Fw: [Hallicrafters] Fw: SX-101A VS SX-115

[Paul Kraemer]

----- Original Message ----- 
From: "Harry Vaught, KT4AE" <kt4ae at bellsouth.net>
To: <hallicrafters at mailman.qth.net>
Sent: Tuesday, October 14, 2008 2:13 PM
Subject: Re: [Hallicrafters] Fw: SX-101A VS SX-115


> I've never had an SX-115, but I've had some SX-117's and an SX-101A.
> 
> Back in the Spring, I cured essentially all the drift in my SX-101A - 
> almost accidentally.  After a 45 minute QSO on 15 meters where I was 
> chasing the other guy up and down within about a 2 kc range I did the 
> following:
> 
> I replaced the 12BY7 oscillator with a new tube. This shifted the 
> calibration by about 20 kc.  I took the hood off the main tuning cap, 
> properly indexed the dial pointer and then re-aligned the RF coils to 
> correct the calibration.  I didn't fool with the soldered trimmers.
> 
> After this, given a few minutes warmup, it's almost as stable as an 
> SX-117 (my current one is rock solid).  As an added side benefit, dial 
> tracking is much improved.
> 
> I think it may be largely luck that determines which 12BY7 is going to 
> be a stable one.  I've had this receiver about 13 years and have 
> replaced the 12BY7 a number of times without notable change in the 
> drift.  I usually leave it plugged in so the 12BY7 is hot and the heater 
> is on.  I unplugged it a week go when we went out of town for the 
> weekend.  When I plug it back in, I'm going to check and see how long it 
> takes to become stable again.
> 
> Harry, KT4AE
> Maryville, Tennessee
> ______________________________________________________________