[Heathkit] restoring HW100

[R.J.Keller]

Well folks, time to show and tell. The restoral is just about done.
Here is what I did/found and comments:

1. Removed all tubes and cleaned the entire chassis, top and bottom
with Chemtronics Electro-Wash PN. Many stubborn spots required extra
cleaning with a bristle brush (we used to call them paste brushes)
using Reagent Alcohol (mixture of denatured and isopropyl alcohol).

2. Made mod's from the Improving/Optimizing files available on the
net. Most involved component and component value changes in the
S-meter, AVC, IF and audio circuits. Changed mike jack to .210
Swithccraft to match the Drake (this is better than using a 1/4 in.
phone jack since it is impossible to insert headphones into the mike
jack by mistake)

3. Cleaned all pots, switches, tube sockets and jacks with Deoxit D5.
Also applied Deoxit to tube pins. No drowning, just light application
is needed.

4. Modified the coil cover by moving the rear flap from over the
underside tank enclosure to in front of it. This required soldering a
nut to the inside of the flap since the screw used to thread into the
tank enclosure. Then I had to re-drill the holes for the three side
screws. Also the spring clips no longer lined up with the shields so
they were removed and replaced with homemade spring clips attached to
the shields. I applied Penatrox to all the contact surfaces of cover
(top, side and rear) to improve grounding.

5. Added 80mm fan to rear of PA cage (cut out the strips of metal on
rear panel behind the fan) and built a 12VDC P/S on a 1/1 perfboard
using a 1000mfd 35V electrolytic, 1N514 diode rectifier and a 47ohm 1W
dropping resistor. The resistor isn't needed but the filament voltage
was over 14VAC and after the diode it was over 16VDC. Now the fan
supply is 12.6VDC and as an added result, the filament voltage is
12.7VAC with the fan load on there.

Now comes the real fun. I gave it the smoke test. Yep, smoke. I
created my own nightmare. One of the  300VDC switch tabs was touching
the coil cover. Then when I powered up again the rig went into
transmit. The mike jack keying lead was touching the front panel after
tightening the jack.

Try again. This time the S-meter was full peg and ungodly static
coming from the speaker.
Found 12 cold solder joints, mostly wires attached to the trace side
of the circuit boards. Heated/re-soldered 80pct of connections on 4
circuit boards.Guess I brushed too hard but I prefer the positive
spin; these were things that needed fixing.  I attribute the numerous
cold solder joints to bad Heathkit solder as well as my excessive use
of flux when I built the radio. (and I thought I was the worlds best
solderer, darn)

The last big problem. When I tried to set the BIAS it pegged the
meter. I fought this bugger for over a week; tracing wiring,
resistance checks, voltage checks, more visual inspection. The voltage
checks were totally baffling. One thing pointed in one direction, then
back the same way and round and round. Found it totally by
coincidence. I was doing voltage checks in the PA and took the cage
cover off to test the plate voltage; as soon as I touched the lead to
V8's plate cap the needle dropped back. Strange, I had already tried
other 6146's already. The actual cause was loose contact in the tube
socket. Easy fix.

Did a complete and meticulous alignment. The receiver is really hot,
the audio noise level is so low I had to see if the volume level was
turned up. Re-soldering is the reason, I am sure. Also tightening all
screws everywhere. The raspy nature of the receive audio has been
improved with the change of C119 to .001mfd. Still, Heath did a poor
job designing the audio stage. Wish there was a way to make it sound
like the Drake or Collins receivers.

One last suggestion to anyone having a problem with slow receive
recovery after a long transmission, add a diode to the PA screen
supply. It fixed mine.
Ahhhhh, the joy of having my HW100 back on the air. It feels so good I
think I need a smoke. (little humor there)

73 and Heathkit forever, Dick KF4NS