Quote:
Originally Posted by ms660
Quote:
Originally Posted by TheMightyMadman
I'm actually even starting to think that the 1W rating that I've ordered will be too much, as if the service manual is claiming a 75mA normal draw from the HV, then power dissipation for the resistor itself is 0.075 * 0.075 * 22 = 0.124 W (approx. 1/8 W).
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The current flowing through the surge limiter resistor will be considerably more than the DC current supplied to the load, that's due to the nature of the rectifier circuit (capacitor input filter) eg: the rectifier is directly connected to a large value capacitor (the reservoir capacitor) as a result of that the current flowing through the rectifier and the resistor will be in the form of a high peak current pulse of relatively short duration, the RMS value of that current will far exceed the DC current supplied to the rest of the receiver.
A good rule of thumb is to double the value of the HT current and use that to calculate the power dissipated in the resistor.
Lawrence. |
Thanks Lawrence
In that case, I'll bump up to a 0.5W resistor for R27.
I've bought some original-style chicken-head knobs for the front controls, and they look far better than the ones that were on there before!
Everything has cleaned up quite nicely.
https://www.ebay.co.uk/itm/155130820342
