[AMPS] Alpha 77's

[km1h @ juno.com]

On Sun, 10 Aug 1997 21:37:25 +0000 w8jitom@postoffice.worldnet.att.net
writes:
>> From:          Ron Hooper <ab4ru@stc.net>
>> Date:          Sat, 9 Aug 97 01:49:50 +0000

SNIP>>

>> about 1800 watts out, with one tube. I got to believe the choke is 
>under
>> rated for 2 tubes. 

The stock plate choke is the B&W 800 and was originally rated at 90uh,
500ma, 2500V in the 1975 catalog. By 1985 the ratings were 3500V and
750ma. There was no change in the form or wire size, just the marketing
department. 


>If the choke had excessive dc voltage drop, it would be on fire or 
>glowing red hot...hi.  
>
>>   Now the transformer in my unit is rated at 2.4 kva about the same 
>as
>> the one in my commander.
>
>I gave up on figuring out where manufacturers get their kVA ratings. 
>The AL1200/1500/82 transformer is a 1800 VA CCS core, and it is the 
>highest kVA rated core available for that approximate weight. That 
>transformer weighs about 35 lb

A  full bore AL-1500 at 2400W output is running at 4KW input. The LK-800A
at the same output used a Dahl xfmr at 46 lb. 
I have no idea of the AL-1500 xfmr failure rate but I would suspect it is
very low even when pushed in CW contests, etc. 

 Smaller and lighter transformers are 
>rated higher (Amp Supply sold a 1200 VA core transformer and called 
>it 3 kVA).

And pray tell what Amp Supply amplifier was that transformer used in?
Or do you mean the APS-1 kit he sold for awhile? That used the same Peter
Dahl Hypersil xfmr as the LK-500 series and yes, the ratings were
stretched a bit in the kit advertising only, but not to an unsafe limit
for intermittent SSB service. 
The transformers used inside the amps and external paks were all Dahl and
well rated. Xfmr failure in Amp Supply amps is almost nil. 
  

>In ICAS duty, you can push the transformer. But you'll find the ETO 
>transformer marginal. It uses up too much window area for the low 
>power windings and their insulation, so it has way too much copper 
>loss.
>
>I also think putting the filament winding of a HV transformer, when 
>the PA is out of the low power or medium power class, is not a good 
>idea. It can cause inrush and voltage stability problems in the 
>filament supply. 

I will never understand ETO's reasoning for this. Has anyone measured the
filament voltage swing in a DX or SX with a stock xfmr? 

73....Carl   KM1H


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