Just what I had in the drawers - not a good reason ???>>
Well I worry about two things. First the time to discharge
the caps, but that isn't a concern if you don't care. The
idea is to have the caps bleed off faster than someone can
remove the cover.
Second while caps do tend to self-equalize because the
higher leakage component loads down and reduces it's
voltage, over the long term this tends to reform the better
parts at higher voltage and the parts with more leakage that
can use the most reforming coast along. The 50k value was
picked because it swaps the most leaky to least leaky parts
enough to bring them within 20-25 volts of each other, and
after a while they will all reform much closer.
That was actually part of the testing the boards went
through, although I don't know if they still do.
> I know that for a fact because I wrote the test specs.
Tom, I won't blame you because you are defending your
baby... it is a
normal "mother" reaction...>>
No, I'm just telling you the parts were leakage selected so
if you stick random parts in with more headroom you might
not be doing as much as you think. With a cheap market like
Ham radio it is all about maximizing the cost savings.
It's been years since I looked at this, but as I recall the
life of the capacitor is directly proportional to voltage
(half the voltage twice the life) but is a much larger
multiplier for core temperature of the electrolytic. The
rated hours are multiplied by a formula that includes
voltage and core temperature and the base MTBF time. As I
recall the biggest problem is temperature because it is not
a linear function.
Not to pick on what you are doing, but just to give thought
as to what really happens.
As for the diodes I am very surprised because that is very
uncommon. Capacitors usually fail when a resistor across one
opens or one is backwards. That happens at times, but diodes
and capacitors across them almost never fail.
Fuses are also important. A fuse with a low voltage rating
will sustain current a long time compared to a 250V fuse, so
watch the fuses.
The most common cause of the 10 ohm resistor failing is a
shorted tube.
Yours, since it has unknown history, could have anything
bad.
73 Tom
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