System 80b help

[dannyc]

Hey guys and gals I have an issue with my Genesis. I had the playfield up and the machine on. I touched something and heard the kickback solenoid click and that was that. So I put down the table and thought nothing more of it. the next time I turned it on the kickout our kickback seleniod the one that captures the ball on the top left corner, started activating like crazy 5 or 6 times like the ball was in it. after the balls were in their spots and the game was ready it stopped and all looked good. However none of the switches at the top count score, same with the pop bumpers. they work but don't score but the out lanes do score. maybe something is not reseting?? I dunno im confused.

 

[Menace]

Sounds like you might have shorted the switch matrix to coil or lamp power and fried a section of the switch matrix. If you don't have a manual I would start by getting one from Steve @ PBR, and then looking at the matrix to see if all the switches that are not working are in the same row or column and try to narrow down a pattern. If you can do that, then all you need to do is figure out which parts are responsible for those group of switches and replace the associated part(s).

You can use the pinwiki for a bit of help but unfortunately it's pretty lacking in the GTB Sys80 repair info.

D

 

[brad808]

Just like menace said try and figure out exactly which switches work and which ones don't. You really need to see the schematic of the switch matrix and you will likely see that either a whole row or whole column will be out. There is a good possibility that z13 or z14 (both 7400) may be dead. I went through a lot of these chips during my first pinball repair ever which happened to be a system 80B switch matrix issue. Those two are the switch return lines. The other problematic spot when the switch matrix gets sent voltage is z15 which is the switch matrix return enable. Here is some information you might find useful while troubleshooting later:

The RIOT Chips.
Chip U4, U5 and U6 are 6532 RIOT chips. These are large 40 pin chips, and often
they fail. If any one of the RIOT chips fails, that can lock up the CPU board. RIOT
U4 handles the switch matrix, and this chip is particularly troublesome. If any of
RIOT U4's input TTL chips at Z11/Z12 (7404 switch strobes/row) and Z13/Z14 (7400
switch returns/columns) fail, this can lock the CPU board. Also the Z15 switch
returns enable chip (7432) can cause switch matrix problems too:
For example, if Z12 is missing or failed, the CPU board will not boot. Also if chip Z14
is missing or failed, the CPU board comes up immediately with "000000" in the
displays (like the slam switch is open). Note row chip Z11 and column chip Z13 can
be missing and the CPU board will still boot (because it doesn't handle the slam
switch).
Switch matrix chips Z13, Z14 (7400 returns/columns) input pins 1,2,4,5,9,10,12,13
can be viewed with a logic probe. They should be strobing, as they are the switch
returns, and connect directly to the playfield switches. None of these should be
stuck low! If one is stuck low, the CPU board may not boot (by forcing the IRQ low).
Then test the Z13, Z14 output pins 3,6,8,11. If these outputs are all strobing, but
an input is not, replace the chip (7400). If neither the input or outputs are strobing,
then the U4 RIOT chip is probably bad. Also note that Z15 (7432) switch enable chip
could be causing problems here too (and this also uses one gate from Z12, pins
12/13).
Strobe/Row Connector Chip In Chip Out to RIOT
S0 A1J5-2/A1J6-1 Z12 pin 2 Z12 pin 1 U4 pin 24
S1 A1J5-3/A1J6-2 Z12 pin 4 Z12 pin 3 U4 pin 23
S2 A1J5-4/A1J6-3 Z11 pin 12 Z11 pin 13 U4 pin 22
S3 A1J5-5/A1J6-4 Z11 pin 10 Z11 pin 11 U4 pin 21
S4 A1J5-6/A1J6-5 Z11 pin 6 Z11 pin 5 U4 pin 19
S5 A1J5-7/A1J6-6 Z11 pin 4 Z11 pin 3 U4 pin 18
S6 A1J6-7 Z11 pin 2 Z11 pin 1 U4 pin 17
S7 A1J5-9/A1J6-8 Z11 pin 8 Z11 pin 9 U4 pin 16
The switch matrix strobes/rows should also be tested. This is mostly chip Z11, with
two gates on Z12 also used. Check Z11's input pins 2,4,6,8,10,12 (these go directly
to the playfield switches). Then check Z11's output pins 1,3,5,9,11,13. Also Z12's
input pins 2,4 and output pins 1,3 should be checked.
In my opinion many offending CPU board issues can be attributed to a failed U4 RIOT
chip. It seems to cause more problems than it should. And often the fail is not black
and white. That is, the game will sometimes boot, but other times may not. This
situation can get worse and worse with time, until finally the game won't boot at all.
It's like the U4 RIOT internally desolves, but at a slow rate. I have seen this many
times, and it's rather odd compared to other manufacturer's games (where they
work one day, and the next day they don't, with no "sometimes it works" factor).

 

[Allan]

Not a fun board to work on RIOT chips allways seemed to run hot hopefuully its a 7404 or 7400 first inline and easier to change.