"EricM" wrote in message
...
On Apr 14, 9:27 am, "David"
wrote:
I also forgot to mention that the unit in question was
originally 6 -
1 inch square pieces in the stack, but only two
connections. The
other unit that I replaced with the 10A 600V units was
four pieces
about 1 1/8" (or just slightly larger) square, but had
three
connections. This particular unit was on the 15V side
of
the supply
(filament supply for several 12 volt filament tubes)
and
the 600V 10A
silicons seem to work fine. The other part of the
supply
circuit -
the 600V plate supply - is where I used one of the 600V
10A jobs to
replace the 6-stack 1" square two-lead unit. Smaller
but
more in the
stack must have equaled more PIV handling than the 600V
10A silicon I
put where it was (with no dropping resistor). Don't
know
why it's so
hard to find info on these older rectifier units.
They
hadn't gone
bad either, I'm just replacing them to prevent filling
the
cutting
room with toxic stink if they should decide to fail...
I admit I am very confused at this point. The three
leaded
rectifier was actually twoseleniumdiodes with a common
cathode or anode. Your replacement here should work fine
but
check the filament voltage since it will be higher than
before by one or two volts. 12.6 volt tubes will not like
14
volts over a long time period.
There is no way a single 6 plate (stack)seleniumrectifier
can be a half wave rectifier for a 600 volt supply. Each
rectifier plate can withstand only about 50 reverse volts
and as others have said, you need at least three times
that
for a PIV rating.
David
Here's a link to the schematic; after replacing CR1 and
CR2A/B with
10 amp 600 V silicon diodes, when the relay closes to
enable the 600V
plate voltage, the main power fuse F1 blows. I'm not sure
I need
dropping resistors, because the output voltage on the 12.6
and -38
terminals is very close to what it should be. Is there
something I'm
missing?
http://img410.imageshack.us/img410/4691/1567pscb9.jpg
Thanks.
I looked at the schematic and as I suspected, none of the
selenium rectifiers are not involved in the 600 volt supply.
CR2 A&B generate the 12.6 volt filament voltage and can be
adjusted with R1. No problem there. The other selenium
rectifier CR1 is to generate a negative bias supply.which is
also adjustable and further clamped by Zener CR3. The high
voltage is rectified by CR4 and CR5 which, I assume are
silicon diodes that you have not touched. The diodes you
used for the selenium replacement are an overkill but should
not be related to your problem. Are you sure the -38 is
really there and is in fact a minus voltage? If so, at this
point I would check the CR4 and CR5 diodes and other parts
of the 600 volt circuitry to see if you blew something else
when working on this unit.
David