(Topic ID: 191646)

Tilt Immediately at game start but no stuck switches??

By cjs001

2 years ago

Topic Stats

  • 59 posts
  • 10 Pinsiders participating
  • Latest reply 2 years ago by terryb
  • Topic is favorited by 5 Pinsiders


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#2 2 years ago

If you disconnect the wire/capacitor lug from the lower ring around the plumb-bob, does the tilt problem go away?


#4 2 years ago

What happens if you remove the ball from the outhole and start a game - does it still tilt?

#6 2 years ago

A bad diode and/or capacitor somewhere in the switch matrix - test the diode at the outhole switch first.
Do you get any other phantom switches happening during a ball in play?

Did you tinker with anything between it working and not, the previous evening?

#9 2 years ago
Quoted from cjs001:

found that if I push the top right pop bumper it does not fire but it causes the top left to fire instead.

Do both of these upper pop bumpers report the correct respective switch number in switch test mode? Are the solenoids for these activating in correct order in solenoid test mode?

If you disconnect the capacitors from the pop bumpers does the tilt issue go away?

Another thing to try is to start a game and then carefully disconnect the J3 cable from the MPU board live (this disconnects the cabinet switches), does the tilt still activate when the ball goes in the outhole?

Quoted from cjs001:

Also I am confused, if I use my ohm meter to check a diode out of circuit, putting black lead on the diode side with the strip and the red lead on the opposite I get a reading of roughly 600 (1N4004), my meter doesn't give a decimal reading.

Some cheap meters don't show diode forward bias voltage as a decimal place reading, rather the value given is in millivolts. So yours is showing 600mv which is good.

Quoted from cjs001:

Now if I check a diode on a coil in circuit, leads on same sides as stated of diode, my ohm meter buzzes like its a short, is that normal?

Yes, because the ohm meter is giving you the reading of the coil, not the diode. The coil is the path of least resistance.
You can't check a diode in circuit on a coil - you need to disconnect one diode leg off the coil to test the diode.

#15 2 years ago

In switch test mode:
Does the grotto switch report as 32 or 31?
Does the left flipper return lane switch report 24 or 23?

What resistance do you measure with your ohm meter between the orange wire at the left flipper return lane switch and the brown-white wire on the left outlane switch?

If you want to follow plunger069 light socket theory, remove the F1 fuse from the rectifier board so the feature lamps no longer have power.

#22 2 years ago
Quoted from Quench:

What resistance do you measure with your ohm meter between the orange wire at the left flipper return lane switch and the brown-white wire on the left outlane switch?

Quoted from cjs001:

Wasn't fully sure what I was suppose to do for measuring the resistance of the wire on the switch for those lanes.

Put one meter lead on the orange wire, and the other meter lead on the brown-white wire and measure the resistance between them - your symptoms appear to show a short between these two switch return lines.
Measure the resistance with the machine OFF and meter set to 200 ohm range.

Can you post a clear picture of the J2 cable connector at the MPU board?

#25 2 years ago

1) Remove the ball from the outhole and play a ball. Rack up a bunch of bonus. Then drop the ball in the outhole. The game will tilt *BUT* does the game silently countdown the bonus - i.e has it recognised that the outhole switch has closed?

2) In switch test mode, do the switches on row return line 6 report correctly? i.e. tilt switch = 07, left outlane = 23, 5000 arrow lane = 31?

3) Disconnect the J2 connector from the MPU board (so the playfield switches are all disconnected). Power up the game and go to the switch test. If you activate the slam tilt switch on the front door, does it report as 16 or 15? This will hint at whether the problem is on the playfield or the MPU board.

I see your MPU board has suffered from battery corrosion.

#34 2 years ago

So the problem still existed when you disconnected the cabinet switch harness (post #10) and also the playfield switch harness (post #26). Looks like the issue is on your MPU board.

Do me a favour, put all 32 dip switches on the MPU board in the OFF position and tell us if the problem goes away. The dip switches on the MPU board are electrically a part of the entire switch matrix.

#38 2 years ago
Quoted from cjs001:

Could the old socket on U9 cause any of this? Not sure what functions U9 services.

Unlikely to be the U9 socket. U9 is the CPU. Problems there would be much more severe.

You probably have some sort of resistive short between switch return line 6 and 7 on the MPU board so it might be worth taking some measurements and compare readings to other switch return lines (results should all be the same).

Leave all 32 dip switches OFF. Power the machine on and get it in failure mode - leave it powered on a few extra minutes.
Then power the machine off, and remove connector J2 and J3 from the MPU board.

Set your multimeter to 200k ohms mode and measure the resistance between:
a) J3 pin 16 and J3 pin 15 (i.e. one meter lead on pin 16, the other meter lead on pin 15)
b) J3 pin 13 and J3 pin 12
c) J3 pin 10 and J3 pin 9
Are all results the same or is the first measurement lower?

Now measure the resistance between these signals on the 6820 PIA chip at U10 between:
d) pin 17 and pin 16 (i.e. one meter lead on pin 17, the other meter lead on pin 16)
e) pin 14 and pin 13
f) pin 11 and pin 10
Are all results the same or is the first measurement is lower?

Report all the readings.
For reference, two of my boards on the bench measure around 95k-100k ohms at all these locations.

Similar to terryb's comment, I'd probably suspect conductive corrosive residue between pins under the dip switch blocks - see pic below:


#40 2 years ago

Do the tests first. Would be nice to diagnose and see if you can measure an anomaly.

#44 2 years ago

Excellent, that definitely shows a resistive short between switch return line 6 and 7 on the MPU board which explains your problem.

First off try swapping the two 6820 PIA chips around at U10 and U11 and see if it makes any difference.

Regardless of whether the PIA swap works, you will need to remove, clean the corrosion under the dip switch block area and install new dip switches because this is very much where the problem likely exists or may cause problems in future.

#46 2 years ago
Quoted from cjs001:

could the short be in the PIA itself

There's a tiny possibility the short is inside the PIA - that's why I mentioned changing it just in case. Install a spare since you have them. U10 is the one controlling the switches.

I suggest you deal with all four of those dip switch blocks. You can remove and clean the area first and then test it without the dip switches if you don't have any on hand (they'll simply all be detected as Off).
When you remove the switches, take some photos of the PCB area and bottom of the actual switches for our curiosity.

Good luck!

#49 2 years ago

What resistance do you now measure between U10 pins 17&16 ? (you were getting 1.1k - 1.4k when really it should be around 100k)

The problem might be cruft under another switch block if removing this one has made no/little difference to the short.

Quoted from terryb:

Quench has you on the correct path so I don't mean to sidetrack things

Terry, your input is always appreciated

#51 2 years ago
Quoted from cjs001:

I am getting 114.9 now at pins 17&16 with the PIA out currently.

That's a pretty good sign.

Out if interest, what do you measure on the actual PIA chip (pins 17&16) out of circuit?

#53 2 years ago
Quoted from cjs001:

On original one out of circuit I am getting nothing. Meter just stays at 1.

That's what I get - it's probably safe to say it's not the PIA chip at fault.

#55 2 years ago

Great stuff. Sounds very promising. Those switch block areas on the board definitely needed attention.

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