[AMPS] 4cx5000

[Rich Measures]

>
>Just a aquired a surplus 4cx5000 rf deck and power supply which is odd 
>ball volts and frequency, looks a like a aircraft amp.
>I need to build a 7500 volts 2 amp pwr supply. What is the most suitable 
>approach? 

€  For mine, I used a 3000Vrms Peter W. Dahl 68-pounder, which I potted 
with laminating resin as per the info on my Web site.  I used a FWD.  No 
load was 9100v.  Transmitting on SSB, the supply delivered c. 7800v.  

>.  Where do you get 30000 volt 2 amp diodes, 

€  For a FWD, the actual piv is a bit under 10kV per leg.  15kV total per 
leg would provide a 50% safety factor.   Mount 2 x 15 1N5408s on a 
perfboard, sans-"equalizers", sitting in the air stream and you have it.  
. 1N5408s go for about 20 cents each these days

> and is a C filter suitable with this size power supply? 

€ Sure, for ssb and cw (by switching to a FWB -- ckt on my Web site).  
However for RTTY and FM, a resonant-choke filter is way better.  The 
thing to keep in mind with C filter supplies is that the peak mains 
current is about 10x that for a similar resonant choke supply.  Thus, you 
gotta use huge wire to the mains breaker box with a C filter.  For a Dahl 
68 pounder, #4 copper is adequate for up to c. a 30m run.  ( notes /  
Dahl's 68-pounder has a bar-stock primary winding with c. 0.078 ohms of R 
 /  To covert Dahl's "vA" rating to ssb pep watts out, multiply by c. 3, 
).  

> Also what minimum C should be used

€  I would use (2 x 11) 470uf, 450wv, 105 deg C Panasonic filter caps 
mtd. on an acrylic or g10 sheet with silicone rubber adhesive.  Panasonic 
100k-ohm, 3w resistors work well as equalizers.  //  If you could swap 
for 4cx10,000D, the  difference is a more efficient anode cooler.  This 
would allow you to use a 1700 rpm blower instead of a much more noisy 
3400 rpm blower. 
>.....
-  later, Bill


Rich...

R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures  


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