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Heatercathodeshort · 29th Jul 2017, 8:58 pm

OK. This is odd. The test lamp cannot light unless the transformer is being driven at line rate via the PL81.

If you have disconnected the primary and you now have EHT it appears to me that either the scan coils are shorted, [very unlikely but possible] or you have a fault in the wiring.

Check C60 .5uf scan coupling capacitor, the two 40pf 5kv capacitors, C62/C64 for S/C. The later two may be of a slightly differing value. These are 3rd harmonic tuning caps the values of which were adjusted to stabilize transformer 'spread'.

Other than that it may well be the transformer but if the primary has a shorted turn, even when disconnected the circuit would be heavily damped and would not produce EHT. John.

29th Jul 2017, 8:58 pm	#47
Heatercathodeshort Dekatron Join Date: Jun 2005 Location: Warnham, West Sussex. 10 miles south of DORKING. Posts: 9,147	Re: Kolster Brandes RV 10 (Crown) OK. This is odd. The test lamp cannot light unless the transformer is being driven at line rate via the PL81. If you have disconnected the primary and you now have EHT it appears to me that either the scan coils are shorted, [very unlikely but possible] or you have a fault in the wiring. Check C60 .5uf scan coupling capacitor, the two 40pf 5kv capacitors, C62/C64 for S/C. The later two may be of a slightly differing value. These are 3rd harmonic tuning caps the values of which were adjusted to stabilize transformer 'spread'. Other than that it may well be the transformer but if the primary has a shorted turn, even when disconnected the circuit would be heavily damped and would not produce EHT. John.