[Collins] 516F-2

[Dr. Gerald N. Johnson]

On Thu, 2009-08-20 at 00:52 +0930, Lee wrote:
> Hello All
> 
> I looking at the above power supply and was wondering what is the
>  typical ripple voltage on the 275V rail? anyone know?
> 
> 73 Lee

Not much ripple. Circuit analysis based on 60 Hz operation and presuming
there is 280 volts peak to peak ripple (100 volts RMS) at the rectifier
cathode (a convenient number likely there is more like 350 volts peak to
peak), the first choke and capacitor (presuming a good capacitor)
reduces the ripple to 1.5 volts RMS (4.2 volts p-p), and the second
stage filter reduces that to 5.5% of its input or the output voltage
could have 0.8 millivolts RMS or 2.3 mv peak to peak. The ripple will be
higher with old filter capacitors or at 50 Hz. Good exactly on spec
value filter capacitors at 50 Hz would allow 2.1 v RMS (5.9v p-p) at the
first capacitor and 1.6 mv RMS (4.6 mv p-p) at the output filter
capacitor. Fortunately electrolytics tend to be high in value compared
to the label when new. When old they develop considerable series
resistance and allow more ripple voltage. I'd estimate that if the first
stage ripple voltage (with load) was much more than ten volts and if the
output stage ripple voltage was much more than 50 millivolts, its time
for new electrolytics. Using 20 and 40 or 50 uf is not out of line in
place of the 15 and 30 presently there, especially for 50 Hz operation.
-- 
73, Jerry, K0CQ, Technical Advisor to the CRA
All content copyright Dr. Gerald N. Johnson, electrical engineer