[Amps] Shunt resistors for a bridge made of 6A10 diodes in Alpha 91b

[Hardy Landskov]

Steve,
I don't think shunt resistors are needed anymore with today's close manufacturing processes. Someone may have a different opinion.

Also, check the leads that supply the filament current. They go through crimp connectors on the top of one of the pc boards. Mine developed an oxidation which burned up the insulators on the crimp connectors. I replaced the connectors and soldered the connectors and no problems since.
73 Hardy N7RT


-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Steve Ireland
Sent: Wednesday, January 27, 2016 11:32 AM
To: amps at contesting.com
Subject: [Amps] Shunt resistors for a bridge made of 6A10 diodes in Alpha 91b

G’day

I am refurbishing the power supply board in my Alpha 91b and am going to replace the KD202P diodes which make up the bridge with 6A10 diodes (1000V 6A and only A$1.95 each). 

The original bridge had strings of five KD202P a side, with shunt resistors across each diode of 500K 1W. The stud mounted diodes are looking pretty burnt around the retaining washers/bolts, so it is definitely time (and I have a strange earth leakage fault).

Please, I’d really appreciate some advice about what value of shunt resistor to use on each of the twenty 6A10 that will make up the bridge?

PS The replacement encapsulated bridge rectifier sold by Alpha/RKR designs (5kV, 2A) is US$150, so this the reason for looking for a cheaper solution.

Vy 73

Steve, VK6VZ     

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