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

[jeremy-ca]

How about Ray-Paul and we turn you into a Frenchie Canadian?

Keep notes on that SX-115 overhaul, I may need some when I get started on 
mine

Carl
KM1H


----- Original Message ----- 
From: "Paul" <w2ec at bmjsports.com>
To: <hallicrafters at mailman.qth.net>
Sent: Thursday, October 18, 2007 8:31 PM
Subject: [Hallicrafters] More on my SX-115 / crystal issue / Also,need 
decorative aluminum knob insert


> 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-----------)
>
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