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

[Jim W7RY]

I've not used equalizing resistors for years. I use 1N5408s and can't 
remember having a failure.

73
Jim W7RY


-----Original Message----- 
From: Jim Thomson
Sent: Friday, January 29, 2016 9:25 AM
To: amps at contesting.com
Subject: [Amps] Shunt resistors for a bridge made of 6A10 diodes in

Date: Wed, 27 Jan 2016 20:31:48 +0800
From: "Steve Ireland" <vk6vz at arach.net.au>
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

##  Dont put  ANY  shunt resistors  across a 6A10.  They don’t need them! 
It’s a series circuit, and the current through each leg of 5 diodes
will be identical..whether frwd biased or not.  Shunt resistors to equalize 
something that is already equalized went the way of the do-do bird years 
ago.
I have been using 6A10 diodes for a long time now.  They don’t requite any 
shunt components..and that includes stuff like .01 uf disc ceramic caps. 
You might want to use
6 diodes per leg,  if they will fit.   The wire leads out each end of the 
6A10 ....IS the heat sink for them, so leave em on the long side if 
possible.   They are typ 1250-1400
piv  when you test them.  The 6A10 is a superb diode. I use it for 
everything from B+ supplies to safety diodes, and also strings of them  for 
bias on GG amps.

Jim   VE7RF

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