[Hallicrafters] Ref: SX28 xfmr

[Carl]

The 80/5Y3, and the 5Z3/5U4 are virtually identical specs.  A 5R4 may be a 
reasonable substitute for most 5U4's to save 5W of filament power.

However dont expect swapping a rectifier tube for SS to reduce transformer 
heat by the amount of filament power.

If you want a cool running radio use a bucking transformer to drop the input 
AC to 110-113V.

Carl
KM1H



----- Original Message ----- 
From: "Roy Morgan" <k1lky at earthlink.net>
To: "Walt Cates" <cateswa at msn.com>
Cc: "hallicrafters" <Hallicrafters at mailman.qth.net>
Sent: Thursday, April 15, 2010 10:07 PM
Subject: Re: [Hallicrafters] Ref: SX28 xfmr


>
> On Apr 15, 2010, at 11:42 AM, Walt Cates wrote:
>> ... I don't know what the current requirements for the 28 are. If
>> 40ma high voltage and 2A @ 5vac and 2A @ 6.3vac will work the
>> HX237AZ is $30 cheaper.
>
>
> SX-28 folks,
>
> The (military) manual for the SX-28A shows:
>
> 6.3 volts at 4.8 amps
> 270 vdc at 150 ma.
>
>
> If such manual information is not at hand, just go through the list of
> tubes and tally up the filament currents and normal operation plate
> currents.
>
> Very rough approximations might be:
>
> The rectifier is a 5Z3, so it's normal operation rating for current
> can be used as a rough guide.
> The radio has two 6V6's in the audio, and they might operate at 30 ma
> each - do ohms law on the voltage at their cathodes and the self-bias
> resistor value.  (So the 40 ma is not enough by a lot.)  IF, RF and
> audio amp tube often run at 8 to 10 ma each, mixers about the same.
> Screen currents might be ignored in an approximation.
>
>
> About rectifiers:
> 5U4's take 3 amps filament (If I remember right)
> 5Y3's use 2 amps but won't do 150 ma I think
> 5R4's use 2 amps but have surprisingly high DC rating
> 5Z3 may be similar
>
> Roy
>
>
>
> Roy Morgan
> k1lky at earthlink.net
> 529 Cobb St.
> Groton NY, 13073
> Home: 607-898-3607
> Cell: 301-928-7794
>
>
>
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