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high_vacuum_house 8th Oct 2019 10:20 pm

Series 2 Megger insulation and continunity tester
2 Attachment(s)
Good evening,
Not really a restoration but a repair and tidy up. This was bought from a radio rally earlier this year for nearly nothing as it didn't work.
After removing the rear cover which holds the meter movement, it could be seen that the aluminium band holding the magnets to the generator had come apart and there was a nut and bolt missing from this. The magnets had come adrift from their location.

I desoldered the generator wires and removed the 4BA nuts which hold the generator, gearbox and clutch assembly. I found with a small brass bolt and a cable tie, the aluminium band and magnets were reattached back to the generator. This gave a decent clamping force. Testing with a voltmeter showed that the generator was working correctly and was generating 1015V with the clutch slipping so very close to the rated 1000V it was to generate.

I found that 3 of the wirewound resistors had failed. 2 were 100K and in series and I had some high stability metal film resistors to replace these. The other was unusual value of 66700 ohms and a replacement was made up of a 62K and a 4.7K resistor in series.

With these resistors fitted the megger then worked. I reassembled the meter movement into the case and tested the calibration and it was spot on at various points along the scale both the low resistance range and on the insulation test range.

I found a inspection card pinned underneath the meter movement which showed the manufacture date of 16 January 1956 and final test of 20 January 1956 inside so very easy to date !!

The external parts of the case were cleaned and although has some scratches and chips, I think that it would spoil its appearance if I were to strip and repaint it to look like new.

I find these hand wind meggers ideal for testing valve radio/television capacitors, transformers ECT. as they test leakage under reasonably ideal high voltage conditions

Christopher Capener

Herald1360 15th Oct 2019 11:08 am

Re: Series 2 Megger insulation and continunity tester
They're certainly good for the radio related stuff as you say, but no more so than more recent battery operated testers like my Robin 3111V.

Not needing 8 AA batteries is a plus, though two handed operation less so.

Barnmead 18th Oct 2019 11:17 pm

Re: Series 2 Megger insulation and continunity tester
Good to know you got it going and that you have a date can you let me know the serial number so I can amend my webpage if necessary?

high_vacuum_house 27th Oct 2019 10:16 pm

Re: Series 2 Megger insulation and continunity tester
1 Attachment(s)
Good evening,
As requested here is a picture of the meters calibration, test and inspection card. It is held in a pocket under the scaleplate with a small flat spring. Final inspection 20 January 1958. A nice little bit of history there. I will have to see if my others have got a calibration card.

Christopher Capener

Barnmead 28th Oct 2019 10:40 am

Re: Series 2 Megger insulation and continunity tester
Thank you, the serial number fits in nicely with my limited list. The calibration cards seem to be a rarity but I would like to know details if you have more.

Uncle Bulgaria 29th Oct 2019 2:02 pm

Re: Series 2 Megger insulation and continunity tester
I'd like to get one of these! Congratulations on a good job. How satisfying to get things working because of obvious faults, and so long after they were last tested, too.

It's a shame the proud metal plate with maker's name and details has gone out of fashion. I suppose it's considered an unnecessary expense on a product that is assumed to be obsolete in a few years...

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