[Hallicrafters] SX-71 Restoration update

[Larry Kirkland]

I just finished (?) an SX-71 here, also.  The dial cord was correct on 
it, but I need to do some more work with the 455 Kc alignment.  The 
crystal filter is not acting as it should.  I suspect the crystal has 
shifted frequency somewhat and the target freq is not 455 any more. 

I'm pleasantly surprised with how sensitive and stable it is.   Like 
Gary, I replaced all the fixed capacitors, except the micas, and 90% of 
the resistors. 

One thing that I noticed on this model, if you turn the radio upside 
down while it is out of the cabinet, one of the resting points is the 
the tuning slug of an IF transformer.  The previous owner evidently had 
not noticed this, and he really did a "number" on the poor transformer.  
I had to straighten the can and find a replacement ferrite core. 

I could have gotten by with the original electrolytic capacitor as it 
seemed to reform OK,  but I "restuffed" it anyway for piece of mind.

Now, I am going to re-read the alignment instructions for the crystal 
filter for the 20th time and see if it makes any more sense.

Larry W4LK



GBrown wrote:

>Well, only have weekends to work on restoration projects. I think you all
>know how that is. I have put all the good tested Hallicrafters logoed tubes
>in a box for safe keeping. I replaced them all with nos tubes. ALL
>capacitors and 90% of the resistors were replaced. Replaced the line cord
>with a three wire and also installed a primary line fuse on the AC. Done the
>bypass AC line bypass thing with two nos 1.6KV caps. I turned it on and
>after about 20 seconds, sound from the external speaker. Not knowing where I
>was on the dial, just tuned around on different bands and found some cw.
>Pitch works great and audio sounds good. No hints of smoke in the air. I
>turned on the signal generator and freq.counter to allow 1/2 hour warm up
>time. Grabbed the alignment instructions and was I in for a surprise. No,
>nothing was dead on freq. Matter of fact, everything was just the opposite
>of where it should be. 75 meters was way down on the left side of the scale.
>Now, this was a head scratchier. Hmmmmm, did they make SX-71's with reverse
>dials. Probably not, must be something else wrong. Well, you probably
>guessed it. Both the main tune and bandspread dial cords were strung the
>wrong way. YES, that's right, couldn't believe it. I removed all the dial
>cord and installed new cord, the right way, turned it on and alignment took
>about 1 hour to complete. Everything fell into place. Didn't even go into
>the house to have supper. Stayed in the shop till 10:00 PM just listening to
>this piece of history fill the room with AM, SSB and CW. Now, it will be
>complete when I get the cabinet and front panel back from my friends custom
>paint shop. Only problem is a lazy S-meter. I replaced the adjust pot,
>which, by the way, had a dead spot. That brought the meter back to life but
>its a bit stingy.
>Next project, just arrived, SX-62.
>Regards,
>Gary...WZ1M
>
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