Just got my first System 11 and am coming from an EM, so I'm drinking from the firehose. When I got the game there were two obvious issues. One was a portion of the backbox lighting was out (I haven't addressed this). The second was the right top jet did not work. The coil controlling that jet was cooked. Coil sleeve melted into it. So, I replaced the coil (interestingly, there was a replacement coil sitting in the box, so I guess the previous owner had tried to replace it but gave up). The other issue was a transistor (Q73) controlling the coil was toast, so I replaced it as well. Now, when I run the diagnostics, the jet works fine. However, when I run the A/C tests, the C side has an issue and displays err. I notice that for every C-side test the jet fires and holds. When I manually advance to the next test (A-side) the coil releases, hit advance to the next C-side test and the coil locks, and so on. Based on other threads, other sites and product documentation, I suspected an issue on the Aux power board. Transistors seem fine; however, there are two banks of eight diodes on the board. The lower set are the even numbers from 32-46. These check out fine, reading in one direction. The upper set, odd numbers 31-45, all seem to be bad in that they read in both directions. While I am new to System 11 and not the brightest bulb in the box, I figured that all 8 going south is probably not a coincidence but either a result of the aforementioned coil /transistor or something else upstream that has a problem. One other bit of info, is that I get a momentary short error message when starting up the diagnostics.

Given this, thoughts on possible culprits and things to check? Or do you think replacement of the coil and transistor likely solved this problem?
Thanks

Thanks. I'll give it a try and report back

Man I hate being stupid...you'd think I'd be used to it by now, but I'm not.
The switches seem to work fine, so I was on to check the 1P19 connector. I know that these are also listed in the manual (the 1P prefix) and can see it in the schematic; however, for the life of me I can't figure out exactly where/what these are and how one goes about disconnecting it. I thought perhaps it was the top two connectors of 1J19 since the wire colors matched the schematic but that doesn't seem to be the case if it is, it had no effect (i.e., the right top jet coil did not release)

Thanks, I had the schematic and another site of Sys 11 games but had forgotten about the pinwiki. I'll attack the lights once I get the C side of the A/C issue sorted out. Thanks

Yes, I can find everything. My issue is around understanding where 1P19 is located on the CPU board. I can locate the wire, which is located at 1J19, pin 3 (at least this is what I think it is called). Is this the same location as 1P19-3? Or does 1P19 refer to some other location? It may just be a nomenclature issue.

Thanks! you have helped restore a portion of my remaining sanity.

If I disconnect J19 block the jet bumper releases. So based on the initial response, this would suggest my problem is somewhere on the main board. I'll see if I can decipher the schematics to find the offending component(s)

I saw this on another site but, alas, it really isn't helping me much. Per my earlier post, Q73 was transistor I replaced. Q72 is the transistor in front of that. Seems to test ok, but do you recommend I replace it? I'm not sure how to trouble shoot an issue with U41, U49 or U45. I know it says pin 19 for U41 but beyond that?

OK, so the proper process/sequence is? Go into Diagnostic mode and advance to the A/C testing, DMM set to check DCV, red on pin 19, black on ground, hit the advance to initiate the A/C and I should see ? Just a quick pulse, then back to zero?
Thanks

So here is what I get. Do a coil test. Every A side works fine. Every C side, top right jet locks. Voltage is 10 on an A side coil test and 0 on a C side. This seems backwards to me so I may be doing something wrong; although the jet does fire, so who knows. A/C side test shows same, i.e., 10v on A-side, 0 on C. Another interesting tidbit. If you hit the credit button on the inside of the door, the right sling fires, but no credits. Hmm?

Well, I assume I must have a short somewhere. When I turn it on, the top right jet locks, the Q73 transistor gets hot enough to fry bacon (probably need to replace that again). Are there any typical places/usual culprits to look for a short on one of these 'special' solenoid circuits?
Thanks

To summarize current state. Turn machine on, right jet immediately locks. Disconnect J19p3 and the bumper releases. Voltage at J19p3 is .5. Voltage at pin 19 U41 is steady at 10. I am afraid to go into diagnostics with the coil locked and the transistor U73 cooking.

Thanks, I will replace the 7402. As for the special ones, per the Solenoid table on the inside back cover of the manual, the 6 are left upper jet, left kicker, right upper jet, right kicker, top lower jet and right ramp down, so it is an odd mix. However, if you look at page 95, a schematic labelled Controlled, Special & Switched Solenoids, it shows two groups of 4. One at 50V containing Ramp Diverter, Left kicker, cellar kickback and right kicker. And another group of 4 at 25V with Left top jet, right top jet, lower top jet and right ramp entry down. Everything else I can find suggest only 6 special. But who knows.

Well, I'm not sure of anything at this point, but I believe I am referencing ground and I'm getting 19 VDC. I'll double check once again!

Is it accurate to assume that the issue is on the MPU and not the auxiliary power board?

Yea, that's how I was testing it...both the post and the braid and I get a solid 10vdc on pin 19 of the PIA. As soon as you turn it on, I get 10VDC and the jet locks. Arghh! Stupid question here, but I am testing the physical pin 19. There isn't some sort of logical mapping such that the reference to pin 19 is a logical reference but equates to a different pin position on the PIA. Yea, I know I'm grasping at straws here. So given that I see 10VDC instead of 5, it sounds like the PIA or something upstream of the PIA is the problem, correct?
On the other hand, thanks for the info on eliminating the Aux power from the equation.

First, I really appreciate all your help on this.
OK, so for U41 here are the voltages by pins 2 through 19
2-8.9, 3-7.7, 4-9.5, 5-7.2, 6-8.9, 7-7.1, 8-10, 9-10, 10-3.0, 11-7.7, 12-7.4, 13-6.5, 14-5.3, 15-4.8, 16-7.1, 17, 18 an 19- 10.0

I checked the PIA (u42) below this one and it was registering all 10.0 VDC across all I checked

Well it's clear that I am dealing with several electronic issues... I just not expect the DMM to be one of them. Replaced the battery, no change, so I got another one and, as if by magic, pin 19 registers 5.26 DVC. Hopefully, this means the PIA is OK and it's on to replacement of the aforementioned 7402. Thoughts?
Thanks

Finally had some time to cogitate this whole mess. As it now stands, the coil fires on startup and is in a locked position. The PIA registers and stays at ~5VDC. Since the issue is localized to the MPU and the problem manifests itself at the PIA (no pulse), I assume the PIA is shot. Is it possible that the issue could be somewhere else? Could something be 'telling' the PIA to lock that coil. The reason I ask is that I have a tough enough time soldering a transistor cleanly, I'm pretty sure I'd make a mess of 40 pins. If it is the PIA, I'll need to replace or repair the MPU, which brings up a whole new set of questions like is repair the way to go, who do people recommend, if I have to repair does it make sense to go ahead and try my hand at replacing the PIA or will the cost of repair go up if I butcher it.
Anyhow, one question at a time. Is there anything else I should check before deciding the PIA is the problem? Of course, if you have thoughts on my other questions, I'd like to hear that as well.
Thanks

Well, I have discovered another reason why a coil might lock...it's called replacing a 2N4401 transistor with a 2N5401. Damn that writing is small. Now, in my defense, I did test and compare the new transistor with the ones beside it when I put it in. Everything seemed fine. However, you may remember that my DMM wasn't working properly, so who knows what the readings really were. Turns out I had to replace the 7402 and retested some things in case the locked coil had damaged anything. Well imagine my surprise when my newly installed '4401' wasn't reading like the others. Looking closely, I noticed a 5, not a 4. Replaced the 5401 with the 4401 and viola!, no more locking coil. So lessons learned:
1) I am an idiot
2) get better reading glasses
3) ALWAYS recheck all of your readings and tests when you discover your DMM is not working properly
4) I am an idiot

I still have some issues to address, like lighting and I have a general question about the top jets, but that is a whirlwind specific question. I'm hoping my newly found knowledge will help me muddle through these issues. Thanks for helping me through this quest.