[Amps] HF2500 Power Supply Caps

[Jim Thomson]

Date: Sat, 05 Apr 2014 23:15:24 -0700
From: Bill Turner <dezrat1242 at wildblue.net>
To: amps at contesting.com
Subject: Re: [Amps] HF2500 Power Supply Caps
ORIGINAL MESSAGE:          (may be snipped)

On 4/5/2014 1:29 PM, Jim Thomson wrote:
> ##  use whatever size cap you want.

REPLY:

I disagree. Use the smallest cap that will give you the performance you 
need in terms of ripple and dynamic regulation. Anything beyond that is 
a waste and potentially damaging. Not all arcs happen ahead of the 
glitch resistor or the HV fuse.

Good designers are paid big bucks to accomplish the job without overkill 
on parts specs. Learn to be one.

73, Bill W6WRT

##  Install a 2nd HV fuse,  between one leg of plate xfmr sec, either leg, and FWB, or
doubler...and now you have also protected the  diode board.....and plate xfmr.  Install a fast,
magnetic-hydraulic breaker in the 240 vac line..and  your protection is as good as it gets. 

##  The 2nd HV fuse cost dick.  Hows that for a good design ?   Look, I have tried  24 x 10,000 uf caps
on a 7700 vdc supply..and nothing happens with a  B+  to chassis short.   50 ohm, kw glitch used. 
4 x 200 ohm, energy absorbing type globars used in parallel..and air cooled..with a pair of 
10 inch fans.    Each resistor is  1.5 inch  diam x 18 inchs long...all mounted vertically.   All that happens is the HV fuse opens. 

##  600-1000uf caps cost very little these days..so why cheap out ?   Caps are cheap on the surplus market as well.
IMO,  1%  ripple is the minimum that you should be aiming for  in a HV supply.   That implies 600 uf caps vs 200 uf caps. 

## Big difference  between trying to make a profit on a HF2500 amp... vs  upgrading the caps  yourself..after the fact.
How much more will an amp cost if 6A10s are used vs 1N5408s ?   A few bucks at most ?   200 vs 600 uf caps..same deal.
I don’t see commercial ham amps using vac tune and load caps........ too expensive.   Dirt cheap on the surplus market..so for 
a homebrewer,  why not use em ?   

##  Good designers use the bare minimum for any part in the amp to do the job.   I don’t think I would want to run 1.5 kw
rtty  on 160m with an ameritron XXX amp..through an ameriton  XXX  tuner..also on 160m.    Some of this ham junk isnt
designed well at all, nor engineered.... its ill conceived. 

Jim  VE7RF