[Hallicrafters] SX-100 Mark 1A

[jeremy-ca]

If you could post that info somewhere it would be appreciated.

Carl
KM1H


----- Original Message ----- 
From: "Jim Liles" <james.liles at comcast.net>
To: <hallicrafters at mailman.qth.net>
Sent: Tuesday, November 27, 2007 10:15 AM
Subject: [Hallicrafters] SX-100 Mark 1A


> Hi Roy:
> Your friend has acquired a fine radio.  Regarding the 50KC sub-chassis, 
> there are no paper caps on that sub-chassis and you can measure all 
> resistance values from the tube and crystal sockets --- no particular 
> reason to remove it unless it is failing.  A recommendation for the Mark 
> 1A is to bring it to Mark 2A level.  There are only 6 changes as I recall 
> which make the radio sound and operate on sideband like a product detector 
> has been installed.  You can run the RF gain full out and not have to deal 
> with distortion.  A couple of the alterations are, the BFO is tapped on 
> the plate side rather than the grid side of the BFO oscillator.  Next, 
> they changed the AM/CW switch from a single pole to double pole in order 
> to implement slow AGC on CW/SSB which enables the RF to be left on 10 for 
> SSB.  Next, This is a good one, align the 50KC IF system at 50.75KC not 
> 50.50KC.  This accomplishes two things; It reduces the presence of the 
> unwanted sideband and reduces the reverse feedthru of the BFO oscillator 
> from the detector/V7 to T6 to T5 to the AVC detector --- this reduces the 
> affect the BFO has on the S-Meter.  There are a few resistor changes but 
> I'll need to review the schematics as they escape me --- too early in the 
> morning.  Kindest regards Jim K9AXN
>
> Original message:
>
>> Halli Folks,
>>
>> A friend has gotten from his uncle an SX-100 Mark 1A.  I've seen them 
>> discussed
>> on the list with high praise.
>>
>> Most likely I'll get to replace caps and do an alignment on the thing.  I 
>> will
>> want to do a good job since this is both nostalgic for my friend (he 
>> lusted
>> over them in catalogs) and from a family member who was the original 
>> owner.
>>
>> I can see from the BAMA manual that this is a fine receiver, in some ways 
>> like
>> the SX-101A.  I also see that it has a 50KC IF module that's bolted to 
>> the
>> chassis with some 10-12 leads to manage.  (I just finished an SX-88 and 
>> had to
>> remove/replace the IF module.)
>>
>> Any tips or gotcha's on this receiver?
>>
>> Roy,
>> K1LKY
>>
>> Roy Morgan
>> 13033 Downey Mill Road
>> Lovettsville VA 20180
>
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