[Coco] (Marginally Topical) TRS-80 Model I Troubleshooting

[Joel Ewy]

So I was given a TRS-80 Model I system on Friday.  It includes the 
TRS-80, an Expansion unit, a monitor, a very, very strange "screen 
printer", a pair of floppy drives, a broken but physically very nice 
CTR-80, a bunch of of programs on cassette (including a boxed Avalon 
Hill Planet Miners game), and a box labeled "TRS-80 floppy disks" that 
appear from the labels on the individual disks themselves to actually be 
Apple 2 disks, though I don't yet know what is on them.

The computer powers on.  The monitor works but has an extremely touchy 
vertical hold.  But if I power it up with the expansion unit switched on 
I get garbage on the screen.

Next time I have the time to clear the space to set it up and play with 
it, I'll try cleaning the card edge contacts between the TRS-80 and the 
expansion unit, as I gather this is a common failure.  But if that 
doesn't work, is there any other wisdom about likely problems with the 
Expansion unit?  Reseat socketed chips?  Check for bad caps?

What about the vertical hold on the monitor?  I'm not afraid of a 
soldering iron, can read a schematic, know what not to touch inside a 
TV, and where to keep my other hand, but don't have a good enough grasp 
of CRT circuits to really know where to find the V. hold parts or know 
what to suspect.  (I do have an ancient copy of TAB's "101 TV Troubles 
and How to Fix Them" or some such.  But it predates even the TRS-80 
monitor by a few years.)

Thoughts?  Suggestions?

JCE