Flakey 28S


I have a 28S that sometimes pauses either while running or taking
keystrokes. Sometimes it's barely noticeable, sometimes a few seconds,
sometimes seemingly "indefinitely".

The ON key and ON key combinations always seem to get it going again. Of
course ON by itself is ATTN or the equivalent of 0 DOERR, but "ON and +"
or "ON and -" adjust the LCD darkness, so they work to get it going.

With the "ON and CursorLeft" repeating self-test, it sometimes pauses,
but when I get it going, it always gets to "OK-28S"; never a failure.

With the "ON and NEXT" keyboard test, sometimes the keys stop beeping
(not repeatably on any particular key or on either half of the
keyboard), and if I keep pressing a few more keys (putting keystrokes
into the key buffer) and then do "ON and +" or "ON and -", then it
responds with a long (somewhat warbly) beep and I can continue the test
and end up with "OK-28S".

No apparent external damage and all of the keys feel ok, none mushy or
anything. I've put in tested new batteries and of course cleared the
memory, but haven't attempted any disassembly.

This has a Version 2BB ROM (as far as I know, the only version used in
the 28S).

Has anyone experienced anything like this or have any ideas on what
might be causing this or how to repair it?


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