[Collins] Another 516-F2 PS Question

[Dr. Gerald N. Johnson]

That capacitor resonates the choke to 240 Hz for ripple rejection. It 
doesn't do much for the regulation and unless the choke has a huge air 
gap, it probably isn't as effective for 240 Hz rejection as the 
designers wished because an iron core filter choke changes inductance 
considerably from the DC in the coil. Some filter chokes were called 
"swinging" chokes that planned on that effect to have larger inductance 
at low current and lower inductance at high current which improved the 
voltage regulation with varying load.

In most power supply designs the filter choke and filter capacitors 
being more effective at 240 Hz than 120 Hz were pretty good at keeping 
the DC clean. You may notice a bit more ripple without the capacitor 
across the choke, but with the effect of DC current on the inductance, I 
think it will work fine without the capacitor.

In his KWM-2 book, W5USI recommends that capacitor be rated at 1600 
volts with silicon rectifiers.

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association.

On 11/10/2015 3:33 PM, Al Parker wrote:
> Hi Folks,
> I just found out why my 516F-2 was putting out about 1400vdc. C1, the
> 0.05 at 1kv cap across the filter choke was shorted. Thus, I had a
> capacitor input "filter" with no inductance or series resistance.
> IIRC that cap is to resonate the choke when using 60c AC input. The note
> on the skem says to remove it if the line freq. is above 60cy.
> Question, how much affect does it have on the output voltage or
> filtering? I don't have a 0.05 at 1kv cap in stock, but could series 2
> .1 at 500's. But what difference would there be if I left it out?
> any thoughts would be appreciated
> 73,
>
> Al, W8UT
> www.boatanchors.org
> www.hammarlund.info
>
> "There is nothing -- absolutely nothing -- half so much
> worth doing as simply messing about in boats"
> Ratty, to Mole
>