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Heatercathodeshort · 27th Jul 2017, 8:23 am

Removing the actual connections from the overwind will have no effect if it has a s/c turn. To confirm this put a single loop of wire through the core of a working transformer and short circuit it while the receiver is working.
You will have to actually remove the overwind [not possible with the RV10 without destroying it] to make this test.
As Bill has mentioned, check the line drive waveform with a scope if you have one or check for a negative voltage [not quite so conclusive] at pin 2 of the PL81.

If you have any old LOPT from a scrap set, disconnect the line output and boost diode top caps and substitute the same connections on the spare transformer. Leave everything else in place. If EHT is now available at the spare transformers anode connection to the EHT rectifier, it is a good bet that the original has S/C turns.

This is probably why the RV10 was set aside a long while back. It's my guess that a Jellypot or other Thorn transformer would work OK but of course you have to experiment and understand what is happening in the circuits of the RV10 and the donor transformer. Recheck the boost capacitor connections just to be sure. John.

27th Jul 2017, 8:23 am	#37
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Kolster Brandes RV 10 (Crown) Removing the actual connections from the overwind will have no effect if it has a s/c turn. To confirm this put a single loop of wire through the core of a working transformer and short circuit it while the receiver is working. You will have to actually remove the overwind [not possible with the RV10 without destroying it] to make this test. As Bill has mentioned, check the line drive waveform with a scope if you have one or check for a negative voltage [not quite so conclusive] at pin 2 of the PL81. If you have any old LOPT from a scrap set, disconnect the line output and boost diode top caps and substitute the same connections on the spare transformer. Leave everything else in place. If EHT is now available at the spare transformers anode connection to the EHT rectifier, it is a good bet that the original has S/C turns. This is probably why the RV10 was set aside a long while back. It's my guess that a Jellypot or other Thorn transformer would work OK but of course you have to experiment and understand what is happening in the circuits of the RV10 and the donor transformer. Recheck the boost capacitor connections just to be sure. John.