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Old 7th Dec 2020, 12:20 pm   #1
Gridiron
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Default 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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Old 7th Dec 2020, 1:16 pm   #2
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Default 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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Old 7th Dec 2020, 2:41 pm   #3
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Default 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.
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Old 7th Dec 2020, 2:55 pm   #4
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Default 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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Old 7th Dec 2020, 3:12 pm   #5
198 kHz
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Default 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.
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Old 7th Dec 2020, 6:50 pm   #6
Dave Moll
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Default 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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Old 7th Dec 2020, 9:18 pm   #7
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Default Re: GPO Tester for what purpose?

Quote:
Originally Posted by TonyDuell View Post
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.
I can firm its use from one of my copies the 'Vocabulary of Engineering Stores' -!956'ish edition -

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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Old 7th Dec 2020, 11:47 pm   #8
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Default Re: GPO Tester for what purpose?

Quote:
Originally Posted by 198 kHz View Post
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.
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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Old 8th Dec 2020, 4:33 am   #9
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Default Re: GPO Tester for what purpose?

Quote:
Originally Posted by Dave Moll View Post
Whoops! Yet again I overlooked the relevant information.

Anyhow, a search of the Telecommunications Heritage Group web sites for RP1100 draws a blank.
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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Old 8th Dec 2020, 8:03 am   #10
Dave Moll
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Default 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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