I saw those listed, nice that RF Parts will warranty them for a year. The
owner had a no-name (Chinese) spare that's in it now. The Eimac had a 94
date code so twenty years of life isn't so bad.
73, Paul
Paul Hewitt
WD7S Productions
QRO Homebrew components
http://home.earthlink.net/~wd7s/contents.htm
-----Original Message-----
From: Carl [mailto:km1h@jeremy.mv.com]
Sent: Tuesday, April 08, 2014 10:32 AM
To: Paul Hewitt; 'Jim Thomson'; amps@contesting.com
Subject: Re: [Amps] HF2500 Power Supply Caps
The Chinese 3CX3000A7 is as good as if not better than the Eimac and about
$850 last I bought. In the 8K they seem bulletproof unlike Eimacs.
Carl
KM1H
----- Original Message -----
From: "Paul Hewitt" <wd7s@earthlink.net>
To: "'Jim Thomson'" <jim.thom@telus.net>; <amps@contesting.com>
Sent: Tuesday, April 08, 2014 12:23 PM
Subject: Re: [Amps] HF2500 Power Supply Caps
> Melt time does not equal stoppage of current flow at these voltages. The
> fuse element is replaced with a low impedance arc that keeps on pumping
> energy into the fault for several AC cycles until the fault clears, mains
> fuse blows or the voltage drops below the level to maintain the arc which
> is
> much lower than the voltage that started it. The fastest fuses are very
> long and filled with sand or other compounds, also pricey. I've seen the
> binding post HB fuse and they have the same problem of slow time. If
> someone thinks these methods are protecting a #40 grid wire in the Eimac
> tubes most of us are using it's a dream. If the target is compliance with
> Eimac's bulletin 17 then this doesn't do it. If better than nothing is
> the
> goal then it's fine. If there really was a fuse that would stop current
> flow in 2ms at these voltages every amp manufacturer on the planet would
> be
> using it.
>
> I pulled a 3cx3000a7 out of an 8K ultra yesterday with a dangling grid
> wire
> causing an intermittent grid to cathode short, ouch. I can buy a lot of
> protection for the $1500 the tube will cost but not my money.
>
> BTW this topic was beat to death on this reflector several years ago, more
> reading in the archives.
>
> Vry 73
> Paul
>
>
>
> Paul Hewitt
> WD7S Productions
> QRO Homebrew components
> http://home.earthlink.net/~wd7s/contents.htm
>
> -----Original Message-----
> From: Jim Thomson [mailto:jim.thom@telus.net]
> Sent: Monday, April 07, 2014 1:34 AM
> To: Paul Hewitt; amps@contesting.com
> Subject: Re: [Amps] HF2500 Power Supply Caps
>
> ## Check out the Buss HVU series of HV fuses...then extrapolate the
> curves.
>
> Then test on the bench
> with a scope to verify that data. BTW, those fuses can easily be rebuilt.
> I have also tried hb hv fuses,
> encased in either teflon spagetti tubing or heat shrink.....suspended
> between standoffs. Then crank up the
> screws tight, in a CW fashion, so there is lots of tension in the fuse
> wire.
>
> ## For folks that want to use a 25 ohm glitch and say a 3 kv supply..
> fault
>
> current is 120 A. Stuff 120 A through
> a 1 A rated fuse...and you will soon see it blows open pretty damn quick.
> Even with a 50 ohm glitch and same 3 kv, the 60A fault current will still
> open up a 1 A rated fuse very fast.
>
> ## You could put the scope across the cold end of the last resistor in a
> HV multiplier string.
>
http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resou
> rces/product-datasheets-b/Bus_Ele_DS_6003_HV_Series.pdf
>
> You can see that with just 4A flowing through a 1A rated HV fuse..it will
> open up in 10 msecs. Now stuff 50-60-120 amps through the same
> 1A rated fuse..and you will measure a LOT less than 10 msecs.
>
> Jim VE7RF
>
>
> -----Original Message-----
> From: Paul Hewitt
> Sent: Sunday, April 06, 2014 2:21 PM
> To: 'Jim Thomson' ; amps@contesting.com
> Subject: RE: [Amps] HF2500 Power Supply Caps
>
> Hi Jim
> I see your posts about high voltage fuses disrupting current in 2ms so how
> about a part number/manufacturer. I would like to see the data sheets I2T
> curves. Most of these fuses open times are measured in seconds and are
> very
> large.
> Thanks &73,
> Paul
>
>
> Paul Hewitt
> WD7S Productions
> QRO Homebrew components
> http://home.earthlink.net/~wd7s/contents.htm
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Jim Thomson
> Sent: Saturday, April 05, 2014 1:29 PM
> To: amps@contesting.com
> Subject: [Amps] HF2500 Power Supply Caps
>
> Date: Sat, 05 Apr 2014 08:41:38 -0700
> From: Bill Turner <dezrat1242@wildblue.net>
> To: amps@contesting.com
> Subject: Re: [Amps] HF2500 Power Supply Caps
>
> On 4/5/2014 8:06 AM, Carl wrote:
>> but more C doesnt buy anything useful.
>
> REPLY:
>
> More C can actually be harmful. In case of an arc, more C just dumps more
> energy into the arc with potentially more damage.
>
> 73, Bill W6WRT
>
> ## With a 50 ohm glitch Resistor installed, the peak fault current
> remains
> the same, regardless
> of C used. However, the 50 ohm glitch + total C will form a RC time
> constant, whose duration
> will be longer when more C is used. With 2500 vdc + a 50 ohm glitch
> Resistor used, peak fault
> current is 50 Amps..... which will easily blow open a 1-2 Amp rated HV
> fuse...and under 2 msecs.
>
> ## The 50 ohm glitch resistor LIMITS the peak fault current. The HV
> fuse,
> just prior, and in series with the
> 50 ohm glitch resistor, INTERRUPTS the peak fault current. You can
> cro-bar
> the supply all day long if you want.
> All that happens is the HV fuse blows open.
>
> ## use whatever size cap you want. The 440-600 uf types work just
> fine.
> The bigger the total C used, the better the
> dynamic regulation of the supply. The ripple is also lower, and in
> proportion to C used. A 600 uf cap will have one third the
> ripple of a 200 uf cap..and way better dynamic regulation on ssb and cw.
> Your load line is not all over the map.
> Now this all works with the proviso that a 50 ohm glitch R and HV fuse is
> used.
>
> ## As far as regulation goes, you require a plate xfmr that doesnt sag to
> begin with....and big enough ga wire from HV supply back to main 200A
> panel.
> You also require large enough rated relays and
> contactors. Any Z between main panel and plate xfmr
> will create V drops..which is bad news with any high C filter.
>
> Jim VE7RF
>
>
>
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