[Hallicrafters] More on my SX-115 / crystal issue / Also, need decorative aluminum knob insert

[Paul]

Got the SX-115 cleaned up and have started getting it operational. Started with the original tubes as received, just to get a benchmark. Very weak reception, although it could hear some strong stations. As suspected, the 10 meter (band 10-1= 28.0mc thru 28.5mc) band switch position is really receiving on 27.0mc thru 27.5mc due to the swapped 33.505mc crystal. 
   
  So: does anyone have a 34.505mc crystal for an SX-115?
   
  Since the radio seemed to be working, I started with a ground up alignment on the 50.75kc if.    WOW, was this thing out a alignment. No wonder it was pretty deaf. Each coil needed almost a dozen turns to peak the 50.75kc if. Right away things started coming alive.
   
  Same held true on every stage; each coil needed multiple turns (as in a half dozen or more), in order to obtain a peak.
   
  By the time I finished, the radio was really alive! I can't imagine how these coils got so far out of alignment. Even component aging and replacement usually only involves a turn or two at most to peak things up. But to have EVERY coil in EVERY stage so far out of whack, I can only think that the individual who tried to put it on 11 meters was also the one who tried to do the last alignment and got it so far out of whack they just gave the receiver up as a lost cause and dumped it.
   
  As it stands right now, I could leave the receiver just as it is and I'd be pretty happy, it receives just as well as any other receiver in the shack, including my 75A-4 and SX-101A (and I think the SX-101A can give the 75A-4 a run for it's money!). The only operational difficulty is that the audio output level seems to be a bit low.
   
  Continuing on, after alignment I figured I'd go thru and check the tubes. What I found was almost half were well below the published spec, at least on the tube tester. Yes, I know a tube tester isn't the answer to everything, it's more important to see how a tube works in the actual circuit. But I do use a tube tester to determine if I should bother trying to swap a tube out, just to see if it can be improved on. If a tube is within spec, I leave it alone. If it is below spec, I try a different one to see if any improvement can be gained. In this case, in addition to quite a few tubes being below spec, I found the VFO tube is quite gassy, and the audio amp tube, a 12AX7, has been replaced with a 12AT7. Even though the base of the tubes is the same, I don't believe the 12AT7 is an acceptable/recommended swap for a 12AX7. Inter-electrode capacitance is a bit off but the gain and plate resistance are considerably different. Checked the other tubes to make sure something
 didn't get swapped, there should be two 12AT7's and one 12AX7 used in the radio. There are three 12AT7's and no 12AX7's. I need to dig out a 12AX7 if I can find one and plug that in, see if it helps the audio, and find replacements for the other weak tubes to see if any improvement can be made there.
   
  Ok, now on to the cosmetics. Basic cleaning is done, there is still some chassis corrosion to attend to but at least it is beginning to clean up. Exterior is cleaning very nice, really looking good now. Only major cosmetic point is that the selectivity knob is missing its aluminum insert. This is an aluminum circle and appears to be about .685" in diameter. Does anyone have a spare selectivity knob for an SX-115, or an aluminum insert. Seems like I read about someone making those inserts at one point, but I can't find the reference. Anybody have a pointer to someone making these inserts?
   
  73, Paul* W2EC
   
  *(Used to be Ray but the use of on-line callbooks for logging has everyone calling me Paul at the start of every QSO, so I figure why fight it-----------)