I have a Heathkit SB-230 amp (it's the fanless one that uses an 8873).
It has been in storage for 15 years (inside the house living space,
heated and air conditioned). I just got it out, and found that the
meter pointer was stuck at zero. I disassembled the meter and found
something very strange. The moving coil is there, and in the center is
what I assume is (was) a permanent magnet of some type. This magnet
has, while in storage, decided to partially or completely disintegrate
into tiny shards of magnetic material. It has grown outward to
partially surround the coil and, I assume, the pivot, which may be why
the coil and pointer won't move.
I haven't touched anything yet, except to disassemble and photograph it.
You can see a photo at http://www.radiophile.com/meter1.jpg (80 kB). I
don't know what is underneath that outer layer of loose magnet bits. I
plan to try to blow out the crud with compressed air. Will I find a
solid piece of magnet, or has the whole thing disintegrated? If there's
a piece of magnet, I assume it won't have its original strength, and the
meter won't have its correct full-scale current. I'm pretty much
resigned to the fact that the meter is trashed.
Anyone got any advice or comments? If I can't fix this one, I wonder if
I can fit another 1-mA movement into this frame somehow? Or, anyone got
a spare SB-230 meter or a cheap junker '230?
73, W1JA
John Pelham
E-mail john@radiophile.com
Web site http://www.radiophile.com
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