> Date: Mon, 12 Apr 2010 10:17:32 -0400
> From: "Carl" <km1h@jeremy.mv.com>
> Subject: Re: [Amps] HV lytic max V ratings..some notes
>
>
> I dont see anything wrong with a 5-10% variation in the voltage across
> each
> cap in an amp with enough headroom. Individual capacity was all over the
> place 25-50 years ago unlike today where 20% is the normal spec.
>
> As some equalizing resistors do age it is always an increase and rather
> uniform in my experience with the non carbon variety.....thats a reduction
> in heat when they go from 50K to 65-70K as in the NCL-2000 for instance.
>
> The 30K Heaths rarely budge.
>
> ### 30 k ohms is way too low a value. All as you are doing is cooking
> the
> caps.
** Those were the calculated or recommended values (30-50K) used back then.
As tolerances improved resistors increased in value.
The L4PS.. and L7PS used 100 k , 2 watt carbons... and even they look
> new after 30+ yrs.
** Dentron did the same. Alpha used a pair of 220K in parallel.
I put the new 1% tol vishay's in there.. and there is
> variation at all between caps.
>
>
>
>
> I still say that going extreme in filter C is a waste of time in most off
> the shelf amps. Ive yet to hear any audible ripple complaints about
> 80-150uF
> caps used in strings in the old days. Going from 200 to 330uf as I do with
> SB-220 repairs makes only a very slight PEP improvement; the transformer
> isnt capable of more and its the same with many price conscious amps.
>
> ## The SB-220 xfmr is only a 500 VA unit... which is fubar. Big diff
> between
> a 500 va xfmr and a 3.5 kva xfmr.
** Im talking about commercial ham amps. Anyone can go oversize on HB with a
credit card.
>
> ## putting 600uf caps in a AL-1500 does make an improvement. You
> can get em in 500 vdc too. Pep out is up. I'm convinced imd is
> improved.
** As well it should go up. Its no different than the vintage requirement
for a stiff L-C-L-C filter in a modulator PS plus with a stiff bleeder. You
barely see the HV meter move.
>
>
>
> Now if you want to run strings of 2400-4700uF caps with your 253# Dahl
> iron
> on a 3x10 or whatever that is your business.
>
> ## I used 8 x 2500 uf caps on the L4PS.. and B+ doesn't budge on ssb.
** Serious overkill unless you can measure an improvement that is actually
audible. Otherwise it is just bragging material (-;
>
> ## The single GS35B 6m amp,..used the 46 lb mag cap xfmr... and B+
> dropped
> 800 vdc. There was also a 6 vac drop in the 12 ga wire. The 2 x GS35B
> 6m amp
> uses 2 ga wire and a bigger xfmr... and a string of 3900 uf caps. V drop
> is only 150 vdc
> power output is quadruple.
** There is something seriously wrong with that 800V drop. My 2M 3CX1000A7
amp which loafs at 1500W uses a modern 45# E-I transformer and 16uF (or
maybe its 24uF, either 8x8 or 12x12, its been years since I looked) of oil
filled caps. The bleeder draws about 100ma at 3900V idle and at 900ma key
down from the tube the drop is around 250V and that is thru about 50' of
10-3 from panel to outlet and 6' of 12-3 into the PS. Im convinced that real
filter rated oil caps give better regulation.
Carl
KM1H
>
> Later.. Jim VE7RF
>
>
>
>
>
>
> Carl
> KM1H
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