[Hallicrafters] SX-101 mark III Question

[Carl]

The only change I would make is to improve the audio response ONLY  IF 
you like the sound of a phasing SSB transmitter or use it on AM.

Increase the value of the coupling cap ( C-97) from V-8 to .01 and 
change C-100 to 50 uF.
Disable the tone control  S-3A, or juggle values.

The radio is also pretty deaf on 10M but thats not much of an issue at 
this part of the cycle. A 6GM6 RF amp is a fairly simple mod.

I dont know why the AVC line bypass caps are only .005 uF as .01 or .02 
would be the more common value. Just something to look at if there are 
AVC related problems.

Its a decent radio but not exactly high on collector lists. Easily 
reversible mods wont hurt the value.

The first one I modified was in 1965 for K1SLZ, a fellow DXer in the 
same town. When I had a Drake 2B he heard better. When I got rid of that 
dog and picked up a 75A4 that I did several mods to I was working DX on 
10/15M that he sometimes couldnt even hear. We both had TH6 tribanders 
at 70'. I took his 101 into National one Saturday and gave it a complete 
alignment plus a few new tubes. It helped a little but still not up to 
the 75A4. A few weeks later it went back to National for front end mods 
and alignment. Larry was very happy!

Carl
KM1H


----- Original Message ----- 
From: "rbethman" <rbethman at comcast.net>
To: <hallicrafters at mailman.qth.net>
Cc: "Gary" <xfrmrs at roadrunner.com>
Sent: Monday, October 13, 2008 4:57 PM
Subject: Re: [Hallicrafters] SX-101 mark III Question


> Gary,
>
> I've had three different SX-101s over my 28 years of being licensed.
>
> I have YET to see *ANY* mods for them, NOR have I found a need for 
> any.
>
> This one I have now is the Mark III.  I got it about 8 years or so 
> ago.  a couple of owners back had added a homebrewed oscillator mod 
> for MARS use.
>
> I removed it.  It improved the radio by being ORIGINAL.  It was a 
> "hack job" mod.
>
> Yep!  Anyone whom has fiddled with bypass caps has "bit the bullet"! 
> We learn VERY quickly.
>
> Enjoy the "Old Girl", she'll serve you well.
>
> I'm ALSO posting to the list for purposes of the archives.
>
> You're welcome!
>
> Bob - N0DGN
>
> Gary wrote:
>> Hi Bob:
>>     I learned my lesson, WELL, on my first SP-600 with those pesky 
>> caps in the can. Your right, DONT SUB VALUES. As for this receiver, 
>> it is beautiful on the outside. Came with original manual and xtal 
>> calibrator. That 390 ohm resistor on the cathode of the 6K6 was up 
>> around 1500 ohms. I decided that everything in the audio section will 
>> be changed to save the output transformer. Better safe than sorry.
>> I do have an SX-101A but like this for the 160 meter band.
>> Take care and thanks again.
>> Regards,
>> Gary...WZ1M
>> ----- Original Message ----- 
>> From: "rbethman" <rbethman at comcast.net>
>> To: <hallicrafters at mailman.qth.net>
>> Cc: "Gary" <xfrmrs at roadrunner.com>
>> Sent: Monday, October 13, 2008 4:38 PM
>> Subject: Re: [Hallicrafters] SX-101 mark III Question
>>
>>
>> Gary,
>>
>> My suggestion is to NOT modify this fine piece of history.
>>
>> Once the offending caps and resistors are replaced, check alignment.
>>
>> Be careful with bypass caps in the IFs, they were pretty good on 
>> their
>> values!  Test those for THAT purpose to see WHAT the values are/were.
>> They can REALLY ruin your day if you aren't careful.
>>
>> However, I've read your posts for years!  You already know that.
>>
>> Just another happy SX-101 Mk-III owner!
>>
>> Bob - N0DGN
>>
>> Gary wrote:
>>
>>> I acquired a real nice SX-101 mark III this weekend. Cosmetics are a 
>>> 9 on
>>> the 10 scale but every single bumblebee cap is split, open or 
>>> shorted. I am
>>> doing a COMPLETE recap of this unit and also a resistor check. All 
>>> tubes
>>> will be nos. My question is, anyone have any or is there a website 
>>> that
>>> offers update mods for this fine piece of Hallicrafters history.
>>> Any replies will be appreciated.
>>> Regards,
>>> Gary...WZ1M
>>>
>>> ______________________________________________________________
>>>
>>>
>>>
>>
>>
>
> -- 
> Bob - NØDGN
>
> ______________________________________________________________
>