(Topic ID: 215939)

Dr who, strange switch matrix behaviour


By jimy_speedt

1 year ago



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  • 15 posts
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  • Latest reply 1 year ago by jimy_speedt
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#1 1 year ago

Hi,

A few days ago, I received the famous "test report" message at machine start. All switches of row 2 were marked as closed on the test switches screen. I replaced the lm339 in U18.

Rebooted. Now I get column 7 closed. Strangely, when I activate one of these switches, for instance a minipf button, the little square displayed on the matrix disappears, showing the switch as open. If I release the button, it show the switch closed again.

I do have the same behaviour with switch 33 enter top ramp opto.

If I remove the 4 connectors at the bottom of the CPU, I potentially expect either the error persisting, or no more error message. I receive "check fuses F114 and F115", which are good !

Can someone give me some help, where should I search ?

Thank you in advance

#2 1 year ago

The Pinwiki has good troubleshooting steps for that message. It indicates the game cannot read your switch matrix normally.
http://www.pinwiki.com/wiki/index.php?title=Williams_WPC#Check_fuses_F114_and_F115_message

#3 1 year ago

Thanks for your reply. I will check this

Now I get this F114 F115 message only if the SM connectors are removed. I would expected that my matrix issue is not linked to bad fuses

#4 1 year ago

if the fuses are good at f114 and f115 then it would mean there is no 12volts going to the switch matrix,test BR1 and see what measurements you get.report back and we will go from there.also check the solder joints that hold BR1 and see if there are any cracks

#5 1 year ago

Thanks. I will do it tomorrow and keep you posted.

#6 1 year ago
Quoted from jimy_speedt:

Thanks. I will do it tomorrow and keep you posted.

sounds good.

#7 1 year ago

Hi,

AC side shows 14,1vac
DC side shows 18,1vdc

Led1 and led6 are lit

#8 1 year ago
Quoted from jimy_speedt:

Hi,
AC side shows 14,1vac
DC side shows 18,1vdc
Led1 and led6 are lit

Ok,Those measurements are correct and BR1 is working proberly.

So turn the game on, set your DMM (digitial multi meter) to AC voltage, put the black lead on ground, and check for AC voltage on either side of fuse f114. You should get about 7 volts AC. This means the fuse is good. Now set your DMM to DC volts, and check for voltage at TP8 (test point 8, located at the right side of the driver board.) There you should see about 18 volts. If these things check out, the bridge BR1 is good. No voltage at TP8? That means BR1 is open. For our repair, TP8 does indeed show about 18 volts, so we know things to this point are OK.
If you follow the schematic along past TP8 (where we know there is voltage), you come across a pair of 1n4004 diodes. We can use our DMM and check voltage on the right banded side of diode D2 (see the video). And sure enough, we get about 17 volts (because these two diodes D1 and D2 drop the voltage about 1/2 volt each, from 18 volts to 17 volts.) Now if we check for voltage at f115 (or TP3), we should see 12 volts. In our case we do not. That means that our problem as to be betwen fuse f115 and diode D2.

So what’s left in the schematic? Well frankly not much! Basically LM7812 and two capacitors. The LM7812 is a voltage regulator, takes the unregulated 17 volts and makes it regulated 12 volts (for the switch matrix.) I don’t think I’ve ever seen one of these fail! But the one thing that does fail in this circuit is what’s shown in the schematic below with the red arrow, a 100 mfd 25 volt capacitor C2. It’s not so much that the cap is no longer working, but what it does as it fails. It leaks it’s electrolyte fluids, which eat the circuit board traces (a lot like battery corrosion), and the circuit goes open. Now there’s no 12 volts, no switch matrix, and you get the “check fuses f114 and f115” error message at game boot up.

the LM7812 voltage regulator is right by fuse f115, and the capacitor C2 is just to the left of the LM7812. If you look at the board, nothing visually seems problematic, as the picture below shows. But don’t be fooled by this
Removing capacitor C2 from the driver board shows that there is indeed a problem. The bottom of the capacitor is physically wet and gross, and the driver board where the cap mounts is discolored.

remember, the game thinks that fuse f114 and/or f115 are a potential issue. These fuses, and this circuit, power the game’s switch matrix. And in the switch matrix, there is one switch (usually switch 24) that is permanently wired closed. That is, the cabling going from the CPU board to the coin door interface board (mounted by the tilt bob) has this switch permanently wired closed.

info was gathered from clay's pinballninja site..great site join up over 800 documented fixes from every game..bally/williams,gottilieb,stern,sega,data east and many more just email clay at cfh@provide.net

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#9 1 year ago

Hi,

It is really kind of you, you spent much time explaining and I will go through carefully.

I actually solved my matrix problem by replacing the ULN2308.

Great support ! Thank you

Jean-michel

#10 1 year ago
Quoted from jimy_speedt:

Hi,
It is really kind of you, you spent much time explaining and I will go through carefully.
I actually solved my matrix problem by replacing the ULN2308.
Great support ! Thank you
Jean-michel

your welcome,have fun

2 weeks later
#11 1 year ago

Hi,

The pin has worked for a few days, then same problem. I ll go through your detailed instructions to find the cause.

Thanks for this valuable help

#12 1 year ago

According to the above, I have checked the f114, D1 diode, tp8 18v and tp3 12v. I do not get exaclty 12v but 11.71vdc

E28F0FA0-2AF4-4153-95D0-07F76B7EC20F (resized).jpeg

1 week later
#13 1 year ago

As I could not figure out what was happening, I purchased a new MPU. Sure the wiring is not responsible.

#14 1 year ago
Quoted from jimy_speedt:

As I could not figure out what was happening, I purchased a new MPU. Sure the wiring is not responsible.

do you test for continuty from the connectors wires to the playfield?to see if there are any breaks,kinks,ect.

#15 1 year ago

Hi,

Yes I did. Now a row is fully lit in addition to the columns partially lit. Cannot be the wiring. Thanks for you answer. Will post as soon as the mpu is replaced

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