[Hallicrafters] SX-28 snipped wire puzzle

[Rob Copeland]

Glad to help! :)
Keep us informed of your project. The SX-28 is a challenge to rebuild, so it
is great to see someone bring one back up to snuff!

Take Care,

Rob Copeland

-----Original Message-----
From: Julian Bunn [mailto:Julian.Bunn at caltech.edu]
Sent: Friday, February 09, 2007 12:31 PM
To: Rob Copeland
Subject: Re: [Hallicrafters] SX-28 snipped wire puzzle


Hi Rob,

Yes ... I also had an email from Chuck McGregor saying the same.

I am going to reconnect it!

Thanks again,
Julian

Rob Copeland wrote:
Julian,

Looking at the schematic it appears to me that it is definitely part of the
Selectivity Circuit and that this is an accidental snip probably. I would
definitely reconnect it as the disconnection of the wire may effect
selectivity adjustment on the receiver specifically those in the IF Section.

Regards,

Rob Copeland

-----Original Message-----
From: Julian Bunn [mailto:Julian.Bunn at caltech.edu]
Sent: Friday, February 09, 2007 11:04 AM
To: Rob Copeland
Cc: hallicrafters at mailman.qth.net
Subject: Re: [Hallicrafters] SX-28 snipped wire puzzle


Hi Rob,

This is an SX-28. I need to double-check, but I haven't seen this
difference on the various schematics I have (including for the SX-28a).

Gary Brown has suggested it might be an accidental snip, during mods
or re-capping. I'm 100% sure I didn't snip it, so maybe when the PO
altered the circuit for the ANL it was done.

The crystal filter was working before I started on the set. I don't see
from the circuit why this snip would affect the crystal filter especially?

Julian



Rob Copeland wrote:

Hi Julian,

Is this a sx-28 or a sx-28a? If it is a sx-28 then they might of upgraded
the circuitry to sx-28a specs. I would compare schematics of an sx-28a to
your sx-28 to see if this is true. Otherwise, this would be a mod that is
not part of either spec. If this is the case you can google for

sx-28/sx-28a

mods and see if this is mentioned somewhere on the internet. If it was me

I

would just rebuild it to sx28a specs this is what I have done with mine

and

it is rather easy to do as the differences are subtle. Thinking about this
now makes wonder if the snipping was a mistake, because the 2nd IF can is
part of the Crystal Filter. If the Crystal Filter is not working this may

be

why.

Good Luck!

Rob



-----Original Message-----
From: hallicrafters-bounces at mailman.qth.net
[mailto:hallicrafters-bounces at mailman.qth.net]On Behalf Of Julian Bunn
Sent: Thursday, February 08, 2007 11:11 PM
To: hallicrafters at mailman.qth.net
Subject: [Hallicrafters] SX-28 snipped wire puzzle


In the process of re-capping my SX-28, I noticed that the wire between
the tap on the secondary of the
2nd IF transformer, T2, and C33/R19 has been snipped.

Can anyone offer a suggestion why this might have been done, and/or any
reason why I shouldn't
reconnect it?

Thanks!
Julian
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--
Julian Bunn,
Center for Advanced Computing Research (CACR),
California Institute of Technology,
Pasadena, California 91125, USA.
Tel: +1 626 395 6681, Cell: +1 626 375 4628
Web: pcbunn.cacr.caltech.edu/jjb.html










--
Julian Bunn,
Center for Advanced Computing Research (CACR),
California Institute of Technology,
Pasadena, California 91125, USA.
Tel: +1 626 395 6681, Cell: +1 626 375 4628
Web: pcbunn.cacr.caltech.edu/jjb.html