Date: Fri, 16 Apr 2010 11:14:11 -0400
From: "Carl" <km1h@jeremy.mv.com>
Subject: Re: [Amps] HV lytic max V ratings..some notes
> ## The ameritrons will do 1.5 kw out, so will qro/command/
> palstar/Emtron. they all have 3.5 kva xfmr's in em.
** Youre starting to sound like someone we know, making up specs on the fly
(-:
Grab a real Dahl catalog and run the math. Example is the Commander 2500
Heavy Duty replacement is 900V @ 2A ICAS. The AL-1200, etc is 2570V @ 800ma
ICAS
### How do u get 1.5 kw CCS, RF output [2.5 kw input, 60% eff] from a 1200 va
CCS
xfmr [Comander 2500] or a 1370 va CCS [ AL-1200] xmfr ??
## My 46 lb dahl is rated for 2750 vac @ 1A CCS = 2.75 kva. All the dahl
46 lb's are aprx the same CCS kva. The next size up is the 68 lb. Then it's
2750 @ 1.5 A CCS = 4.125 kva.
## you are probably correct. The xfmr's in these table top amps are grossly
undersized.....and way over rated. A 46 lb dahl would be the bare min to
use
in any 1.5 kw out RTTY rated amp.
>
>> I can understand 330-560uF
>> which still may place a strenuous starting load on stock amps.
>
>> ## install step start....pretty simple.
>
>
> ** More junk to buy, find room for, and eventually blow unless its
> overbuilt. The Harbach stuff is marginal in a SB-220. Amp Supply uses step
> start in most models.
>
> ## The fix for..'not enough room for step start' is to install it
> outboard.
>>
> ## It's either that.. or fry on/off switch's.. and also cw/ssb switchs.
> Without
> the step start, the peak current is an easy 160-190A through the on/off
> switch..
> albeit for only a split second.
>
** I could also buy a Mini, place it on a custom tube frame and running
gear, stretch the nose and run a blown hemi.
Thats about as ridiculous as adding a bunch of outboard crap to a good
working amp.
## suit yourself. I don't like the idea of frying, and replacing cw/ssb
and also main of/off switch's all the time. I don't like hearing the..
thhhhummmp, when you 1st turn em on either. A ramped up triac
would be another option.. and take up less space. In the meantime,
a small outboard step start box solves all those problems... and also
allows to step start, when toggling between cw + ssb modes. It also
step starts the fils as well. Throw it on the floor, behind the desk. I built
a few of em for fellow's here in town. They operate smoothly. Put as much
C in the Hv supply as you want. A 10 ohm, 100w Arcol /dale metal finned
resistor and 2 x 30A P+B PRD series relays works great.
> ## Then get a Class A ricebox. When toggling between Class A.. and AB
> the difference is just un-real..esp when listening off freq.. with a 2nd
> RX..aprx 4' away. S-9 crud drops to zero.
** I wouldnt waste my money on a new ricebox. Its simple enough to rebias
the TS-940 and add more cooling. Or just use the TS-830. Im less concerned
about HF IMD where Im rarely on SSB except in an already noisy DX pileup. On
VHF and up I take it pretty serious.
## IF you re-bias the TS-940's final PA.... you also have to re-bias the
driver as well.... or ur wasting your time.
>
> ** Some tubes cant take all that stored energy from your overkill caps
> without something better than a glitch resistor. We dont all run YC-156,
> 3CX3000A7, 3CX6000A7, 4CX10000A, and bigger like your crowd do.
>
> ## better imd, far better bang for the buck, rebuildable in most cases.
> You
> can buy any of the above tubes for a lot less, than what it cost to
> re-tube
> a 87-A.
** How does that help the appliance operator that already has an amp?
## It doesn't. It MIGHT provide him with an incentive to hb his next
amp. A $225 YC-156 is a huge bang for the buck.. and no socket required.
No suppressor required either. Just add a surplus 4160/4800 vac pole pig, and
2 x pi nets [ input + output], 2 x meter's....2 x T/R relays and your done.
35w of drive= 1.5 kw. It just goes up from there.
later... Jim VE7RF
Carl
KM1H
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