First check all the obvious stuff like did you install the cap backwards, corrosion from the old battery, lifted traces...

The post a close up pic of the front and back of the board where you worked on it.

Try reseating the ROMs in their sockets. If this brings the game back, you need to replace those sockets!

It's an old board, things will fail from time to time.

But because you just worked on it, it is probably something like a connector or socket.

There is some corrosion which compromises IC sockets. The fumes get up inside them more so than damaging other components. Plus those are single wipe style.

If your roms work in a different MPU, but only give you a flicker in your MPU that used to boot. That would mean you either 95% chance of having a ROM socket error 5% chance of other errors like chip select.

Just replace all the old, crappy sockets with SIPS:

http://www.taydaelectronics.com/connectors-sockets/sockets/sip-sockets/30-pin-dip-sip-ic-sockets-adaptor-solder-type.html

The other thing you could try is booting your MPU on the bench or in your friends game. Just plug in j4 and see if it flashes up.

Sockets crap out all the time.

Just the heat from the game running will expand them and crash the CPU.

Here is a Bally MPU that I just bulletproofed for a customer for that very reason (your old Stern is the same system).

http://pinside.com/pinball/forum/topic/vids-guide-quick-bally-driver-board-repair-bulletproofing/page/2

Do you have a Solder Sucker?

sh817b.jpg

I guess I'm asking what your skill level is.

I can salvage an entire IC out in one piece with hot air, but your 40 year old Stern board is not the place to practice on.

Usually the plastic frame on an IC socket can be lifted up, leaving just the contacts behind.

Some examples here:

http://pinside.com/pinball/forum/topic/vids-guide-to-bulletproofing-williams-system-6

A contact point inside one of the socket housing probably broke. It happens, even more so when corrosion fumes potentially weakened them.

I wouldnt do socket replacement on a bally MPU unless you are well practiced. Traces go between the rom pads. Without the right equipment and practice, it can get ugly. Also if you choose to do socket replacement. Change the jumpers so you only have to use U2 and U6. That way only 2 sockets and 2 eproms need replaced.

You can use your DMM on beep test to go between the sockets pins and test continuity if you want to narrow down to a specific socket being bad. If you find u1 or u5 is the bad socket. Rejumper your MPU to use only u2 and u6 and you may not have to replace sockets.

This is where something like the FIX-IT by TwoBits.com comes in handy: http://www.twobits.com/fixit/

It has several jumpers/shunts on the board and allows you to easily switch over to the FIX-IT's RAM, game eproms or RESET circuitry without removing any of the other chips. The price is high enough that if you only have one of these games you're fixing on the cheap then it's likely not an option, but if you're fixing a lot of early Bally or Stern machines it pays for itself quick in time savings and is a great tool to have around when troubleshooting boards. It'd help identify pretty quickly if the eprom or 5101 sockets are having issues, though as others have suggested there you can do this by checking continuity, etc.