[Heathkit] HW-100/101 het osc output

[Glen Zook]

Check the six 10 ohm resistors that go from the cathode pins (there are 3 on each tube) of the 6146 finals to ground.  These go bad over the years (increase dramatically in value) and then the "plate" meter does not read correctly.  These resistors form the meter shunt when the meter is in the "plate" position (actually the "plate" meter reads cathode current).

Replace them with 1 watt (original value is 1/2 watt) 10 ohm resistors.  The "modern" 1 watt resistors are about the same size as the old 1/2 watt.

The vast majority of HW-10X, SB-10X, and SB-40X rigs that I work on have to have these resistors replaced.  In fact, I now routinely replace these resistors even if they are still close to the original value because I know that there is a very good chance that they will shortly increase in value.

The Collins S-Line transmitters and the KWM-2 series transceivers use a 12 ohm resistor in this same circuit and those resistors go bad on a regular basis in that equipment as well.

As for the restriction to set the voltage to no more than -2 volts:  This is to insure that the crystals actually oscillate every time you change bands.  If the voltage is set much more there is a good chance that the crystal will not "start" every time.

Glen, K9STH

Website:  http://k9sth.com


--- On Wed, 11/25/09, Dick KF4NS <kf4nsradio at verizon.net> wrote:

My HW100 is giving me some fits with the alignment for the first time in the 39 years I have used it. Usually all goes just as smooth as baby's rear. First thing I noticed is that I cannot dip the plate on 80M, close but not a dip.I decided to just start over.
 
The het osc setting is first of course. I am curious why the Heathkit specs state that it is supposed to be set between -0.5VDC and -2.0VDC. I can easily set mine between 0 and -7.4V. Why such a wide range? What if it is set for more than -2V?
 
The actual problem is low power output on all bands and after a full alignment and neutralizing the finals with a scope, I went back to square one as mentioned above. Any ideas come to mind other than swapping the finals? Guess maybe I should compare cathode and plate current but that is a pain to do.