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Greyhill Instruments CR50 Description

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Greyhill Instruments CR50 Description

Post by Michael Watterson » Wed Aug 24, 2011 2:41 am

See ... r50-bridge

I've edited an animation from to run as fast as possible and be the correct orientation for the CR50

I used the "Animation Shop" of Paint Shop Pro 7.

If folks are interested I'll do a construction project of flashing leakage tester for caps that runs on a PP3 yet puts adjustable 45V to 80V on the capacitor. No neon. Uses a 40V transistor in avalanche mode

Or you can have a mains transformer, rectifier and Neon :)

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Post by Michael Watterson » Mon Aug 29, 2011 9:02 pm

Well, that will teach me to "show off" old test gear.

It stopped working, the "eye" lit up nice and green but did not vary on C, Leakage or R ranges.

I suspected the 6SH7. But after running a while it was warm. So heater OK, and otherwise valves don't stop working.

I had a check at the more cheap looking resistors and indeed the 1 M Ohm between Target and "Anode" of the Y63 /6U5G octal eye was open circuit on 47M Ohm max DMM. I'm curious as to why then with target connected and no "anode" it lights up, and not varied by grid?

The 470K grid resistor of 6SH7 and 1M grid resistor of the Y63/6U5G (doesn't say on it) were same kind, so I replaced them too. All the other resistors are expensive looking precision kind and C & R measurements are with 10% on all ranges.  The matching 1M part on the Y63/6U5G "eye" octal base at grid was 950k, which is within spec. I guess those old miniature war surplus composition resistors can just suddenly go open circuit. (They only slightly bigger than modern 1/4W CF).

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Post by Andrewausfa » Wed Sep 07, 2011 6:13 pm

Over the last week or so I've been looking for the methods used for testing wax capacitors at their working voltage. Of course the likelihood is that they all duff but it would be nice to visually see they are!

I've seen the videos posted by Old Goat on YouTube and got rather interested in his Pyramid capacitor analyser with leakage tester, now I've seen your one.  I understand Hunts did one, Heathkit and possibly more US focused manufacturers Sprague and Solar. I imagine coming across one these now would not be something that'd happen everyday.

A construction project, then, would be fantastic if you could spare the time especially, for me anyway, if it's aimed at the ...aahh...not so technical end of the membership. Veroboard, an old tobacco tin and a cycle lamp bulb?

Thanks _Andrew

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Post by crustytv » Wed Sep 07, 2011 6:21 pm

Hi Andrew,

Here is how I test leaky caps on my Hunts CRB 3. Pretty much the same as oldgoat it can apply rated voltage up to 500V, I have a Heathkit IT -28 which can apply up to 600V

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Post by Michael Watterson » Thu Sep 08, 2011 12:04 pm

Flash unit from inside of Disposable film camera?

Likely a pair of AA cells will power it.

Remove flash tube. Put 1M Ohms in series with output. Disconnect Neon from main 350V approx large cap and put a 100nF 350V capacitor (polyester foil, PTFE, Polycarbonate, maybe a Y type) across neon. Remove series resistor of Neon.

terminals are the Neon/capacitor and the 1M Ohm. Short terminals and verify the neon flashes about 10Hz. Put 10M resistor and verify it's about 1Hz.

With a leaky waxy it will flash about 10Hz. With a good capacitor it will not flash at all.

No need to use "flash contacts" as Flash tube is not used. Simply power on with contacts shorted so you see when the main cap is charged and neon flashes.

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