> Date: Wed, 14 Apr 2010 09:27:50 -0400
> From: "Carl" <km1h@jeremy.mv.com>
> Subject: Re: [Amps] HV lytic max V ratings..some notes
>
>
>> ## alpha used 1N4007's in their 374-A no tune.. pure junk. [diodes]
>
>
> ** Dont know of any failure issues. Later models went with the 1N5408 as
> the
> price difference came down to almost nil.
>
> ## 1N5408's were 40 cents each, in 1976. 1N4007's are failure prone.
> Peak rep is way too low, surge is too low. How cheap could they get ?
** At 1000W DC INPUT they were sufficient. Dont forget the rules were
different then. How many SB-220 diodes blow except when a cap lets loose?
Those are only 600 PIV @ 1A and of unknown surge reserve.
** The Alpha 76's all used 5408's so users could ignore the FCC and run
1200-1800W out on SSB and CW. The Dahl xfmr was an option.
>>
>> ### I can hear the diff with ESSB. I can also hear the diff on AM.
>> I'm not
>> talking abt 120 hz ripple either. The ESSB audio sounds cleaner.. as
>> does
>> AM audio. I haven't tried FM..yet.
>
>
> ** Then you are in a very small group.
>
> ## agreed. After the yaesu MK-V RX mods, [including bypassing the entire
> yaesu
> AF junk], easy to now hear any defect. I shut off their RX DSP junk as
> well, since it's
> not done right, and adds yet more distortion and...'digital grunge'. The
> stock yaesu
> 1.5 w @ 15% THD AF amp is a joke. Ditto with headphone amp. I tap off the
> Analog
> RX product detector.. then straight out externally.. to outboard Class A
> audio amps.
> As a side note, the stock yaesu MK-V, TX DSP is more crap... the noise
> floor increases by
> 21 db, when toggling between Analog SSB.. and DSP SSB. [mic gain on zero]
>
>
>
>
>>
>> ### say what? The alpha's all have a 3.5 kva CCS xfmr... and so does
>> the AL-182/1200/1500. So does the ten tec centurion.
>
>
> ** Say what?? You better get your glasses on and read an old Dahl catalog.
>
> ## any 1.5 kw CCS out amp with 50-60% eff... will require a bare min
> of 3000-3500 va ccs xfmr. You can buy the alpha 3.5 kva CCS xfmr,
> as used in all their recent amps, including the 91/99/87A..from their
> site.
** I wasnt talking about those later amps. I stay far away from
microprocessor crap.
>
>
>>
>> ## so what's wrong with big C filters then? You can buy surplus big
>> 2300uf + caps for the same price as new 330uf to 560 uf vcaps. An
>> extra FREE
>> 100-200 w pep out and better imd, is nothing to sneeze at.
>
>
> ** Eimac didnt use ridiculous amounts of C to establish tube specs which
> are
> usually well above the crap SS rigs in use. 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.
>
>>
>>
>> ## P-P voltage drops from 210 V.... down to just 16.8 V P-P
>
>
> ** I never saw a Drake with only 210V PP drop. The iron is only .8A CCS.
> Thats .4A after it is doubled which is half PEP Ip.
> What does it do key up-key down?
>
> ## Lemme re-phrase that. With a 800 ma DEAD CXR... the PEAK to PEAK
> RIPPLE, is 210 V. That's with stock 25 uf filter cap. [200uf /8]
>
> ## With 312.5 uf [2500/8].. and the same 800 ma dead cxr, the PEAK to
> PEAK RIPPLE is now 16.8 v Dyanamic regulation is superb.
>
> ## B+ is 2650 vdc on RX... and drops to 2605 vdc, when sucking 145
> ma
> ZSAC. B+ drops to 2485 vdc.. with a 800 ma CXR. This is with stock
> 25 uf
> filter cap. That's using both the built in B+ meter, on all 4 x drakes..
> and also
> a Fluke 0-6kv dc HV probe and a fluke 87 DVM. Now with a 50 ohm-50W WW
> glitch installed, with a 800 ma cxr... B+ drops another 40 vdc [.8 x 50
> ohms]
> .... and B+ is now down to 2445 vdc. This case is with 25 uf stock
> filter.
> With 312 uf, all numbers are up by 28 vdc. [800 ma cxr] On SSB, B+ meter
> barely flicker's.
** I still say it buys you nothing for normal SSB as long as the caps are
fully functional. If its not audible its not a problem. I only care about
perfection in a woman.........
>
> ** I still have the 51.5UF @ 10kv Sangamo on a bottom shelf for some
> future
> project. I believe it is over 150# but its been 20 years since I moved it.
> I
> couldnt store wimpy lytics that long.
>
> ## kinda tough to stuff a 150 lb cap into a MLA-2500. 51 uf isn't big
> enough anyway. Heck, even Emtron figured it out.. and used 112 uf.
> A 2500 uf cap weighs 14 oz. 10 A ripple current rating.
** My backup MLA2500 has 330uF Snap Ins. More than enough, run cold and dont
have to be outboard in a plywood box. 8873/74/75's have at least 10-15dB
better IMD than any Class AB rice box, they dont need any more.
** The Alpha 76 3 holer on the 2nd TS-940 still has stock caps. So does the
LK-500 on the other 940 but I'll be replacing with 470 or 560uF soon since
it already has a step start.
>
> ** Meanwhile most of us are grounded in the real world and happy with
> using
> 270(current Ameritron stock)-560uF during replacement time since they at
> least fit existing amps.
>
> ## stuff the biggest caps that will fit into these desk top amps!
> 270/8= 33.75 uf = 151 joules [3 kv] 1 joule = '1 x watt second'
> 1.5 kw out at 60% eff requires 1500/.6 = 2500 watts DC input. If you only
> have
> 151 joules of energy stored up, no wonder the B+ sags on ssb! A stock
> SB-220
> is even worse with it's 25 uf = 112 joules.
> 315 uf @ 3 kv = 1406 joules.... no sag on ssb... and way more pep out.
> Instead of knocking the concept, maybe you should try it. Better dynamic
> regulation
> was the primary goal. The reduced ripple was a secondary benefit. End
> result is more
> pep out, less IMD.
** Ive said several times on here and elsewhere that 330-560uF is fine IF it
fits and IF a step start is used. For some amps its not a practical swap due
to available room.
** 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.
** RCA specifies right on the 8122 spec sheet that above 2200V no more than
10uF output C be used. Thats what the NCL-2000 used with 8X 80uF. My 6M
version now runs 41.25uF ( 8X 330uF) with no damage yet. But the glitch
resistor has gone from the stock 15 Ohms (Yes a glitch resistor in 1963,
long before Measures and Rauch invented it) to 50 Ohms which doesnt help the
regulation. Ive retrofitted a few customer NCL's with 8X 220uF and 25 Ohm
glitch.
** I wonder how much the Svetlana bogus HV rating for the GU-74B and big
caps used in the amps has contributed to the seemingly high failure rate?
Carl
KM1H
>
> later... Jim VE7RF
>
>
>
>
>
> Carl
> KM1H
>
>
>>
>> Jim VE7RF
>>
>>
>>
>>
>> Carl
>> KM1H
>>
>>
>>
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