Symptom:  No display, spot killer on, steady series of 8 beeps, long, low tone, repeated over and over, start LED off, will not respond to coin switches.

1.    Located bad IC at N6 - this cured beeping problem.  Board now played blind, all sounds correct, response to control panel buttons ok per sounds.  IC located using HP10529 logic comparator - priceless tool for quick in circuit IC testing (no, sorry, the 2 I have are not for sale :)  They do crop up on eBay now and then for ~ $50.

2.    Scoped X and Y outputs - both dead.  Found bad cap (lead broken) at C59.  Replaced with .047@50VDC.  Board now has good X output.

3.    Located, by replacement, defective IC at E10 (LF13201) and defective op amp at D10 (TL082).  Board now works, game plays, shows "L" error in self test.

4.    Replaced 2 sockets on math box board to eliminate "L" error (outer 2 2901 sockets).

NOTE:  I got VERY confused with the X and Y output repair.  If you scope pin 18 of the DAC on a working board you will see only a very low amplitude waveform, almost like grass with a series of twigs sticking up.  This appears to be the norm.  On the Y side, where I had a good DAC and a bad opamp and switch, the output of pin 18 of the DAC appeard to be a fairly normal low amplitude vector signal.  I am not sure what this is all about, and will check it again by re-installing the defective ICs at E and D 10.