Well, I have had an EK in my mix for years, and the knocker assembly has always just been laying in the bottom waiting on my lazy butt to trouble shoot. I had a new solenoid ... an AO-26-1200 with diode and noticed Marco suggests this as a replacement for the manual specified AR-26-1200. So, I place this into the bracket and wired. I also check the transistors and did in deed find one that appeared to be open at Q3...I replaced that, and "ASSUMED" it was surely the same trans. that Kiss uses for the knocker... it all worked out in my pretty little head. So I assumed I was going to power up with a new transistor and new coil/diode... what could go wrong?

I found a transistor legend online that does not even show a knocker transistor with a "Q" number for which one it is. Now, I know all EKs have knockers,.... so I assume the information is wrong. That particular peice of info shows Q3 as "unused"

Well, it immediately popped F4 fuse in test mode when it got to the knocker. So... I commenced trouble shooting. I do indeed have +42 volts at the yellow wire at the new coil. The coil does NOT fire either. I unhooked the black wire and touched that tab to ground with a test lead as a test to see if the coil would fire .. and it just pops F4 again and does not fire.

Will this coil... AO-26-120 not work for the intended AR-2-1200?

What can I check guys? Also, can anyone who is more experienced than I tell me which transistor runs the knocker in an EK?
While I am at it... I ASSUMED the white wire with yellow spots and the black wire with yellow spots were the correct wires (as they are the only wires I see not hooked to something) Can an EK owner tell me what color wires are soldered to their knocker coil please.... just as verification.

Thanks guys. Well, I am going to change the transistor... it's open again. However, I DID have the white/yellow wire on the banded side. I am going to also measure the new coil. 10 ohms is my target.... thanks for that. I did not know what I should measure.
So, I will start again with a new transistor, measure the new coil to make sure it's not bad (and diode). I agree! It should have fired right away hooked up wrong... it did not.
Hmmm, if this does not work.... I will report back here to complain, whine and ask for help.

Thanks guys. Well, I am going to change the transistor... it's open again. However, I DID have the white/yellow wire on the banded side. I am going to also measure the new coil. 10 ohms is my target.... thanks for that. I did not know what I should measure.
So, I will start again with a new transistor, measure the new coil to make sure it's not bad (and diode). I agree! It should have fired right away hooked up wrong... it did not.
Hmmm, if this does not work.... I will report back here to complain, whine and ask for help.

Ok,resolved the issue.... Bad diode (open) on the new coil. I suppose I could have killed it...but not sure how.....but nevertheless it's fixed. Knocker is knocking for the first time in years.
Next issue... And last remaining non working part. The extra chime at position #7 on the self test does not fire, nor during game play. I can ground the tab on the transistor AND the coil and it fires fine (new coil ..and yes good diode). I test the transistor and it tests good. It just won't fire via self test or during normal operation (although by looking at the manual..I am unclear where the "extra chime" is to work.
My game does have the ultimate MPU in it... I wondered if it just had a programming flaw in that it was not programmed to include the extra chime in operation or test? I just cannot find an issue of continuity to the coil for power(42 at the coil) and I have tested the wire continuity to the driver board...it's good and it fires fine by grounding the tab of the resistor.
Could it be the pre transistor chip... With just 1 coil not firing?