Are there any good pinball sites or forums that list machines for sale? EM machines preferred.
You said you preferred EM machines. If you collect electronic machines, be very careful of Gottlieb System 1 MPU (CPU board)
based machines. These would have been among Gottlieb's earliest electronic machines. The original System 1 board has several
design flaws that make it very fragile. Certain IC failures as a result of the board's design flaws render it effectively useless, as
replacement parts for the board aren't really available. There are complete aftermarket replacement boards, but they are not cheap.
Apparently the other boards in a System 1 machine were prone to problems as well.
I know this because several years ago I had the one of their electronic Sinbad machines, and learned the hard way it would be an
expensive fix. Mine was missing the power supply board, which led me to conclude the CPU board was likely bad.
This machine was also available in two EM versions- a lower scoring version with the "Sinbad" backglass set up for scoring tumblers,
and one named "Eye of the Tiger" with a different backglass, and scoring configuration I think. IIRC, "Eye of the Tiger" is the more
desirable of the two EM versions, as far as collectibility goes.
P.S. Original System 1 CPU boards could be found on eBay a few years back, but my impression is that failures were so pervasive that those boards
aren't worth the trouble.