I have a HP 8640B RF Generator with some broken nylon gears inside. This
appears to be a frequent problem. Does anyone know where to obtain spare
gears?
http://jvgavila.com/hp8640b.htm
They can be fixed. I had 2 cracked gears. Both are now repaired.
I'll post pictures when I can (or when I remember).
1. Take photographs of the gear assembly before removal so you know
how it goes back together. The meshing of the gears must correspond
to a starting point, so also record the position of the front panel
dials before disassembly. Be sure to record the position of the clear
plastic switch armatures.
2. Tear it apart and remove the cracked gears. The gear cracks
because the delrin gear shrinks onto the brass center piece. If you
just glue it together, the gap between the gear teeth on either side
of the crack will be excessive.
3. Remove the delrin gear from the brass center piece and file the
center hole in the delrin gear to enlarge its diameter. Leave a
little extra space around the brass center piece for the glue. Make
sure that the gap can be closed. Leave the filed area slightly rough
for good adhesion. You may also need to enlarge the hole around the
set screw for clearance with a small round file.
4. Glue the gear to the brass center piece with 24hr epoxy (not the 5
minute type). Clamp the gear in a vice, glue clamp, or whatever,
being very careful not to crush the gear teeth. Be sure the crack is
closed, properly aligned, and that no glue slops between the teeth.
Do it right the first time. Keep warm, and wait 24 hours for the mess
to dry before even looking at the results.
