(I apologize in advance -- I tend to get a bit wordy on a good day, and I'm not sure what details might be useful here, so I'm including what I can remember)
I'm trying to help a friend with his Volcano after it had a coil stick on (on the saucer up above the third flipper) and burn up.
While debugging that one, found the coil for the Fire Pit had also done some cooking, and both had an issue that the coil sleeve had bubbled up to the point it completely blocked the plunger from being able to pass through the coil at all. Replaced both coils, checked fuses (because I was fairly shocked one hadn't blown in the process of a coil smoking), and now I've got a bevy of other problems:
1) the fire pit coil still won't fire at all. When the ball enters, it scores, sits, scores again, etc.
2) the game launches a second ball into the shooter lane shortly after the first ball is launched and starts activating items on the playfield. When the first ball drains, another ball gets launched into the shooter lane, despite one still being there.
the good news is the saucer that was the original problem is working great 
So I've found info on pinwiki and an old webarchive of pinrepair for generic System80 troubleshooting, and I'm getting ready to start working through some of those items.. the first question I had was regarding the mention (on both pages) of testing the transistors by use of a test "wire with clips" and clipping onto a ground and then touching the coil lug or resistor tab/case to ground out and test fire the coil... pardon my ignorance, but are we talking literally just a wire with a clip on one end (so I don't have to hold it on the ground) and a bit of bare wire on the other end or a clip to touch with? Should it be fused or have a diode or anything as protection? Can this be done with a DMM, or is that just putting my meter at unnecessary risk when I can just get a simple wire?
as far as things I've already checked on this particular machine, if anyone has any other vague guesses or specific advice to throw at me (as I'm always looking to learn):
1) I checked voltage to ground from both lugs of the fire pit coil, and I'm getting 25vdc on both legs.
2) I verified the wiring to the new coil (on both replaced coils) matches what existed before I took out the burnt coils, and both match the schematic as far as having wire from fuse to coil on banded side of diode, and non-banded side of diode lug goes to transistor. I've checked continuity on both those wires, as well as confirming the transistor to ground continuity and have chased the other end back to the 24v supply in cabinet.
3) I've plainly not yet done the test jump to ground from the coil or the transistor, as I'm just now finding that info on indicated links, so that's my next step -- but since the machine is an hour away, I'm trying to line up about 2-3 levels of things to check, based on what I see, so I can hopefully isolate and solve it in as few trips as I can manage.
as far as the extra ball kicking into shooting lane, I've checked switches and continuity from the trough switches to other elements in each row/column and confirmed other elements are working in each column/row as well.
I'm thinking my current plan of attack is to try firing the fire pit coil via the solenoid test mode (which I hadn't figured out yet on my last trip), and if that doesn't work using the test-wire method to jump to ground on each of the coil and the transistor... if both coil and transistor test as expected, am I pretty well isolated at that point to a problem in the driver board? (which I suspect is likely, considering it's plainly had issues in the past from it's condition -- one of the 2N3055 transistors has previously burned up the board, and is currently sitting suspended from the board by the wires attaching it back to the burned out traces).
as for the extra ball kicking out, I was originally thinking some sort of issue with the trough switches not recognizing a ball had already been ejected -- but I haven't found any continuity issues between switches and their respective row/column mates... other than checking the connection for the rows/columns back to the board, is there anything else to be suspect of on those?
Any other tips or suggestions you can make for a (very long-winded) newbie trying not to screw up to bad? 
Thanks in advance,
Berz
