2025.08.17 second HAM-IV rebuild
2025.08.17 second HAM-IV rebuild:
I periodically see CDE control boxes at hamfests selling "solo" (without rotor) and when they're reasonable,
I pick them up because people DO sometimes need one. They usually need a new start capacitor, a meter lamp,
and occasionally a new power switch.
Rotors on the other hand, are quite rare to see by themselves at a hamfest. And when they're being sold with
their control box, the prices are almost always outrageously high. So I count myself very fortunate to have
ran into a Ham-IV rotor for sale solo this summer at the Cedar Rapids hamfest. The buyer kind of gave me a
bit of a "good luck fixing it!" vibe when I bought it cheap, but that's okay, I think it's within my ability
to repair if it has issues. Maybe a lightning strike took out the position resistor (parts are available, not
too expensive), or the bearings are rusted (I have almost a full kit of new bearings) but the big one will be
if it has brake teeth broken on the lower housing, I don't know what that will cost to replace if it's bad.
Doug (K0DV)'s rotor recently stopped working and he's been trying to troubleshoot it, so that gave me a bit
of motivation to test out this new find, as well as dig a control box out of the basement and see how the two
untested units would perform. Right now all it does is make a really loud brake release sound from up on the
tower, but it won't turn. He's done basic tests on the box (like checking the start cap) but at this point he
really needs spares to swap around to see if the control box, wiring, or rotor is the problem.
My initial impression was the rotor has surprisingly little rust on it, except for the control cable lugs
of course which are always severely rusted. I've got them stewing in some Rust Evaporator and we'll see how
well that works on them. (my first time using the stuff) It came with a lower mast bracket, which is a bit
unusual, as well as the top mast plate WITH u-bolts. What surprised me the most though was the mast pinning
bolt was NOT rusted frozen to the mast plate... I was able to remove it by hand. (this never happens)
Even the bottom pipe bracket bolts were rust-free. it's almost surreal to see...
So I spent a few hours fabbing up new quick connectors (automotive 8 pin high current, "harsh environment" grade)
and to my great surprise, both the rotor and control box seem to be more-or-less fully operational. The control
box's start capacitor only tests at 97uF, but that's still a passing grade. It even has the original power switch
(which is working fine)
The rotor is in a bit worse shape. The position indicator gets pretty noisy for about 90 degrees around West,
and around that same area it seems to bog down with a noticeable change in sound. When I was filming it in
operation, it actually stalled out and I had to restart it. (first time I'd seen it stall) It did restart just
fine though. Probably needs a good greasing of both the gears and the bearings, or might have a jammed bearing.
The position resistor is working but the noise could indicate minor lightning damage, but I'm betting it just
needs hosing down with some tuner wash to clean the wiper and resistor windings. There are no signs of sealant
along the seam between the two halves of the housing, which is a bit concerning. It may just have a slug of
rusted bearings all around the track inside?
I'd rather not open it up if I don't have to though, since these rotors don't have a gasket at the seam and
you have to re-seal them with something like RTV sealant whenever you open them. (after cleaning out the old
sealant) With the high overhead for taking it apart, you want to take that opportunity to perform all the
regular maintenance you can so it'll go another 15-20 years before it needs opening again. I have almost a
full set of fresh bearings and half a can of grease, and my tube of RTV might still be fresh, so maybe I'll
give it a go a little later if I'm feeling ambitious.
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testing operation.MOV (248 MB)
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