Hola Amigo's...

Biz Wichy here ( WDØHCO )

Hi Bill and Thermo

He's talking about the VFO in the RX section and to answer your question
Thermo - NO - that's not normal. I have 3 HW-16's and none have ever done
that.

So lets fix her...

First step is to switch V3 6EA8 with the Het Mixer V2 6EA8 and see if the
problem goes away. There's one chance in a million the tube is the
problem... if that's it then you really should be playing the lottery!!!

Second step - try swapping the 6EW6 V4 IF AMP with 6EW6 V1 RF AMP and see if
the problem goes away. This one stage away from VFO/MIX but it's worth tryin
cause it only takes a second and well who knows...

Third Step - possible cold solder joint. Give a good going over all the
joints in the that part of the circuit board. Pay particular attention to
wire "X" that connects L7. Make sure it's as short as can be and no other
wires come near it. Make sure the copper island on the board where it lands
is clean ( i.e No Rosen crap ).

Fourth Step - check all the entrances and exits of the VFO circuit. In this
case there is only two. Check R33 47K 1W resistor to see if its within 20%
of the 47K value. Just left up one leg and check with a VOM. This little guy
connects the +310 VDC bus and drops it to +95 to the plate of the triode
section of the VFO 6EA6. Hook the resistor back up and check the +95 voltage
with a ANALOG VOM. Tune in a strong signal and see if it dips as you rock
the tuning knob. Next - lets check C56 cap which goes into the cathode of
the VFO MIX. If you have a cap checker - fine and dandy - if not remove C56
and solder 2 2" 20 gauge vinyl coated wires and twist them together loosly
three times. That should be near 680 Puff. Turn on the set and see if the
problem went away. If not - put C56 back in place.

At this point - we can conclude that VFO might not be the problem. A likely
suspect could be the BFO Circuit - V5B which uses a 12AX7. since the '16
only has one 12AX7 you can't sub unless you have a spare 12AX7 - then try
it.

The fixed freq BFO is directly mixed with the IF sig at T3. R51, C72 and C77
could be troublemakers. The best way to check it is with a FREQ Counter. If
you don't have one - use a good shortwave rcvr. Attach a wire antenna and
bring it near T3 and tune it to the BFO freq on 3396.4 KC. Turn on the
Shortwave Rcvr's BFO and get a good whistle. Now tune the HW-16 to a strong
station and see if the HW-16's BFO shifts around.

Well that should be a good start. Please post what your results were.

Biz WDØHCO








Thermionic wrote:

Hi, recently I picked up a Heathkit HW-16 and with a little repair and
tune-up, its back on the air. Great!, but the receiver seems to have a
problem that may be by design or may be something wrong. So far I can't find
the cause if it's not a design flaw. What is happening is the VFO seems to
get pulled slightly by strong signals in the band, somewhat annoying. It may
be that there just needs to be a buffer between the VFO and the mixer (both
part of a 6EA8). I wonder if anyone else has seen this happen with their
HW-16? Thanks...............T


I suspect it might have something to do with power supply regulation, or
rather, lack thereof. The HW-16 has a tendency to chirp when using
crystals for the same reason. Using an HG-10B VFO seems to cure the
chirp issue since the VFO has an onboard regulator which in turn clamps
the B+ in the rig.
Our friend Biz Wichy has been known to add a regulator to the basic
HW-16 and that seems like a good idea.

-Bill