[Heath] HW-101 VFO

[ChrisIwata]

 From memory of my old HW-101, the VFO was powered by an external 
reverse-biased BJT acting as a Zener diode: I'd check this before 
removing the VFO.  I think the breakdown was something like 7 volts.  
Even if it's good, replace it with a true Zener; a BJT is not meant to 
be used as a Zener for any appreciable current.

If the bug is in the VFO, it's likely the JFET.  The gate-source 
junction is suspect.  If you look at modern JFET VFO schematics, they've 
added a 1N914 here as protection.

Chris, KL7DM

On 3/4/2018 6:41 PM, Kenneth G. Gordon wrote:
> I thought I would check here to see if anyone beside myself had run 
> into this problem: I am working on a friend's HW-101 which he recently 
> bought at a garage sale for $50.00 with an HP-23 and a Heathkit speaker.
>
> The HW-101 was extremely dirty, not having been used for some time, 
> but cleaned up well, and was apparently very well-built.
>
> The problem is that after the rig has been on for a bit, the VFO 
> quits. Completely.
>
> I hooked my Tek 2467B scope to the output coax and although when cold, 
> the output is good and is a pure-looking sine wave, within about 15 
> minutes at the longest, the output amplitude begin to fall, then 
> suddenly completely disappears.
>
> I have a "spare" HW-101 VFO here which I "clip-leaded" into place, and 
> with that one in operation, the rig works exactly as it should. It 
> even appears to be properly aligned.
>
> So...has anyone else here experienced such an issue with an HW-101 
> VFO, and if so, what did you discover?
>
> I'm going to remove the bad VFO sometime next week.
>
> I suspect I will find a bad solder joint in it somewhere, but I am 
> also suspicious of a bad component. But which one?
>
> Also, are replacement Jackson ball-drives still available? These are a 
> bit rough.
>
> Ken W7EKB
>
>
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