FW: [Hallicrafters] Recapping Hallicrafters

[alan doss]

My personnel feelings on using higher Voltage caps is, its ok, the only 
thing that I find is it costs a little more for the higher voltage caps, 
Alan.

>From: "Langston, Mike" <MLangston at HCPRICECO.com>
>To: <Hallicrafters at mailman.qth.net>
>CC: glowbugs at piobaire.mines.uidaho.edu
>Subject: FW: [Hallicrafters] Recapping Hallicrafters
>Date: Mon, 18 Jul 2005 16:30:49 -0500
>
>Just replaced the electrolytics in the HV section of my Apache.
>Originals were (2 ea) 125 mfd @ 450V in series yielding 62.5 mfd @ 900V
>(choke filter). I could only find 125 mfd @ 400V but figured that would
>be OK since they are new "modern" caps. The higher line voltage gives me
>800V on the plate (supposed to be 750V) under load and the caps
>definitely don't like that. Didn't explode, but one got so hot it melted
>the plastic coating and started smelling bad enough that I got the HV
>off it in time (yes, it has equalizing resistors in the circuit). I
>recommend higher voltage ratings in these types of circuits with the
>higher line voltages we see today.
>
>The voice of experience (Mike)
>KL7CD
>
>-----Original Message-----
>From: hallicrafters-bounces at mailman.qth.net
>[mailto:hallicrafters-bounces at mailman.qth.net] On Behalf Of Roy Morgan
>Sent: Monday, July 18, 2005 3:05 PM
>To: Clayton L. Nicolsen; Hallicrafters at mailman.qth.net
>Subject: Re: [Hallicrafters] Recapping Hallicrafters
>
>
> >One mistake some make is replacing electrolytic caps with one of a
>higher
> >voltage, this will accelerate the aging of the cap.
> >
> >I have never heard anyone say this before.
>
>Clay,
>
>I may have said that using an electrolytic at a voltage lower than its
>rating may get you slightly higher capacitance, because the electrolytic
>
>film that forms the actual capacitor is thinner and thus has higher
>capacitance.
>
>Recently, however, I carefully reformed some new old stock can
>capacitors
>and noticed that the capacitance was slightly higher at higher reforming
>
>voltages. And the dissipation factor went down as i reformed them.
>
>I think we should use electrolytics aof whatever voltage we have, as
>long
>as they are not run above their rating, during use or during startup.
>
>Roy
>
>- Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
>7130 Panorama Drive, Derwood MD 20855
>Home: 301-330-8828 Cell 301-928-7794
>Work: Voice: 301-975-3254,  Fax: 301-948-6213
>roy.morgan at nist.gov --
>
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