U22 Error (WPC-S)


By RonaldRayGun

2 months ago


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  • Latest reply 4 weeks ago by noflip95
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#1 60 days ago

I get U22 Error on startup. U22 is the PIC security chip.

I have low on pins 23,24,25 on U22 which are connected to pins 12,15,16 on U14 (see schematics).
I also have low on pins 14,15,16,17 on U22 which are connected to pins 3,4,7,8 on U24 (note that these are mislabeled as 13,14,17,18 in the schematics).

I have replaced U14 but it didn't change the low pins.
Can I deduce that U22 is bad or is it possible that U24 or U13 are the culprits?

Thanks.

Screenshot from 2017-08-20 16-56-21 (resized).png

#2 60 days ago

Change u22 pic

#3 60 days ago
Quoted from Ballypinball:

Change u22 pic

Thanks mate. I will order a PIC but it'll take a couple of weeks to ship from the US. In the mean time, I was wondering if there could be something else that is causing the problem.

2 weeks later
#4 43 days ago
Quoted from Ballypinball:

Change u22 pic

hmmm... not mandatory

First: indeed there is a big error on WPC-S schematic, the nibbles D0..D3/D4..D7 are inverted on U24. Of course, this is only a pin number error, as D0 goes to D0's CPU. No bus inverted here, only an error on pins numerotation.

The RD wires are the "Read Bus" for the SECURITY PIC. It as two purposes : read the commands/datas from CPU, and read the rows returns from matrix.
If you have RD5..RD7 grounded, you should first suspect U13 74LS240 that is the matrix return (part U13A for the MSB).

Of course, if the PIC (U22) is unable to read commands from CPU, the outputs can have strange behaviour.
First, fix the inputs problem. Note that:
- Deffective U24 has no effect on RD bus, so it is unlikely that this is the case.
- Deffective U23 has also no effect on RD bus.

Check if you see activity on RD0 (U14 pin 9) ~ using a scope, or by default, a voltmeter (any voltage different from 5V or ground):
If yes, this means that the PIC periodicaly read the inputs from U14. Thus, U22 is not dead. It detect command latched (both U14 pin 11 - for the latch - and U22 pin 1 - commands detection), then it read the latch using RA1 port (OC, U14 pin 1).

Usually, when a SECURITY PIC is dead... it is fully dead ! barelly partially. So, if the command detection works... U22 is alive !

Note that... if you really need to replace U22, I well know some French guys that can provide, a personnalized SECURITY CHIP with the serial number you want (and not 999999 or something like)

#5 43 days ago
Quoted from noflip95:

hmmm... not mandatory
First: indeed there is a big error on WPC-S schematic, the nibbles D0..D3/D4..D7 are inverted on U24. Of course, this is only a pin number error, as D0 goes to D0's CPU. No bus inverted here, only an error on pins numerotation.
The RD wires are the "Read Bus" for the SECURITY PIC. It as two purposes : read the commands/datas from CPU, and read the rows returns from matrix.
If you have RD5..RD7 grounded, you should first suspect U13 74LS240 that is the matrix return (part U13A for the MSB).
Of course, if the PIC (U22) is unable to read commands from CPU, the outputs can have strange behaviour.
First, fix the inputs problem. Note that:
- Deffective U24 has no effect on RD bus, so it is unlikely that this is the case.
- Deffective U23 has also no effect on RD bus.
Check if you see activity on RD0 (U14 pin 9) ~ using a scope, or by default, a voltmeter (any voltage different from 5V or ground):
If yes, this means that the PIC periodicaly read the inputs from U14. Thus, U22 is not dead. It detect command latched (both U14 pin 11 - for the latch - and U22 pin 1 - commands detection), then it read the latch using RA1 port (OC, U14 pin 1).
Usually, when a SECURITY PIC is dead... it is fully dead ! barelly partially. So, if the command detection works... U22 is alive !
Note that... if you really need to replace U22, I well know some French guys that can provide, a personnalized SECURITY CHIP with the serial number you want (and not 999999 or something like)

Thanks @noflip95. This is useful info!
I have pulse signal on RD0..RD4, so there is some activity.
I will replace U13 and report back.

#6 37 days ago

The common fault is the two latches ('374s) that are buffering the PIC. Someone shorts coil voltage to the switch matrix, and it takes out the security chip and one or both latches.

Swap in a known good security chip from another game. If it comes up with the game and serial number (vs just 0's) then you know its the first security chip. If its still all 0's, then you know its something else.

-- I provide a "all 9's" version of the replacement security chip.
-- http://www.shiftedbits.com

1 week later
#7 29 days ago

I replaced U13 but still have RD5...RD7 stuck low.

#8 28 days ago
Quoted from RonaldRayGun:

I replaced U13 but still have RD5...RD7 stuck low.

Damn!

There is a trick you can try to identify if the source of the problem, is the PIC or another chip:

- Remove the U22 from its socket.
- Connect a wire (like "Dupont male") between pin 4 (VSS gnd) and pin 7 (RA1 = gate of U14) - blue wire on the picture.
- Connect another wire, between pin 2 (VDD 5 volts) and pin 6 (RA0 = gate of U13) - red wire on the picture.

This will set the U14 to output mode and disable the U13 inputs (return from matrix).
Thus the RD bus, will reflect the input command sent by the the CPU (as U13 is a latch, the command should be visible for a very short time, but enough to be noticeable).

When the CPU start, it first send commands to retrieve the serial number (like 7x commands - thus having RD6, RD5 set to "1").
At startup, if you see some activity on pins 23/24 (RD5/RD6) this means that the issue is the PIC (as U13 and U14 works fine).
If there is no activity, then this means that the problem is somewhere else.

Test_PIC (resized).jpg

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