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Davewantsone · 24th Jan 2019, 5:20 pm

This is because if an internal short in a valve or when faultfinding the HT voltage could be applied to the LT supply. 1N4001 only have a PIV of 50V, 1N4007 of 1000V. The HT could be over 100V so a short-circuit could blow a 1N4001 diode allowing full HT across the valve heaters and zap the lot!

24th Jan 2019, 5:20 pm	#14
Davewantsone Hexode Join Date: Dec 2011 Location: Wigan, Greater Manchester, UK. Posts: 291	Re: Roberts R66 diode MR2 This is because if an internal short in a valve or when faultfinding the HT voltage could be applied to the LT supply. 1N4001 only have a PIV of 50V, 1N4007 of 1000V. The HT could be over 100V so a short-circuit could blow a 1N4001 diode allowing full HT across the valve heaters and zap the lot!