Let's get you started.
Did the displays =ever= work?
If you have 60V DC and the 8V "bias" voltage, then the large displays should work.
The BIP/credit display works from the 42V and 3V bias voltage.

If you have voltage, and have =never= seen the displays work, try "recharging" one with this procedure:
http://www.pinwiki.com/wiki/index.php?title=Gottlieb_System_80#Rejuvenating_Tired_Displays

Don't over-do-it. We are only looking for signs of life to rule in/out tired displays.

After you recharge it, disconnect the other 4 displays, connect the recharged display, then power on.
Got display now?
--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

It's not uncommon for the 6532 ICs to fail.
The most common is U4, which drives the switch matrix. It fails via HV being shorted to the switch matrix.
But, I've seen U5 fail too. Most of the time when a 6532 fails, the MPU will no longer boot, but I've seen them fail in ways that still allow the MPU to boot.

At this point, I'd socket and replace U5, which is non trivial. If you have significant PCB rehab experience, have at it. Otherwise, send it to a pro. If you are in the US, I can take care of it for you.

6532 chips can be purchased here: http://bigdaddy-enterprises.com/ although you'll have to contact him (Todd) directly as his web site for that part is still under construction. Good seller.

--
Chris Hibler - CARGPB #31
http://www.ChrisHiblerPinball.com/Contact
http://www.PinWiki.com - The Place to go for Pinball Repair Info

Check the schematics but I believe that both of those coils may be driven by under play field transistors. Todd also stocks 2N5884 transistors which are a good substitute for the OEM part. Get a few of those. 1N4004 diodes may come in handy too.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact/
http://www.PinWiki.com - The new place for pinball repair info

Let me make sure I understand completely.
The game boots, goes into attract mode, can even enter diagnostics, but you have no displays. Is that correct?

Chris

A logic probe is what you need now. Start at the 7448 outputs and work backwards.
--
Chris Hibler - CARGPB #31
http://ChrisHiblerPinball.com/contact
http://www.PinWiki.com - The new place for pinball repair info