[Amps] Alpha 77 capacitor help

[R.Measures]

On Jun 15, 2004, at 8:55 PM, Martin Sole wrote:

> Some weeks a go I mentioned an Alpha 77 that a friend and I were going=20=

> to
> check out. In examining it we paid attention to the comments made by=20=

> others
> on here about what to look for, in particular the filter capacitor.=20
> What we
> found was a pool of oil under the amp and a greasy film on the diode=20=

> board.
> It will all clean up but the cap is done for we think. Apparently =
Alpha
> power want $800 but they have directed us to Dahl's who still want=20
> $400.
> What we are thinking is that maybe there are alternatives.
>
> Will a suitably sized bank of electrolytics do the job?

=F0  The original capacitor probably started leaking oil after the =
solder=20
seal failed.  This is much more likely when a capacitor that is=20
intended for intermittent flash service is used for continuous duty --=20=

i. e.,  flash caps use thinner foil to reduce size, which increases=20
ESR, which increases I^2 x R loss, which makes more heat, which=20
stresses the seals more due to thermal expansion and contraction.  ----=20=

  I would consider replacing the leaking oil cap with a bank of newer=20
design electrolytics.  A cube of 2 by 2 by 2.  500wv electrolytics=20
should fit into the space occupied by the original cap.  This would=20
provide a 4000wv rating.  Digi-key <www.digikey.com>  2  sells=20
Mataushita/Panasonic 500wv electrolytic capacitors. / see P7456 on=20
p.785 of current catalog for a 30mm x 45mm, 220uF, 500wv unit. =20
However, this mod would require fabricating an assembly of the 8=20
capacitors.  The good news is that the electrolytic cap bank will have=20=

a higher ripple current capability than the original flash cap.
--  good luck, Martin.  cheers
>
> Can oil filled caps be re-conditioned?
>
> Does anybody have something that will do for a 'sensible' price?
>
> Any ideas?
>
> 73
> Martin, HS0ZED
>
>
>
>
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>
Richard L. Measures, AG6K, 805.386.3734.  www.somis.org