Super Off Road Track Pack Help.

[ArcadEd]

I have started a few threads at KLOV asking for help repairing my PCB.  However, I tend to get side tracked and just start posting all kinds of information.  What I would like to do in this thread is ask someone like RJ to simply walk me through trying to fix my PCB.  I enjoy fixing PCBs and I am willing to spend some money on equipment if I need it.  I have most of the equipment now. 

I am going to start off by giving a little bit of detail on the PCB from CAESAR.
cpu: 80186, 16MHz
cpu: Z80, 6MHz
cpu: Z80, 6MHz
audio: AY-3-8910A, 1.666666MHz
audio: AY-3-8910A, 1.666666MHz
audio: Leland 80186 DAC


I have Schematics via the Manual.

Master CPU is Z80 at U99
Slave CPU is Z80 at U1
80186 Handles Audio I presume?

The PCB is setup with a top and bottom board, with Ribbon cables going between the two.  The actual Z80s are on the Top board.  I have tried replacing ribbon cables.

With that said, I am going to walk through RJs pcb repair tutorial 101 and 201 and report back my findings here, and nothing more.

Thanks upfront to anyone willing to help.

[ArcadEd]

I have visually inspected the board and I don't see any missing parts, scratches, trace breaks, etc.

I pressed down on all ICs, no change on screen.  Here is a picture of the screen currently.

Power Supply reading on Power Supply is 5.55v

On top board it's 5.16v (Recommened for this game is 5.20)
Bottom Board is 4.96

I have removed the 12v from the PS because cranking the PS up to high to get a good voltage on the board makes the 12v in the 15v range.   I am pretty sure the 12v is just for sound.

[ArcadEd]

Probing the Z80s CPUs.

Master CPU
Halt - LOW
Clock - LOW/HIGH
Reset - HIGH

Slave CPU
Halt - HIGH
Clock - LOW/HIGH
Reset - LOW

Same measurements on the bottom board where the CPU ribbon cables plug in.

I will wait for instructions/advice now.  I have my schematics showing me where the Master CPU PROM/RAM are located if that's next.

[jay]

I am certainly not RJ

Are you certain the problem is not with the monitor.

[ArcadEd]

Yes, monitor is fine.  It's my test bench and I have another super off road board that boots up just fine with it.

[ArcadEd]

I don't know if this is relevant at all, but thought I would share. 

I replaced the 4 4464 RAMs on the bottom board and it changed my picture.  I have my garage door open so there is more light coming in, but he pattern is completely different now.

[ArcadEd]

Well, to add complication I found out that the power supply on my test bench was wack.  It was putting out almost 15v on the 12v line.  I was trying to fix another off road board with just a sound problem and couldn't figure out why one of the sound ROMS kept getting corrupted. 

So now I will recheck all roms on my board with a new power supply and see what's up.

[ArcadEd]

All Roms are good.

As far as I can tell, the master CPU is booting up and running. With my probe I can see the address and data lines sending data moving from nothing, to high and low.

I assume now is to get the slave cpu up and running?

That one shows RESET as LOW right now.