Corrected Schematics for Williams WPC CPU Board

[RacerRik]

Is there an updated version of the WPC schematics available. I had to
repair the CPU board for a Terminator 2 due to battery damage :-
( and I found out the original schematics have several errors in the
circuits for the switch matrix components. It made troubleshooting
quite tricky since I was never sure if the trace was corroded open or
if I was just ringing the wrong points based on schematic errors. I
eventually figured it out by shining light through the board and
following the signal traces but it was such a pain. I came up with
four separate errors in the schematics.

If there is a corrected version out there, I sure would like to have
it for next time. And yes, I know there will be a next time because
I have fixed this board four times in the past and new traces open up
every year or two. I have neutralized the battery electrolyte with
vinegar, and cleaned the board with electronics cleaner, but the
corrosion never stops! Anyone know a way to stop this corrosion
problem from continuing?

Thanks for any suggestions!

[Borygard]

Once the copper of the traces get exposed to the battery alkaline and they
begin to degrade, there's really no stopping it. The area that is affected
will eventually fail. The only thing you can do is identify the traces that
have been damaged and repair or jumper them before they fail.

As for a corrected schematic, I'm not aware of one.
--
Rob Anthony
Pinball Classics
http://LockWhenLit.com
Quality Board Work - In Home Service
314-766-4587

Post by RacerRik
Is there an updated version of the WPC schematics available. I had to
repair the CPU board for a Terminator 2 due to battery damage :-
( and I found out the original schematics have several errors in the
circuits for the switch matrix components. It made troubleshooting
quite tricky since I was never sure if the trace was corroded open or
if I was just ringing the wrong points based on schematic errors. I
eventually figured it out by shining light through the board and
following the signal traces but it was such a pain. I came up with
four separate errors in the schematics.
If there is a corrected version out there, I sure would like to have
it for next time. And yes, I know there will be a next time because
I have fixed this board four times in the past and new traces open up
every year or two. I have neutralized the battery electrolyte with
vinegar, and cleaned the board with electronics cleaner, but the
corrosion never stops! Anyone know a way to stop this corrosion
problem from continuing?
Thanks for any suggestions!

[RacerRik]

Yeah, that seems to be the case. All the traces below the battery
holder (primarily the switch matrix circuits) are degrading over
time. It seems to be slowing down though. The board went for over
three years between something failing this time! I have been using 26
gauge wire wrap on the back side of the board and soldering it from
component leg to component leg. It looks a bit ugly, but it works.
At least it is all on the back side so I don't have to look at it when
I am inside the backbox!!

It sure would make things a bunch easier if there was an updated
schematic available. It took several hours of eye straining to follow
the traces on the board to see where they were supposed to be making a
connection.

Post by Borygard
Once the copper of the traces get exposed to the battery alkaline and they
begin to degrade, there's really no stopping it.  The area that is affected
will eventually fail.  The only thing you can do is identify the traces that
have been damaged and repair or jumper them before they fail.
As for a corrected schematic, I'm not aware of one.
--
Rob Anthony
Pinball Classicshttp://LockWhenLit.com
Quality Board Work - In Home Service
314-766-4587

Is there an updated version of the WPC schematics available.  I had to
repair the CPU board for a Terminator 2  due to battery damage :-
(   and I found out the original schematics have several errors in the
circuits for the switch matrix components.  It made troubleshooting
quite tricky since I was never sure if the trace was corroded open or
if I was just ringing the wrong points based on schematic errors.  I
eventually figured it out by shining light through the board and
following the signal traces but it was such a pain.  I came up with
four separate errors in the schematics.
If there is a corrected version out there, I sure would like to have
it for next time.    And yes, I know there will be a next time because
I have fixed this board four times in the past and new traces open up
every year or two.  I have neutralized the battery electrolyte with
vinegar, and cleaned the board with electronics cleaner, but the
corrosion never stops!  Anyone know a way to stop this corrosion
problem from continuing?
Thanks for any suggestions!

[Rommel]

Hi Rick, why don't you start the ball rolling by publishing what
you've found out alteady.

I'm sure such infirmation would be invaluable to other Pinheads,

Cheers!

R

[beaver]

Here is the errata that I use for the WPC switch matrix:

You need to swap U18A and B, and U17A and B on the schematic.

I found this during my repairs, so I do not know if this is published
anywhere else.

Edward_Cheung CARGPB26

Post by Rommel
Hi Rick, why don't you start the ball rolling by publishing what
you've found out alteady.
I'm sure such infirmation would be invaluable to other Pinheads,
Cheers!
R

[RacerRik]

OK - here are the errors I found:

1st off this is on Williams WPC Schematic Manual - Drawing number
16-9060 Rev 2.

Pin # 9 on J208/J209 (switch row #8) goes to pin #7 of U19 ( not pin
#5 as shown).

Pin # 8 on J208/J209 (switch row #7) goes to pin #5 of U19 ( not pin
#7 as shown).

Pin #1 on U19 goes to pin #8 on U13 (not pin #6 as shown).

Pin #2 on U19 goes to pin #6 on U13 (not pin #8 as shown).

Pin #1 on U18 goes to pin #17 on U13 (not pin #15 as shown).

Pin #2 on U18 goes to pin #15 on U13 (not pin #17 as shown).

My CPU board is the original board in a Terminator 2 game so I am 99%
sure that is the correct schematic for that board. I would certainly
think others know about these schematic errors and they must have a
corrected version to use for board repair. I would sure like to get a
copy of that.

Post by Rommel
Hi Rick, why don't you start the ball rolling by publishing what
you've found out alteady.
I'm sure such infirmation would be invaluable to other Pinheads,
Cheers!
R

[Jack James]

This might help in the future.

Pics of a bare WPC 89 board with all the traces intact.

Jack James

Post by RacerRik
Is there an updated version of the WPC schematics available. I had to
repair the CPU board for a Terminator 2 due to battery damage :-
( and I found out the original schematics have several errors in the
circuits for the switch matrix components. It made troubleshooting
quite tricky since I was never sure if the trace was corroded open or
if I was just ringing the wrong points based on schematic errors. I
eventually figured it out by shining light through the board and
following the signal traces but it was such a pain. I came up with
four separate errors in the schematics.
If there is a corrected version out there, I sure would like to have
it for next time. And yes, I know there will be a next time because
I have fixed this board four times in the past and new traces open up
every year or two. I have neutralized the battery electrolyte with
vinegar, and cleaned the board with electronics cleaner, but the
corrosion never stops! Anyone know a way to stop this corrosion
problem from continuing?
Thanks for any suggestions!

[RacerRik]

Jack,

Was there supposed to be a link to the picture? I don't see
anything. Yes, pictures of the bare board with traces intact would be
very helpful. The battery holder would need to removed, because quite
a few of the corroded traces route under the holder.

So, does a correct schematic not exist, or is no one willing to share
it if thay have one?

Thanks,
Rick

Post by Jack James
This might help in the future.
Pics of a bare WPC 89 board with all the traces intact.
Jack James

Is there an updated version of the WPC schematics available.  I had to
repair the CPU board for a Terminator 2  due to battery damage :-
(   and I found out the original schematics have several errors in the
circuits for the switch matrix components.  It made troubleshooting
quite tricky since I was never sure if the trace was corroded open or
if I was just ringing the wrong points based onschematicerrors.  I
eventually figured it out by shining light through the board and
following the signal traces but it was such a pain.  I came up with
four separate errors in the schematics.
If there is a corrected version out there, I sure would like to have
it for next time.    And yes, I know there will be a next time because
I have fixed this board four times in the past and new traces open up
every year or two.  I have neutralized the battery electrolyte with
vinegar, and cleaned the board with electronics cleaner, but the
corrosion never stops!  Anyone know a way to stop this corrosion
problem from continuing?
Thanks for any suggestions!

[Chris Hibler]

Jack,
Was there supposed to be a link to the picture?  I don't see
anything.  Yes, pictures of the bare board with traces intact would be
very helpful.  The battery holder would need to removed, because quite
a few of the corroded traces route under the holder.
So, does a correct schematic not exist, or is no one willing to share
it if thay have one?
Thanks,
Rick

Post by Jack James
This might help in the future.
Pics of a bare WPC 89 board with all the traces intact.
Jack James

Is there an updated version of the WPC schematics available.  I had to
repair the CPU board for a Terminator 2  due to battery damage :-
(   and I found out the original schematics have several errors in the
circuits for the switch matrix components.  It made troubleshooting
quite tricky since I was never sure if the trace was corroded open or
if I was just ringing the wrong points based onschematicerrors.  I
eventually figured it out by shining light through the board and
following the signal traces but it was such a pain.  I came up with
four separate errors in the schematics.
If there is a corrected version out there, I sure would like to have
it for next time.    And yes, I know there will be a next time because
I have fixed this board four times in the past and new traces open up
every year or two.  I have neutralized the battery electrolyte with
vinegar, and cleaned the board with electronics cleaner, but the
corrosion never stops!  Anyone know a way to stop this corrosion
problem from continuing?
Thanks for any suggestions!

Rick,

The battery holder should have been removed a long time ago... :-)
Mount a remote holder in the backbox.

Here is the link that Jack meant to post...
http://www.pinballenthusiast.com/WPC_CPU/

Good stuff.

I've never seen "corrected" schematics published. I take note when
folks post things here, and I know about a couple of errors in them
myself, but that's about it. I'll have to see if I can dig up my old
notes.

Send me a pic of that MPU...I'd like to see how much trouble you are
going thru.
--
Chris Hibler - CARGPB #31
www.Team-EM.com
http://webpages.charter.net/chibler/Pinball/index.htm

[RacerRik]

Thanks Chris!

Yes, those pics might have helped when I was ringing out the board. I
just glanced at the U19 picture and immediately I see errors... for
instance U19 pin 2 obviously connects to R33 on the board picture.
The schematics show it going to R34....

I don't know how many errors are on the schematic, but what I do know
is the switch matrix circuitry has some significant errors compared to
the real hardware. What they did was swap two of the switch row
inputs on each of the LM339's and then they swapped the outputs back
when routing to the 74LS240s. Since it is a double swap, the CPU sees
the correct input for each switch row. The only issue is when you are
trying to repair the board, since following the schematic leads you on
a wild goose chase - especially when traces are corroded and no longer
making connections where they are supposed to....

I can send you a picture of my MPU board tomorrow, but like I said, it
is fixed for now. I just wanted the schematics for the next time it
breaks!

Rick

[Anthony Quinn]

Post by RacerRik
Thanks Chris!
Yes, those pics might have helped when I was ringing out the board. I
just glanced at the U19 picture and immediately I see errors... for
instance U19 pin 2 obviously connects to R33 on the board picture.
The schematics show it going to R34....
I don't know how many errors are on the schematic, but what I do know
is the switch matrix circuitry has some significant errors compared to
the real hardware. What they did was swap two of the switch row
inputs on each of the LM339's and then they swapped the outputs back
when routing to the 74LS240s. Since it is a double swap, the CPU sees
the correct input for each switch row. The only issue is when you are
trying to repair the board, since following the schematic leads you on
a wild goose chase - especially when traces are corroded and no longer
making connections where they are supposed to....
I can send you a picture of my MPU board tomorrow, but like I said, it
is fixed for now. I just wanted the schematics for the next time it
breaks!
Rick

Hi all,
It is interesting to note that the schematic errors discussed above are NOT present on the Rev 1 version of the Williams WPC Schematic Manual - Drawing number16-9060. I have a 1992 "The Getaway" WPC schematic manual which appears to be 100% accurate.

Regards,
Anthony