[Hallicrafters] SX-28A Recapping

[W1gfh at aol.com]

Mike, I recapped all but the RF deck in my 28A and it's purring along fine.  
While you are in there you might want to check the various power resistors 
(anything over 1 watt) and replace them if they look "iffy".  - Joe, W1GFH

*Below is an email I got from Jeff Anderson a while ago regarding the same 
issue. Reading his insights might be of help.

--

When I received my 28A the easy caps had been replaced.  The RF deck had not

been done, and the caps around the push pull audio (obscured by P/S caps,

P/S choke, tone choke, and output transformer) were still original brown

waxys.  One of the caps in the push pull had failed, which took out the

output transformer.  That's why I got it cheap.  While replacing the caps in

the audio section, I too looked at doing the RF deck, but decided that it

was more of a project than I wanted to tackle.  Within six months one of the

screen bypass caps in an RF amp had failed, so I was left with no choice.

I don't believe that there is any easy way to do it.

On the top side, all the connections to the tuning caps must be removed of

course, and on the IF side of the deck, each of the 'modules' has 4

connections at feedthru terminals down near the screws.  Less obvious is

that most of the modules have at least 1 wire coming out through a grommet

on the P/S side that connect to different points to deliver high voltage to

the modules.  Also, most of the modules have a wire or two that pass through

grommets from one module to the next.  These are the tough ones.  As I

recall, most of them can be reached, marked, and carefully unsoldered from

the band switch.  In at least one case, I cut the wire rather than

unsoldering it from the terminals on the RF coils, and repaired it later.  I

was afraid of damageing the coils during desoldering.  Once the wires are

all undone, and the shafts removed, the modules will come out.  I believe

that I started at the rear of the receiver (1st RF), and worked my way

forward.

There are caps down in there that you can't even see without removing the

modules.  While replacing the caps, I checked all the resistors and found

that very few were within 20% of their original value.  In the end, I

replaced all the caps, and all the resistors.  I also tested and replaced

many resistors in the rest of the receiver as well.  If you choose such a

radical course of action, I would recommend trying to duplicate the original

component placement as much as possible.  Due to short leads on some of the

replacement parts, I neglected this, and had some problems due to signal

coupling.

But when it was all said and done, it was a totally different receiver.

Very sensitive, fairly selective, with nice audio.  The tuned frequency

still drifts terribly, and the top band doesn't work due to a bad coil in

the first RF amp (that's what I got the replacement deck for).  Both of

these problems will require that I pull the RF deck again, so I'm in no

hurry, but I really like this radio.

As far as advice... It's a hard job.  If the radio works as it is, I would

probably wait.  But brown waxys fail, and if you wait (and use the

receiver), you will probably get your chance anyway.  As did I.


Good Luck, and I hope some of this rambling helps.

-- Jeff


>Today I completed the "recapping" process on my SX-28A. Well, okay, I've
>done all of the easy to get at ones, 24 to be exact. Now for recapping
>in the RF compartment. I have read "Phils Old Radios" section on his 
adventure
>in doing an SX-28. Can anyone tell me if the 28A is easier to recap than
>its 28 counterpart! Sheesh, I'm thinking they are probably identical in
>that aspect and can't wait to rip open the bowels of my beloved rig (NOT)
>and unsolder all of those wires, take out all of those screws, disconnect
>the bandswitch and antennae trimmer shafts (now I'm crying). Any suggestions
>and advice aside from what Phil has documented would be greatly appreciated.
>Thank you in advance!
>
>
>
>regards,
>
>Mike Smout