[Boatanchors] Need Crystal Phasing cap for HQ-129X Receiver

[Michael D. Harmon]

Hi Everybody,

I just rescued an orphan HQ-129X receiver.  Maybe I'm nuts, but I saw it 
at my local electronics emporium and it just cried out for me to take it 
home with me.  So I did.

I used a 129X back in the Sixties at my college club station.  Quite a 
few CW QSOs with that old radio - tinny crystal filter and all. Anyway, 
after I got it home, I checked
it over to get a general idea as to how much work was ahead of me. The 
thing is full of old wax-paper .02 and .05 uF caps - no problem.  The 
meter housing was all split
and resembled an old riverboat smokestack - I can fix that.  And for 
some reason, the shaft on the Crystal Phasing variable cap (C21) barely 
came through the front panel
  - maybe 1/8" - not enough to attach a knob - strange.

The front panel was awful, so I wasted no time tracking down a better 
panel.  After I got the old panel off, I started looking at the Crystal 
Phasing cap shaft.  After I opened
  up the crystal filter enclosure, I saw that the cap had been 
replaced.  Whoever had done the work had done a pretty sloppy job, and 
had stuffed a BFC-12 butterfly cap into
  the enclosure.  I know the original cap used the APC-style mounting 
posts spaced 5/8", because the enclosure has a shaft hole with slots for 
#4 screws going left and right
  for a total of 3/4".  The replacement cap has the tapped posts as 
well, but they are spaced 1-3/32" (tapped for #6 screw) plus a standard 
3/8" mounting bushing.

The person who installed the BFC-12 had to ream out the shaft hole to 
accommodate the bushing, plus drill 2 new holes to accommodate the wider 
mounting post spacing.
The cap was physically too big for the space, so he wedged a piece of 
plastic between the stator posts and the coil can behind it as an insulator.

The BFC-12 is a butterfly cap, but the original cap had to be a 
differential cap, not a butterfly.  Butterfly caps go through their 
entire range in 90 degrees of arc, but the panel
markings show a 180 degree arc marked 0 to 100.  In addition, there is a 
small arrow at the '50' position on the scale, which would correspond to 
a half-mesh condition with
both stators of a differential cap.  It wouldn't make sense with a 
butterfly cap.  A butterfly cap also wouldn't be what you'd use to 
control a phase shift condition.

The parts list and schematic give no indication as to the correct value 
for this cap.  The parts list shows a Hammarlund part number of SA-604.  
I've looked through every piece
  of data that I have on old Hammarlund caps looking for an 'SA-604' 
with no success.  I've concluded that it's a house number for a 
custom-made part, not something that
was generally available.  I've never seen an APC differential cap, but I 
know that's what thing has to be.

I may be fighting a losing battle with this receiver unless I can find a 
carcass with a capacitor that can be salvaged.

Can anyone help me out?

Thanks!
Mike Harmon. WB0LDJ
mharmon at att dot net