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Vintage Telephony and Telecomms Vintage Telephones, Telephony and Telecomms Equipment |
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7th Dec 2020, 1:20 pm | #1 |
Heptode
Join Date: Apr 2010
Location: West Midlands, UK.
Posts: 659
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GPO Tester for what purpose?
Does anyone know anything about the tester pictured? The label on the lid says "Tester RP1100 DGM RPW 1100/1B, the rotary switch is marked in mA/V, the meter is an unusually scaled 25-0-250 uA one. There are 2 push buttons on the side for zeroing and measuring, 2 input terminals and a compartment for a 1.5 volt battery underneath.
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7th Dec 2020, 2:16 pm | #2 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,188
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Re: GPO Tester for what purpose?
From what I can discover, it's a special-purpose valve tester used to test the valve in a 'panel amplifying 32'. It's connected across the cathode resistor of the valve, you then 'set zero' to balance the normal valve current (similar to backing off in the AVO valve characteristic meters), then press the measure button which shunts the cathode resistor with a resistor in the tester and thus changes the operating point of the valve. Adjust the mA/V control to get back to zero on the meter, then read off the mutual conductance of the valve.
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7th Dec 2020, 3:41 pm | #3 |
Heptode
Join Date: Apr 2010
Location: West Midlands, UK.
Posts: 659
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Re: GPO Tester for what purpose?
Thanks for that information, Tony, there is a scratched on marking "min" at the 1.5 mA/V
setting. Do you have any further info on the panel or the type of valve used? Mike. |
7th Dec 2020, 3:55 pm | #4 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: GPO Tester for what purpose?
Is there a model number - e.g. on the paster diagram? Unfortunately, the resolution isn't sufficient to read the text at the top left.
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7th Dec 2020, 4:12 pm | #5 |
Triode
Join Date: May 2014
Location: Worcestershire, UK.
Posts: 37
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Re: GPO Tester for what purpose?
Tester RP1100 DGM RPW 1100/1B according to the OP.
Amp 32 was a little before my time, but IIRC they were 27dB gain and reasonably flat to around 6kHz. |
7th Dec 2020, 7:50 pm | #6 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: GPO Tester for what purpose?
Whoops! Yet again I overlooked the relevant information.
Anyhow, a search of the Telecommunications Heritage Group web sites for RP1100 draws a blank.
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Mending is better than Ending (cf Brave New World by Aldous Huxley) |
7th Dec 2020, 10:18 pm | #7 | |
Heptode
Join Date: Jul 2007
Location: Flintshire, UK.
Posts: 707
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Re: GPO Tester for what purpose?
Quote:
TESTER RP1100 For testing Valves CV 1343 on Panels, Amplifying No 32. Dgm RP1100 Portable. (EI TRANSMISSION, Tele, F 1053) One place I looked after, deep underground, had racks of Amps 32 all full of valves with paper labels giving the exact date they were fitted - 99% were c1937 when the place opened - I'm told they were expecting a Mr.A Hitler ? |
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8th Dec 2020, 12:47 am | #8 |
Nonode
Join Date: Oct 2014
Location: West Midlands, UK.
Posts: 2,181
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Re: GPO Tester for what purpose?
Rings a bell in my memory, as the standard pre 51 type pane Audio Amp fitted in TRS to amplify 2w audio circuits, with I seem to remember 30 dB gain). I never used this tester as a better test , was to measure the cathode voltage and compare it to a set value, almost as in checking the CV voltage on 51 type panels. Below a set voltage and best guess was a valve change. After that it was fault the amp( or re jumper it for a good one and fault later, and expect fingers hit with 230 v). .
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8th Dec 2020, 5:33 am | #9 |
Dekatron
Join Date: Jun 2015
Location: Biggin Hill, London, UK.
Posts: 5,188
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Re: GPO Tester for what purpose?
I think that just shows how broken the search is on the THG member's sites. I did manage to find the circuit diagram and operating instructions on the thgr (BT archives) site.
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8th Dec 2020, 9:03 am | #10 |
Dekatron
Join Date: Feb 2005
Location: West Cumbria (CA13), UK
Posts: 6,118
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Re: GPO Tester for what purpose?
Yes, I would agree that a school report on that function might say something similar to what so many of mine said: "Could do better."
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