[R-390] More geartrain rebuild info

[Barry]

One thing I'd like to add to all this.  When disassembling the planetary
gears, I discovered the spring-loading mechanism is different from the
standard ball-point-pen-style springs in the other gears.  These are a
single circular piece of spring steel enclosed inside the gear halves.  Each
half has a hollowed-out place to accomodate the spring.  If your geartrain
is particularly gritty, these can be great little traps for dirt.  While you
can probably get the regular flat split gears pretty clean without
disassembling them, it would take a lot of washing and blowing to get these
gears really clean without disassembling them.

As I said, the more I see in this geartrain, the more I'm convinced I need
to give my first radio the same treatment.

Barry(III) - N4BUQ