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Old 2nd Nov 2018, 9:21 am   #137
1100 man
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Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
Posts: 1,377
Default Re: Help needed restoring a Murphy V310

Hi Dave,
As I discovered, the oil acts as a very good insulator! That joint at EHT potential would certainly arc to the case in free air but is obviously designed to be fine in the oil. Considering on my transformer, the input to the overwind is only 2mm from the core, that must usually be OK when insulated by the oil.

The plan for mine, when I've managed to repair the overwind and put the transformer back together, is to suspend the whole thing in a clear container filled with cooking oil. I can then hook it back up to the chassis with temporary wires and observe any discharges within the pot. I've got a beer glass that looks to be the right diameter for the job!

I wonder why the overwinds are so different between the two transformers? My one is the same size as the whole primary winding and still only measures 42 Ohms, yet yours is tiddly and manages 136Ohm! They must both generate the same voltage.

All the best
Nick
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