I don't see a socket in U50 in your images. Are they images before the repair? Current images of the board are more relevant.

If only the lower slings and flipper relay do not work then suspect U50. If both lower slings and both upper slings (i.e. all four slings) and flipper relay do not work then suspect the only signal common to all of them. That's ~EN and BLANKING. Check for continuity coming in - likely to be correct. Then check for continuity where the signal is distributed. Check them all. You should be systematic and methodical.

EN_SS.jpg

The common signal goes to U45-11 (SST1), U45-6 (SST2), U45-3 (SST3), U45-8 (SST4), U50-3 (SST5) and U50-6 (SST6). As you can see from the image it also goes to U50-8 and U50-9 (flipper relay enable).

There are two paths for the solenoids to fire. One is hardware control from the special solenoid trigger (playfield switch). The other is software control that goes through U49. Both hardware and software meet at U45 and U50. You can bypass U45 and U50 by momentarily grounding the drive transistor (TIP102) tab that should cause the solenoid to fire.

I would disagree. All you need to do is measure continuity. Get your DMM and set it to either beep/buzz/tone if it has such a setting or resistance otherwise. Make sure all the points indicated below are continuous with each other. This means put one lead at one point and the other lead at the other point. Systematically and methodically test each point. You can anchor one lead at one point and then move the other lead to other points.

If you detect a break in continuity you can then apply a binary search algorithm to find the points of failure (i.e. the two points where continuity is broken). Bear in mind that continuity may be broken at MULTIPLE points if there are multiple failures.

If you don't detect and failure then you should check the ~EN signal. This signal originates at U10-19 and terminates at U50-11.

continuity.jpg

Sorry. I made a mistake. It should be U56-6 and not U55-6. It should also be continuous with SR19-5.

I fixed the image. Please test again.

continuity.jpg

Yes. Momentarily ground the driver transistor (TIP102) tab. Solenoids 17 and 18 are not used and will not generate any response. These are Q71 and Q75.

If you get a response then there's nothing wrong with the playfield wiring.

You should then check the hardware (playfield) switch. Momentarily short each individual pin to ground (in the diagram below). Verify that on your board pins 6 and 7 are connected to ground. Some early revisions of System 11 boards have certain things isolated from ground (such as the solenoid ground). You can also use an alternative connection for ground. This activates the playfield switch and should activate the solenoid. If the switch produce the correct result then the problem is not U45 or U50. It's further upstream - presumably at U49. I notice there has been work done at U49 and (unfortunately) I have learned to always question previous board work.

If the switch does not produce a response AND all the continuity is correct (as you have stated) then suspect the ICs. You can swap them shotgun. Otherwise beyond that you will need a logic probe to investigate further.

sst.jpg

Forgot to mention that other simple tests that you can do are to make sure that the supporting components are within specification. The 68 Ohm, 560 Ohm and 2.7k Ohm resistors should measure the same as each other as there are 6 identical circuits. The 68 Ohm and 560 Ohm should measure near those values (there is a 5% tolerance). The 2.7k Ohm resistor often measures lower (around 2k Ohm) because you are measuring them in circuit. It is not common for these components to go bad (unless they are obviously fried). They are easy to check and part of being systematic.

That's good the know. It excludes a simple (but unlikely) cause for the problem. The flipper solenoids will NOT fire because there are no drive transistors for them. The only drive transistor is for the flipper ground relay (2N4401) that is controlled through digital logic. Pressing the flipper cabinet buttons is like grounding the drive transistor as it completes the circuit (and will activate the flipper assuming the flipper ground relay is energized).

Sorry. I forgot to mention that you need to in diagnostic mode for this to work. The EN+SS signal is normally deactivated unless a game is started or in diagnostics. I do a lot of testing and repairs on a bench so I often forget about this when testing at a machine.

I am glad you came to this conclusion. I did not want to suggest it but I have to admit I was thinking this. ChrisHibler is an excellent resource for board repair if you do not know someone local to you.

You are most welcome. I try to help to limit of my understanding and how well I am able to communicate. It seems I often forget about things in my haste to try to help and having done a lot of these things automatically. The most difficult part for me is not knowing the knowledge level and experience of anyone asking for help.

That's unlikely. I have yet to receive a bad IC from a reputable merchant. ICs from different manufacturers may have compatibility issues though but it's extremely unlikely and rare.

The most expedient way to have this resolved is to have a reputable repair technician assess and work on the board. If Chris is unable to handle the board there are also other repair technicians available. If all else fails I also do repairs but it's not my primary focus.