Just turn the power on and look for smoke!
I'm kidding of course. Before turning anything on, clean everything. This is particularly important with the front panel PCB and the backplane. If you don't want to take the backplane out completely, which can be a bear, vacuum it good and then turn it over and give it a good shake. Disassemble the front panel assemble so that you can get to the front panel PCB. Look for buildup of crud and clean with some denatured alcohol. If it's really bad, pull all of the IC's and give the board an alcohol bath. The reason for this cleaning exercise is that I've found the front panel extremely sensitive, resulting in stuck address / data lines and flaky timing during examine and deposit operations.
Once all the dust bunnies have been chased out, power it up, with no boards installed, and verify you're getting +8 and +/-16 out to the backplane. Next, put back the front panel and a CPU card. Power it back up and yes, this time, look for smoke. If you have a scope, now is a good time to check each of the DC power lines for ripple. If you see anything significant, you probably have lost one of the filter caps.
Now it's time for the fun part. Press and hold the reset lever up. You should see all of the LED's go on. When you release it, all of the address LED's should go out. If I remember correctly, the data LED's will remain on. You should now be able to set the address LED's by flipping the address switches and toggling the examine switch. Test each address bit looking for ones that are either stuck high or low. You should also be able to toggle the examine-next or deposit-next switches and see the address increment by one each time. Now you can add a memory card and see if you can peek and poke data into memory. Again, look for stuck bits. This time, not only address bits but data bits. If everything is found working up to this point, you're in very good shape. If not, then it's time to pull out the schematics and get to work.
Have fun!