The delay relay closes its contacts which energises the coil of a conventional relay which a: shunts the contacts of the delay relay, thus maintaining itself closed and b: disconnects the heater supply to the delay relay which allows it to cool so that it may be ready to provide another delay if the power is interrupted.
The delay relay therefore drops out of circuit immediately it closes. It should not drop out with a 'big spark' thirty seconds later.
Richard.
casej451 wrote:
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As far as I know there is only one delay relay. It kicks in after
the tubes have had a chance to warm. The only time mine ever kicked
out was when the thermal protection tripped, which it will do fairly
quickly without the fan, with the cover off.
