I personally think you should at least attempt to fix it yourself. There are plenty of people on this board with expertise on that bally/stern system to help you along.
In theory the bally/stern rectifier board is a good first project. It's a very simple circuit with few components that are all still available from many suppliers. The problem though is when you actually start soldering on that beast... or more specifically desoldering. The pads for the bridges are huge and tough to get hot enough to melt the solder which doesn't exactly melt like brand new stuff in the first place. You're going to need a good iron.
With all that said I still think repairing the rectifier board is a good first project. Myself, I would rebuild it with all new bridges, heat sinks, connectors, etc... but I would still test it first and figure out what problems exist. It's not a good idea to just start installing parts without knowing what you're dealing with. You could introduce a new problem and really complicate things.
Start by checking the fuses on the rectifier board. If one is missing you could replace it but assume it was missing for a reason and might blow. I try to avoid wasting fuses by checking the bridge associated with any fuses I find blown before just installing a new one. In this case it's probably going to be easiest to do your troubleshooting at the cost of a few fuses.
Here is a method to test the rectifier board with it installed in the machine quoted from the manual I posted earlier:
On -18 and -49 power supplies (pre-Xenon), before beginning make sure your transformer and regulator board work. Attach only connector J2 (remove connector J1 and J3). J2 brings 120 volts from the power cord to the transformer and regulator board, which allows us to check the test points for proper voltages. The best place to pick up ground is at resistor R1 or R2's , lead closest to the fuses (or on rectifier board AS2518-54, on the right side of the R1 resistor). This info applies to all three generations of rectifier boards (AS2518-18, AS2518-49, AS2518-54).
* TP1 (on AS2518-18) = 5.4 volts DC +/- .8 volts (4.6 to 6.2 volts). Fuse F1, bridge BR1. Used to power the "switched illumination" (feature lamps).
* TP1 (on AS2518-49 & -54) = 6.5 volts DC (5.8 to 7.2 volts). Fuse F1, voltage regulator RP1 and RP2. Used to power the "switched illumination" (feature lamps).
* TP2 = 230 volts DC, +/- 27 volts (203 to 257 volts). Fuse F2, diodes CR1 to CR4. Used to power the score displays.
* TP3 = 12 volts DC (11 to 16 volts). Fuse F3, bridge BR2. Used to power the regulated +5 volts DC for the game's logic circuits.
* TP4 = 7.3 volts AC, +/- 1.0 volts (6.3 to 8.3 volts). Fuse F5. Used to power the general illumination.
* TP5 = 43 volts DC, +/- 5.4 volts (47.6 to 48.4 volts). Fuse F4, bridge BR3. Used to power all the coils.
If fuse F2 is blown and no high voltage at TP2, almost for certain one of the four 1N4004 diodes next to fuse F1 are shorted. Use a DMM set to the diode function and test the diodes. In one direction .4 to .6 volts should be seen, reverse the leads and null voltage should be seen. If fuse F3 is blow, suspect bridge BR2 as shorted. If fuse F5 (TP4) is blown there is a short in the general illumination circuit. If fuse F4 is blown, suspect bridge BR3 as shorted.
Quoted from this section:
http://www.pinrepair.com/bally/index1.htm#ps
In summary:
1. Remove all connectors from the rectifier board but J2
2. check voltages at test points
EDIT: You asked for parts suppliers so here are a few I use:
http://www.pinballlife.com/ - Check here first. Terry is a great asset to this hobby and his prices are great. Whatever he has that I need I get from him. Unfortunately he doesn't sell everything. Rubber kits are one example.
http://www.marcospecialties.com/index.asp - I've installed tons of their rubber kits with no real problems. Others have not had the same experience. Not always the cheapest but I've had no complaints and made many purchases.
http://www.pbresource.com/ - Good source for rubber kits. If you need Gottlieb parts this is the place to go. Lots of NOS playfields for odd Gottlieb games. Many other NOS and repro parts for other manufacturers. If you need something and can't find it at least check with Steve.
http://www.greatplainselectronics.com/ - great source for electronics components. If I have a large order of electronics components I like to buy from Ed. Again... many purchases and always satisfied.
There are many others but these are the main one's I've used.
