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Old 24th Oct 2020, 12:35 am   #30
mrrstrat's Avatar
Join Date: Jul 2020
Location: Rockford, Illinois, USA.
Posts: 135
Default Re: Hallicrafters SX-25 Rebuild: New Mains Transformer Questions.

I think I figured out the alignment - after following the instructions 3 or 4 times in a row I was able to complete the alignment (by ear using speaker tone). What I found is when I did the first part of the procedure, the part that a 5000Hz tone is used I noticed the different the SG had to tune to across the zero beat (to get a 5000Hz tone) was not what I thought it was.

I started alignment at 455.06 and after the 5000Hz tone portion of the alignment procedure I noticed this difference to be a SG shift to 456.19Khz (difference of 1.13). Then the bands aligned well.

When I went with my measurement of 453.06Khz for the crystal as I measured it and used that as my IF frequency it was a total disaster. The low rumbling (motor boating) I heard before was evidently a major difference in working IF and my crystal. The crystal tuning seemed to intensify the low rumbling sound and adjustment of RF gain did little to help.

When I followed the procedure the crystal tuning works remarkably well. I did tune my TXS width to cover the crystal's working range and that seemed to dramatically improve the overall performance - not too sharp and just broad enough.

Listening for a tone is less than desirable - I would always prefer a response measurement. The problem is that loudest tone seems to imply not the loudest tone, but rather the cleanest, clearest, loudest tone without distortion. I tried the loudest noise I could generate during the entire process and I can tell you that's the incorrect way.
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