Yeah, some of the circuits on the PSU carry high voltage to run the display. Just a word of caution, there are hazards for novices that are not trained in electronics: damage to your game and personal injury. Don't forget the warning labels - Danger High Voltages inside.

I am lacking sufficient information to help you because you are jumping past some of my questions. This makes it difficult for me to assist you in diagnosing the problem.

No problem. For IC pinouts, the recessed dot indicates 1, or the pin to the left of the 'top' of the IC as indicated by a notch. When in doubt go by the datasheet, and never trust labels or silkscreen orientation. The datasheet also gives a lot of helpful information about what is expected at each pin and how the IC operates.

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I get in trouble for this all the time

You should not be dropping a volt across the fuse, please check the resistance of that fuse and fuse holder together (game off) measuring with your probes on the outside of the fuse holder. This should only be around 3 tenths of an ohm.

CN6 to pin 2, 1 ohm is close enough - I see no problem there.

Regulator test seems good.

Plug in CPU power (CN6 on the PS) but leave CN2 on the sound board off (removing power from the sound board). If F1 still gets hot or pressing the flippers dumps the game, the sound board is not your problem.

That's odd, but not uncommon... it sounds like the fuse itself could be broken internally. I would also suggest replacing the fuses with new 7A SB fuses while you're at it.

OK...a little baffled at the no continuity comment. Go for the fuse clips, then you can rule those out and continue troubleshooting.

Both fuses should be ice cold all the time anyway, there is nowhere near 7A+ going through them in regular game operation.

The bridge would partially work as a sort of "half wave" rectifier. Maybe the attached diagram will help to give a visual, one cycle would be present - lose a leg (input ac) on one side and that particular cycle is gone. Beyond that the filtering would have a real hard time smoothing the rectifiers output because of the design

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Ok. Good that the fuse no longer heats up.

Does the reset happen only when one flipper is pressed, only both flippers are pressed, or at other random times?

Another thing you can try, clip negative lead of DMM to ground and the positive end of the DMM to the 5V test point on the power supply. Play the game and watch the meter, the voltage should not waver, fluctuate or dip at all. If you see this happen during a reset, you will need more investigation of the power supply.

You have probably checked this already, but anyways.
If there is some kind of connection between the switch of the first 1 of 911 and the flippers,
or there is a bare/semi-broken wire/solder or something like that in close proximity to that switch that are
in line with the flipper wiring..

I assume that a short in that switch (or its near proximity) could cause the pin to reset, that could
also explain the fuses getting hot, right?

If the short is kind of random. The switch it self is could be worn out, or when the switch trigger closes it
could some times touch a screw or another cord or something like that?

What do you guys think?
/mima

OK. I just trying to avoid looking elsewhere until fairly certain that the power supply is good and stable. You've made a number of improvements now and things are certainly looking better there. Flipper supply board is worthy of inspection, certainly - I had not suggested looking at it since you said the switch on 911 caused a reset too. Definitely worth banging around, slapping the game with an open hand and seeing if an association can be found between vibration and resets.

Common problem. Mine had it. Burnt connector to power supply board and GI. Also needed a Bridge Rect. replaced on power supply board.

I posted about 2 years ago with pics. PM for more info. Dont give up. Its a great pin.

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AV8 has a point. I had random resets related to connectors - my Pinbot would reset, very intermittently, until I found that I could lightly press on the PS to MB connector. Repinned the male and female connector and it was rock solid. Even if you have already done this, I would go back and investigate the all the connectors. It doesn't have to be visually broken, even a slight loss of connection due to a fatigued female connector losing some of its spring tension is all it takes to cause a problem.

As for the power supply, you might consider replacing it altogether. If it ends up not a problem you have a spare now, or can be sold for parts or repair to offset the cost. That's what I did with my Taxi.

It's difficult and annoying when it is very random and hard to duplicate a reset. Sometimes you can find a specific correlation between an event easily, other times not so much. Hang in there, you'll learn a lot about your game and its health along the way.

CN1 often has a pin that fries the whole connector. I had to clean that up once because it was causing resets.

--
Rob Anthony
Pinball Classics
http://LockWhenLit.com
Quality Board Work - In Home Service
borygard at gmail dot com

Those are not really "hacks". Not pretty repairs, but look sufficient. Using jumpers is preferred to a lot of the other methods I have seen weekend warriors do. It looks like they were repairing some burnt GI pins (the three off the fuses). From the pics it looks like the board may need some repinning...hard to see how shiny they are from the pics. Probably the female conn. too, especially the J6 you mentioned.

No, it won't matter, they are all tied together at the "input" side to the fuses pins 1 thru 4 at the PS CN8, then the branches are separately fused thru the output pins.

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Doubling up the ground only improves it's effectiveness, it's ability to carry more current. I would have just left it, there is no reason to remove it.

Well, that's really not how it works..."squeezing" another tenth of a volt or even more does no good if it is not stable. If the 4.88vdc at the MPU is stable, it should run without resets. When there is a instability the POR circuit is going to reset the game, and that could happen for any number of reasons. The most common causes is a poor cable, a bad supply, failed diodes allowing coil spikes back into the MPU, or a draw on a poor transformer.

Getting another power supply into the game would have helped reduce the possibilities. Did you already repin the PSU to MPU cabling on both the power supply connector and the connector to the MPU? As Rob posted earlier CN1 is the most common cause.

Tools and parts for repinning connectors is a #1 priority for working on pins.

I was going to suggest if you had access to an old desktop PC power supply you could temporarily use it to bypass the games logic power as a test, but you would need to pin the test supply in to CN17 pins 4,5,and 6 to bypass the games logic supply, and then repin the cable afterwards.

Looking at the video, it does not seem to look stable...there's some significant downward spikes there (but I can't tell what your volts per division setting is)
With a scope on mine, at .01V, my waveform is less jagged than your video shows, and the waveform completely stays within .01V, with no downward spikes during flipping.

As long as your diodes have been replaced on the flippers, still looks like a power supply problem to me.

Anode (Non-banded) side of the diode to ORG/GRY on the left flipper, ORG/VIO on the right flipper.
A failing diode even if installed correctly won't divert the induced voltage from the collapse of the coils back to ground properly. It would probably would only be prevalent on one flipper, but can happen to both flippers.

Short circuit diodes that are not obviously damaged show 0Ω or very low resistance in both forward and reverse directions. Sometimes a diode may become "leaky". While its forward resistance may be normal, its reverse resistance may be lower than the expected infinity. Often this fault could only be measured with the diode removed from the circuit it is working in because of the parallel resistances of other components connected across the diode. The coil is a relatively low resistance, so you will have to remove the diode to check, at least lifting one end. Replacing questionable diodes is the best option.

I have them available, but shipping overseas sucks.

--
Rob Anthony
Pinball Classics
http://LockWhenLit.com
Quality Board Work - In Home Service
borygard at gmail dot com

Glad you figured it out! I feel like I've learned a lot just reading through this whole thread.