[Hallicrafters] SX-28 RF alignment

[Julian Bunn]

So here is an update on my SX-28 RF problem. I had been
discussing this offline with Rodger, who made several
very useful suggestions.

But last night I decided to go back to basics before
going any further. I attached an aerial to see if I could
pick up anything, and was switching between the bands,
tuning around. When I switched to the 5.8-11Mhz band position,
reception seemed very lively, and I realized I was listening to
broadcast band signals ....

Sure enough, firing up the RF signal generator, I could align the
1.4Mhz and 600kHz positions, using the broadcast band trimmers, with
the bandswitch at 5.8-11MHz.

After sending an email to Rodger about this amazing discovery,
I went to bed to sleep on it.

Now it seems to me my problem is very simple. When I replaced the
bandswitch rod I must have got it 180 degrees the wrong way ...
the plate that fixes it in position on the rear apron must just need
twisting through 180 degrees.

I will try this fix tonight, when I get home.

Julian (feeling a bit stupid)

Mike Everette wrote:
> Julian,
> 
> I think Al's advice is very good.  Maybe something
> miswired; perhaps a bypass cap that ended up connected
> to something other than what it was supposed to
> bypass.
> 
> But here's another possibility:  bad ground
> connection.  I saw this a couple of weeks ago with an
> HA-1 TO Keyer.  One of the tubes would not light; yet
> there appeared to be filament voltage on the socket. 
> Indeed there was; but, the ground connection to the
> filament of that tube was made through a terminal
> strip attached to the chassis with a rivet.  The rivet
> itself, or the rivet hole, or both, had corrosion.  I
> was able to clean it out with penetrating oil, then
> washed the oil out with aerosol equipment degreaser. 
> It worked; but in this non-critical circuit, I
> provided insurance by routing a wire from another
> ground point to that terminal.
> 
> 73
> 
> Mike
> WA4DLF
> 
> 
> 
> 
>  
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