You will run into problems using sys 11 boards in a 11c game. But any 11a, 11A, 11B board would work in a 11c game , I'm pretty sure. Someone correct me here if I am totally wrong.

Sys11 board can be used in 11c with modifications, mainly on the special solenoid inputs. I don't remember if it also requires a jumper change but that may be if you try to use it in a Sys9 game.

viperrwk

According to Pinwiki, a few mods are necessary to use a sys11 with a later revision game, but it depends on which revision -

There is a later revision available which has an additional jumper W16 located between the 7 digit display and the relay. This early pcb has a trace routing error to the sound ribbon cable connector. If you use it with a later system 11A sound card you will get no sound because the sound card doesn't get reset properly. If you wonder why your High Speed doesn't beep when turning it on this one is also the culprit

http://www.pinwiki.com/wiki/index.php?title=Williams_System_9_-_11

I think I remember reading there are some possible grounding things you have to do as well.

The details are in Clay's guide.

viperrwk

Truth be told, you can mod any series sys 11 board to work in any sys 11 game. Problem is, is it worth modding what you have or, just finding the correct revision board? Additional problem is, that it will likely be a different amount of time/work for each given game/series of board you are trying to swap and the average "tinkerer" isn't going to know what work is involved.

SYSTEM11 MPUs are kind of a can of worms:::>

Changing CPU boards among Early System 11 games:
High Speed, Grand Lizard and Road Kings do not use ground at the CPU connector 1J18, pins 6,7. If you try and use this older System 11 CPU board in a newer System 11A game (no liability accepted if you try it), you will have to run a ground wire to connector 1J18 pins 6,7. Otherwise, your special solenoids will not work.

Here's the 4 different generation of baords:
System 11: First generation of system 11.

System 11A: Second generation of system 11. System 11A boards can be used in system 11 games too.

System 11B: Third generation of system 11. Actually there were two version of System 11B boards, with the first version having the sound amplifier at U1 (a TDA2002). Special solenoids now CPU controlled and games have Auxiliary power driver board (actually these both started with "Big Guns, the last system 11A game).

System 11C: Fourth generation of system 11. System 11C boards can only be used in system 11C games because all sound circuits have been removed from the CPU board. There are no ROMs at U21 and U22, and most of the circuitry from the top left corner of the board has been moved to the sound board.

--->The below statement is very misleading<--
"The most flexible CPU is system 11B. This board can be used in system 11, 11A, 11B or even 11C. To use a system 11B board in a system 11C game, you just don't use connectors 1J16 (volume control) and 1J15 (speakers) on the system 11B board. Also the sound ROMs at U21 and U22 are not used, since they are moved to the sound board."

The reason it's misleading.....

IF YOU HAVE A STRAINGHT 11 BOARD, and are aware of the additional ground needed at 1J18 pins 6+7, A STRAIGHT SYS11 BOARD IS IN FACT THE MOST FLEXIBLE OF THE SYS 11 BOARDS.

So, to answer your question: If you can add a ground to 1J18 pins 6+7, your straight system 11 board should work in an 11C game.

But honestly, that's kind of a waste since there is certainly someone that needs that plain system11 board in the world and that's the only one that can work properly in their game. Also, you would not be using ANY of the sound portions of the MPU; it would all just be sitting there looking pretty and never used.

I have an issue with my GL that not all the sounds play. Could that be fixed by replacing the board?

It depends on what sounds are missing. The background music is handled by a dedicated sound board.

It would help if you can go into sound test and relay what sound do and do not play. Is it speech, background, specific call outs? More details are required to diagnose your problem correctly.

Speech. I think. How many different songs are there?

The main music plays and the multiball chant.

But much of the wildlife call outs are missing. Monkeys... the lizard "roar" when you light the eyes... etc. All I get is flashers clicking when you roll the two ramps over or get the multiplier. I'm not sure if the spinner makes a sound but I believe that's gone too.