View Single Post
Old 8th Oct 2019, 10:20 pm   #1
high_vacuum_house's Avatar
Join Date: May 2003
Location: Rugby (home) and all over the country for work
Posts: 1,319
Default Series 2 Megger insulation and continunity tester

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
Attached Thumbnails
Click image for larger version

Name:	Megger 1.jpg
Views:	200
Size:	79.8 KB
ID:	191546   Click image for larger version

Name:	megger 2.jpg
Views:	172
Size:	56.2 KB
ID:	191547  
A proper radio is one that needs to be moved with a wheelbarrow !!
high_vacuum_house is offline