Megger ET3

[wireman]

I purchased one of these a while ago as I was interested in having some sort of wind-up instrument to add to my small collection of old test instruments. Came in a very nice leather case.

It can measure earth resistance (not that practical for me as you need to measure over quite some distance) and just resistance.

I have a couple of questions in relation to this which I hope someone can answer.

First the centre 4mm binding post is jammed and I'm nervous of forcing it too much. Is there a standard way to loosen these? I'm assuming a bit of oil and pliers around a cloth.

Secondly the circuit diagram I easily found online mentions a 'mechanical rectifier', would this just be moving contacts geared to the generator?

So far I have just tested it on a 12R resistor to see if it works.

[Silicon]

'Pliers around a cloth' is far from ideal.

I would prefer to wrap the terminal in Gaffer tape and then use an Adjustable spanner.

But first put Penetrating oil or WD40 on the threads. Gentle heat could help.

[high_vacuum_house]

I would prefer to use a not too stretchy rubber belt or similar if you have one, wrap it around, squeeze it to hold it and then turn. Same principle as the stuck kitchen jar opening tool. No chance of scratching the Bakelite knob with metal implements.

Christopher Capener

[wireman]

Originally Posted by high_vacuum_house

I would prefer to use a not too stretchy rubber belt or similar if you have one, wrap it around, squeeze it to hold it and then turn. Same principle as the stuck kitchen jar opening tool. No chance of scratching the Bakelite knob with metal implements.

Christopher Capener

That's a good idea, I do have one of those strap tools where the rubber strap fits into a groove in a handle. I will give it a go at the weekend.

[wireman]

Didn't close the loop on this one.

Small amount of WD40 and using a thick rubber strap 'wrench' worked a treat.