[Heathkit] Problems with HW-101 - possible fix

[Kenneth G. Gordon]

On 18 Dec 2020 at 5:43, jack m wrote:

> 
> Ken,
> 
> Review the manual again with respect to the wafer notches - They are all 
> supposed to be in the same direction except for the heterodyne board - it is 180 
> out.

Yes, thank you, I discovered that. Also, I was wrong: all switch boards are installed correctly.

However, there is still something not quite right with the heterodyne board. According to the 
marking on the switch-board, that wafer is supposed to have a yellow mark on it, as does the 
crystal switch-board, but this one has an orange mark on it, and it is not faded-yellow either.

BTW, and just FYI, I am 78, and have been doing this sort of thing for many years. I worked 
as the Electronic Instrument Specialist, Sr. at the University of Idaho for over 30 years. I also 
have a pretty complete shop.

> It sounds like you have been tuning on parasitics all along

Not to me. I am quite familiar with what are or are not parasitics. I recently took care of 
parasitics in an old military version of a Collins 30L-1.

This issue looks to me as though there is something physically wrong with the driver grid and 
plate coils or their wiring.

> - these do strange 
> things, and I have never seen one specific symptom repeat itself on a different 
> rig exactly the same way.  A way to test for the parasitics is to pull V6, and see if 
> it stays at power out.  If it does stay, all the drive energy is initiating in V7  There 
> is a 50-50 chance the drive control has any impact on the output level with the 
> parasitic present.  Be sure to have the tube shields on V6 and V7, and the coil 
> cover in place.  Verify for a good ground on the tube socket for V7 shield - bend 
> the tab, and scrape the shield if needed.  Substitute a known good 6CL6 into V7 
> to see what changes.  Again, monitor the frequency you hope to be transmitting 
> on.

According to my frequency counter, the output is exactly what it should be.

> With everything all lined up, I'll wager that you get good coil peaks on each 
> band.  Just be sure to preset the preselector to 12 o'clock for 80-40-20, 2 o'clock 
> for 15 and 2:30 o' clock for 10 on the 29.0 range.  Make sure the O-ring belt are 
> pliable and tight, or you may never be able to sync the variable capacitors.  Go 
> through the sequence twice - with the last time at about 1/4 - 1/3 power to get 
> nice clean peaks on transmit for the driver grid and plate coils.

...as I have done with other SB/HW rigs for years, thanks.

> If you have a frequency counter, probe V6-1 to see the actual crystal frequency 
> you are working with for each band.  Each one should be close to xx.395 or 
> xx.895.  If these are close, then check your cal signal to see how far off the LMO 
> dial "0" point is.  You can make minimal shifts using the het osc coils, but do not 
> go much above -2.0 volts for any given coil.  To make a convenient test point, I 
> usually insert a #3-42x3/4" round head screw from the bottom side of the board 
> into the test point hole, solder it to the land and this provides a robust point for an 
> alligator clip topside when compared to the bare wire originally placed there.

Thank you, Jack. You're a good fellow.

At this point, I am going to remove the driver grid and plate switch boards and go over them 
carefully. I suspect that the original builder made an error there somewhere.

Ken W7EKB