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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.<br>
<br>
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. <br>
<br>
Chris, KL7DM<br>
<br>
<div class="moz-cite-prefix">On 3/4/2018 6:41 PM, Kenneth G. Gordon
wrote:<br>
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<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">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.</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">The HW-101 was extremely dirty, not having
been used for some time, but cleaned up well, and was
apparently very well-built.</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">The problem is that after the rig has been
on for a bit, the VFO quits. Completely.</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">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.</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">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.</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">So...has anyone else here experienced such
an issue with an HW-101 VFO, and if so, what did you
discover?</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">I'm going to remove the bad VFO sometime
next week.</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">I suspect I will find a bad solder joint in
it somewhere, but I am also suspicious of a bad component.
But which one?</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">Also, are replacement Jackson ball-drives
still available? These are a bit rough.</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt"><br>
</span></font></div>
<div align="left"><font size="2" face="Arial"><span style="
font-size:10pt">Ken W7EKB</span></font></div>
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