Thread: Fuses
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Old 19th Dec 2015, 11:33 am   #49
G6Tanuki
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Join Date: Apr 2012
Location: Wiltshire, UK.
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Default Re: Fuses

Fusing heater supplies can be problematic - remember that the heaters have a significantly lower resistance when cold - providing a fuse which offers significant protection while not being vulnerable to the fatigue-failures caused by regularly being run close to fusing-point... OK, you can get slow-blow fuses but I still feel that fusing heaters is likely to compromise the overall reliability of the equipment.

[in equipment with valve rectifiers the first couple of seconds after power-on is likely to see the highest heater-current: not only are the heaters cold/low-resistance, but also until the rectifier(s) come up to emission and start drawing power the power-transformer has no other load on it so can potentially feed quite a bit more than its continuous-rating current to the heaters...]

Fuses in the B+ side I accept (not just one fuse in the centre-tap-to-earth; that won't save your transformer if a diode fails s/c!).
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