radio Wrangler · 2nd Sep 2018, 6:45 am

Most probably the valves are 954 with the top connector and 955 the one without.

This was a small manufacturer making things out of the mountains of surplus parts on the market in the 50's and into the 60's.

The accuracy was whatever it was and most users lived with it for fixing radios. You'll find things like this with user-added marks on the scales where it's been checked against known stations as a guide to making corrections.

The frequency meter of the period was the surplus BC221 which is a precision VFO with circuits to allow beats between it and a crystal oscillator to be heard in headphones so it can be trimmed. Each one had an enormous book of its individual dial reading to frequency table - which was printed in an automated test setup at the factory.

The output amplitude of sig gens like this one won't go low enough or be at all known enough to check receiver sensitivity, it's really a machine for getting dead receivers going and with care is good enough to align LW/MW domestic sets. The acorn valves mean it's better than many at the top end of its frequency range.

David

turretslug · 2nd Sep 2018, 8:31 am

The perspective makes it difficult to be certain, but that tuning capacitor with its one wide- and two close-spaced sections may be a surplus spare for the R1155 receiver. The characteristically waisted Sprague paper capacitors are likely US surplus (as paper capacitors, they're not above reproach but they are held to be better than many of that ilk) and the generator as a whole is an excellent snapshot of the mountain of surplus components in the wake of WW2. Those ceramic acorn valveholders are kind of rare nowadays- though no doubt some functionary consigned umpteen zillion to landfill at some point....

Fingers crossed that the EM81 still has some go in it.

As mentioned, should be a useful first-line checking device, if not lab-standard for frequency and level,

Colin

Ed_Dinning · 2nd Sep 2018, 7:00 pm

Hi Martin, I probably have spare vales/ magic eye if you need them.

Ed

martin.m · 2nd Sep 2018, 10:50 pm

Thanks to all who have replied. I love old technology and will enjoy using this generator.

Ed, thanks for your kind offer of spare valves. The EM81 seems bright enough and I have a spare one from a Grundig tape recorder. I will contact you if I need an acorn valve, though the generator is working at the moment.

Regards
Martin

2nd Sep 2018, 12:45 am	#1
martin.m Hexode Join Date: Mar 2018 Location: Bishop Auckland, County Durham, UK. Posts: 373	Testgear Acton signal generator I have just acquired a "Testgear Acton" signal generator. Am I correct in thinking that the miniature valves are ex military types? There are two of them, along with an EM81 "magic eye". I have tested the generator (not very scientifically) by connecting a short length of wire to the output socket and placing a transistor radio nearby to pick up the RF signal. All seems to be working from the LW band right up to VHF. Just out of curiosity, how could a vintage signal generator like this be set to an exact frequency? Attached Thumbnails __________________ Regards Martin Last edited by martin.m; 2nd Sep 2018 at 12:55 am. Reason: Grammar

2nd Sep 2018, 1:06 am	#2
Herald1360 Dekatron Join Date: Feb 2007 Location: Leominster, Herefordshire, UK. Posts: 16,536	Re: Testgear Acton signal generator The valves are "Acorn" types- military surplus for sure! Exact frequency setting- with difficulty back in the day! Maybe use a crystal referenced wavemeter like BC221 (also surplus!). Or compare with nearby frequency known station then extrapolate using the scale. Calibration would probably be good enough for simple radio alignment activities though. __________________ ....__________ ....\|____\|\|__\|__\_____ .=.\| _---\__\|__\|_---_\|. .........O..Chris....O

2nd Sep 2018, 1:11 am	#3
Sinewave Octode Join Date: May 2016 Location: Oxfordshire/Bucks borders, UK. Posts: 1,604	Re: Testgear Acton signal generator I set mine with a frequency counter. __________________ Avometer, vintage Fluke and Marconi collector. Also interested in vintage Yaesu and KW.

2nd Sep 2018, 6:45 am	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,899	Re: Testgear Acton signal generator Most probably the valves are 954 with the top connector and 955 the one without. This was a small manufacturer making things out of the mountains of surplus parts on the market in the 50's and into the 60's. The accuracy was whatever it was and most users lived with it for fixing radios. You'll find things like this with user-added marks on the scales where it's been checked against known stations as a guide to making corrections. The frequency meter of the period was the surplus BC221 which is a precision VFO with circuits to allow beats between it and a crystal oscillator to be heard in headphones so it can be trimmed. Each one had an enormous book of its individual dial reading to frequency table - which was printed in an automated test setup at the factory. The output amplitude of sig gens like this one won't go low enough or be at all known enough to check receiver sensitivity, it's really a machine for getting dead receivers going and with care is good enough to align LW/MW domestic sets. The acorn valves mean it's better than many at the top end of its frequency range. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

2nd Sep 2018, 8:31 am	#5
turretslug Dekatron Join Date: Nov 2011 Location: Surrey, UK. Posts: 4,398	Re: Testgear Acton signal generator The perspective makes it difficult to be certain, but that tuning capacitor with its one wide- and two close-spaced sections may be a surplus spare for the R1155 receiver. The characteristically waisted Sprague paper capacitors are likely US surplus (as paper capacitors, they're not above reproach but they are held to be better than many of that ilk) and the generator as a whole is an excellent snapshot of the mountain of surplus components in the wake of WW2. Those ceramic acorn valveholders are kind of rare nowadays- though no doubt some functionary consigned umpteen zillion to landfill at some point.... Fingers crossed that the EM81 still has some go in it. As mentioned, should be a useful first-line checking device, if not lab-standard for frequency and level, Colin

2nd Sep 2018, 7:00 pm	#6
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Testgear Acton signal generator Hi Martin, I probably have spare vales/ magic eye if you need them. Ed

2nd Sep 2018, 10:50 pm	#7
martin.m Hexode Join Date: Mar 2018 Location: Bishop Auckland, County Durham, UK. Posts: 373	Re: Testgear Acton signal generator Thanks to all who have replied. I love old technology and will enjoy using this generator. Ed, thanks for your kind offer of spare valves. The EM81 seems bright enough and I have a spare one from a Grundig tape recorder. I will contact you if I need an acorn valve, though the generator is working at the moment. Regards Martin