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Old July 20th 03, 05:55 AM
Space Charge
 
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Default TX- Power Supply Cap Question

Am overhauling a Heathkit TX-1, came across a previous owner's
component substitution in a Power Supply circuit, and wondered if it
was improper:

It seem that there was originally a pair of 125 microfarad
electrolytic caps (in series,total=250) with a 5.5 Hy 400 ma choke in
back of it, and a pair of 5R4GY's in back of _that_.

The old owner subbed a pair of _200_ microfarad caps for the old,
blown out 125's, maing a total capacitance of 400 microfarads. Now, I
know the traditional wisdom has it that you may go up in replacement
part capacitance value from the old, but that there's a limit on this,
too; too much higher, and you may toast the choke and the rectifiers
over time, as those components ratings may be exceeded by too much for
too long during the capacitor charge-up.

Question: Is 400Uf too much of an increase over 250? Personally, I'd
feel better about sticking in a couple of readily available
off-the-shelf 100's (in series, total=200), and be a bit short, rather
than nearly double the PS filter capacitance....it just seems too
much.

Is there a rule of thumb for this?

Or am I just being too picky?

Tnx to the group in advance,

Lin/KJ6EF
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Old July 21st 03, 11:56 PM
Space Charge
 
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Default

Sorry, guys, about the inane error about series/parallel...this is
what you get for trying to think with a 101 degree temperature. I
just got the mental "A/B" switch flipped to "B/A"!
(series-parallel/parallel -series)"

....and thanks for the input on the solution to what I SHOULD have been
thinking, had I been thinking straight!! Gad. (Ham removes egg from
face, not plate.)

:O

73's DE Lin/KJ6EF
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