[Hallicrafters] SX28 power transformer.

[Mike Everette]

To reiterate:

The SX-28 power transformer is 580 volts center tapped, at between 160 and 180 milliamps.  The B plus voltage in the radio runs around 245 volts if memory serves.

The big honkin' push pull output takes a lot of current.

The power supply choke in the 28 is rated at about 110 milloamps.  This is lower than the transformer rating, because the B plus for the audio PA is taken off BEFORE the choke.

When I referred to GE TV transformers I was thinking of one that I pulled from a late-50s or early-60s vintage set; the high voltage winding was about 590 volts -- low by TV tranny standards -- but the current rating was at least 200 milliamps.

Finding such a TV today is admittedly problematic, but there are lots of them still around if you know where to "dig."

Be aware that the transformer's insulation, and the leads if fabric covered, may have dried out and become brittle.  I recommend sending the iron to be refurbed by Gary Brown (on this reflector).  He does great work and is reasonable.  Hot-tanking and megger testing for a tranny that size would not be too expensive and he might replace brittle leads for a little bit more.

The Hammond transformer someone cited as a replacement, with only a 340 volt secondary, isn't going to do.  Hammond may well make an exact replacement for the 28 transformer; check their lists.

73

Mike
W4DSE

--- On Thu, 4/15/10, Brian Goldsmith <brian.goldsmith at echo1.com.au> wrote:

> From: Brian Goldsmith <brian.goldsmith at echo1.com.au>
> Subject: RE: [Hallicrafters] SX28 power transformer.
> To: "'Mike Everette'" <radiocompass at yahoo.com>, hallicrafters at mailman.qth.net
> Date: Thursday, April 15, 2010, 2:42 AM
> 
> 
> -----Original Message-----
> From: Mike Everette 
> 
> The best replacement, assuming an actual 28 transformer
> can't be found,
> might be an old TV power transformer.  They have
> enough current in the HV
> winding to handle the job, assuming you can find one with a
> secondary of
> 560-600 volts center-tapped
> 
> 
> 
> ****Thanks for that Mike.What B+ current would you expect a
> healthy 28 to
> draw?
> 
> Brian G
> 
>