If you take a piece of wire with an alligator clip at each end....clip one end to the "tab" at the top of the transistor Q53 (I'm trusting you that's the correct one).

With power on to the machine, briefly touch the other end of the wire to ground. This will complete the ground circuit and the coil in question should fire (5 ohms should be fine as tested).

If the knocker coil fires, this tells you that all of the wiring, connectors, mechanical things, etc. from the point of that transistor to the coil are fine. If that's the case, I would replace the transistor and the pre-driver transistor (I assume there is one).

If the coil does not fire when you ground the tab, you've got a problem somewhere else - between that transistor and the coil itself. Wiring, connectors, bad coil, etc. Fix that first before you deal with the transistor.

This test doesn't tell you if the transistor is bad or not - it simply confirms the "flow" through the machine. But it will isolate the existence of a board problem versus a playfield or connector problem.

If you can't find the exact 2NXXXX number try the NTE cross reference:

http://www.nteinc.com/

They combined with ECG many years ago. NTE replacement parts are readily available.

You can also search these for the exact manufacturer part number :

www.jameco.com
www.mouser.com
www.newark.com

But you can still run that test with a bad transistor since it is not really "using" the transistor to do anything. It's just acting as a grounding point to test your signal flow.

Now if your trannys are blown up and not even connected to the board, of course it's probably not going to work. But in that case I'd find the appropriate pin out on the board and ground that - again, just to confirm the coil, wiring, etc. is working OK so I don't blow up a new transistor when I put it in. If you have any concerns about the coil itself, you can ground the lug directly on the coil and that should fire it also.

Again, just a small bit of insurance before you put the new transistors in.

5 ohms sounds low to me, though I don't know much about the gotlieb pins. What voltage do they drive that coil with? Is the current that it would pull with 5 ohm resistance consistent with the size of the fuse?

If it's 50v like the big wms/bally coils, that'd pull 10 amps, which would pit your transistor against your fuse in a race to see which would blow first.

Q53 should be a 2n6043 transistor q54 is an mps-u45 but you will have to get the replacement cent-u45 as the other is damn near impossible to find. I have a Star race which was the pin produced just before yours and I'm pretty sure that the driver boards are all the same for the system80 machines. Do you have a manual? If so you can look all the transistors up in it and see what all do. I will look in the repair guides and give you the possible replacements for your transistors etc.. if you just tell me what they are or where they are located.

Glad to to help but the price you stated of $45 is outrageous for a single transistor. Even one that is ultra rare/discontinued. The Ni-Wumpf board is a better choice for a quick fix.

I will see what we have at work in old stock for what you need. Or at least take them for myself before they get tossed out.

Justininia sent you an pinside e-mail. the help you need is in there

You can get a replacement driver board at pbresource.com for $84.00

Gottlieb driver boards are one of the easiest to repair.

It's the MPU of the System 1 stuff (spider chips) are tough to find....

Go to this guy for *all* your Gottlieb needs! And he has both of those transistors cheap...

http://www.greatplainselectronics.com/search.asp?pg=1&stext=2n6043&sprice=&stype=&scat=

Q54 is a mps-u45 but this chip should not be in use unless someone put in a coin counter as this was an option Gottlieb offered. Should be three transisors like this so you really shouldn't have to replace this and can rob the other two transistors to use elsewhere.

You are looking at the wrong Transistor .

Take Schusler's advice:
Go to this guy for *all* your Gottlieb needs! And he has both of those transistors cheap...
http://www.greatplainselectronics.com/search.asp?pg=1&stext=2n6043&sprice=&stype=&scat=

You also need Clays System 80 repair guide but it is taken down from his site.

I have been using Mosfets to replace blown driver transistors on system 1 driver PCBs.
More snap on the solenoids when using Mosfets.

I am doing one driver PCB with all 8 drivers replaced with Mosfets.