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Old 28th Aug 2017, 11:39 pm   #48
1100 man
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Join Date: Apr 2016
Location: Ventnor, Isle of Wight, & Great Dunmow, Essex, UK.
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Default Re: And the next one! a GEC BT2147

Hi Matt,
Worst case, assuming all the current went through the primary of the transformer via the anode of the shorted valve and through the 1.1K cathode resistor, If the HT is about 200V, then the current through the resistor and primary would be roughly 160ma. I would imagine the transformer would probably handle that OK for a short time so hopefully hasn't suffered. The poor resistor would be trying to dissipate some 30W or so and would fry instantly!!
Measure the primary resistance and make sure it's something sensible (probably 150-200 ohms or so) rather than dead short!
And throw that valve away before it destroys anything else!!
It's also worth disconnecting the frame coils and making sure there is continuity through them. While they are disconnected, measure the resistance of the frame transformer secondary- should be a couple of ohms or thereabouts.
Hope that helps,
Cheers
Nick
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