recapping hp-23

[Multi-Volti Devices]

The exact value isn't critical. The solid state rectifiers won't be
critically sensitive to variations in capacitance, even significant
changes approaching doubling, most likely. I say most likely because I
really can't tell you the surge current.

The rated transformer hv winding voltage is 282 V @ some current rating
I don't remember. If you disconnect your bad caps, you could measure the
open circuit (no load) hv winding voltage and multiply by 2.828 (2 x
square root of 2) to get the no load DC value, then give your self some
safety margin for high line voltage (say, a factor of 10%; I believe 132
V is an accepted tolerance limit for most power companies in the US
(ugh...hate to have that at my house), so
for the 282 V (I didn't use the no load value because I haven't measured
it...that's for you to check) see below:

282*2.828*1.1= 877 V

divided across two caps you'd have 438 V, and remember that isn't
considering the no load condition, so you can see why there are 500 V
caps. 450's would probably work for awhile, 'cuz the sky doesn't always
fall right away.

Looking at it from a simpler perspective, 450 plus 10% is 495, so I
wouldn't ignore it.

There are 500 and even 600 V electrolytics available nowadays. New
Sensor (may be difficult to buy from them as an individual, especially
if you're demanding with regard to specs, or any other info ...not
certain, though, and maybe Antique Electronic Supply in Tempe AZ.

Good Luck, and keep your fingers out.


Murray.



William J. Graham wrote:

> I'm looking at recapping an HP-23.  It has 4 125uf 500v electros that
> I'm looking at replacing with 100 uf 450v axials.  2 of them are in
> the LV 250-350v circuit and this doesn't look like a problem.
>
> The other two are in the B+ hv circuit. The voltages shown  don't look
> to
> be a problem but thought I'd get trhe collected wisdom.
>
> I could parallel with 22 uf 450v for clser vaule as well I guess.
>
> Bill
>
> N5LMX/DA1WG
> bgraham at tecnet1.jcte.jcs.mil
>
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