TECH: Need Help! Slam Tilt - out of nowhere

[DrFeelgood]

Playing my BOP and the ball interacts with a switch as normal and the
game goes dark for a sec. Upon doing a switch edge test, the switch
registers as a slam tilt ! The slam tilt still registers as itself.
WTF?

[Lloyd Olson]

Slam tilt on coin door, slam tilt on cabinet floor, be sure they aren't
stuck closed or shorted ( even across fiberboard spacers ) after that start
going over normal switch matrix stuff for switch wired wrong, diode
reversed, short to switch wiring, etc. etc. LTG :)

"DrFeelgood" <apol...@mac.com> wrote in message
news:a0b8c08c-13b3-4418...@t41g2000yqt.googlegroups.com...

[DrFeelgood]

Ok. More info. It is the ball lock switches. Where the ball is locked
once kick out of the mout or eyes in the head. O the first switch
registers as "slam tilt" the second as "coin door closed" ???? No
plugs have been undone. How on earth can a playfield switch start
registering as a coin door switch ???

[5voltsr...@gmail.com]

You may have a switch issue. Get your manual out and look to see if
they are in columns or rows. Your U20 on cpu board may have collapsed
or one of the LM339s have gone bad.

[Lloyd Olson]

I suppose you could read my first post. :)

"DrFeelgood" <apol...@mac.com> wrote in message

news:c9974142-101f-4b5a...@q16g2000yqq.googlegroups.com...

[firepower]

This can be one of the most frustrating faults, random slam tilt is
second only to a random game reset you can't track down.

The answer to your question is: Because the "coin door closed" switch
is just part of the switch matrix, which the CPU scans. It isn't a
dedicated switch that connects directly to ground.

When two switches in a row are indicated with one switch closed, check
for a short between the column wires.
If two switches in a column are indicated with one switch closed,
check for short between row wires.

How else can your fault happen?
Well, there is something called the "rectangle effect" where a shorted
switch diode causes one switch closure to be read as another switch.
Can get confusing when this occurs. I'm not sure this is happening
here, but it's worth understanding in case it is.
This explanation is from the BK operator's manual, other examples
exist in WMS trouble shooting guides and probably explained somewhere
in the Marvin's guides:

"Shorted diodes can cause rectangle switch matrix problems as follows:
The lower left 3-bank upper target is down (switch 27), and lower
right 3-bank center target is down (switch 30). A ball enters the
lockup trough making switch 43, a shorted diode at switch 27 would
cause switch 46 Playfield Tilt to be (incorrectly) indicated.
Note that the "rectangle" is always completed with an incorrect switch
diagonally opposite from the switch with the shorted diode."

Download the BK Operator Instruction manual if you want to follow this
description on the BK switch matrix and begin to understand it. The
switch matrix never really changed much on the WMS games, although the
way they were driven by the CPU did somewhat.

As Lloyd and 5v have pointed out, your switch matrix chips may also be
bad on the CPU board. First eliminate that as the problem by
disconnecting the playfield switch ROW and switch COL connectors.
Then use a jumper lead and a diode with the game in switch test. The
banded side of the diode points to the COL connector. I use the
"switch edge test" for this experiment. Details of this method are in
the usual repair guides if you need to follow step-by-step
instructions,

If the CPU board tests out OK like that, then move on to finding the
fault out on the playfield.

Best wishes

-Richard

[firepower]

This is useful information, too. Lots of detail on the switch matrix,
this time WPC:
http://webpages.charter.net/coinopcauldron/wpcswmat.html

-R