[Amps] HV lytic max V ratings..some notes

Thu Apr 15 07:49:43 PDT 2010

> Date: Wed, 14 Apr 2010 09:27:50 -0400
> From: "Carl" <km1h at 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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