Asteroids T/S

Talon2000

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I'm still trying to learn all this, so please bare with me. Basically I'm trying to figure out the best way to troubleshoot Asteroids boards. It shouldn't be as difficult as I'm making it out to be, or is it?

Ok I've got several asteroids boards with the same symtoms.

Test mode comes up good.
No Ram errors, No rom errors.
But under normal game play, get constant reset on pin 40of the CPU

Currently just trying to learn how to trouble shoot 1 board, so I haven't done all these test on the rest yet.

Have done the following
Verified Rom sigs with Fluke
Verified Ram with Fluke
Verified Bus with Fluke
Have written the following AVG test program to get + sign with Fluke
And well I get the + Sign.

WRITE @ 4000 = FF
WRITE @ 4001 = A3
WRITE @ 4002 = 00
WRITE @ 4003 = 02
WRITE @ 4004 = FF
WRITE @ 4005 = 97
WRITE @ 4006 = 00
WRITE @ 4007 = 90
WRITE @ 4008 = 00
WRITE @ 4009 = A2
WRITE @ 400A = 00
WRITE @ 400B = 00
WRITE @ 400C = 00
WRITE @ 400D = 90
WRITE @ 400E = FF
WRITE @ 400F = 33
WRITE @ 4010 = 00
WRITE @ 4011 = E0
DPY-CONFIRM PLUS PATTERN. CONT#
DPY-+=EXIT%1#
0: LABEL 0
WRITE @ 3000 = 00
IF REG1 = 25 GOTO 2
GOTO 0
2: LABEL 2
DPY-##

Went ahead and did sig analysis with the catbox to double check the address lines, and data lines.
Ran Sig analysis on the VG Address selector,and address generator.

I'm assuming since the sigs are good for those two areas, that the VG program counter is functioning correctly?

I don't have sigs for the vector generator buffer, I'll have to work on that since I have several revision boards, some with R2, and some with P2. But I'm getting out what is going in, so I assume the buffer is ok.

I've removed pin 10 of A9 (halt) and CPU still resets
I then removed pin 1 of L6 (DMAGO) and CPU still resets.

So it sounds like I have an MPU problem, but I'm not sure where to go from here.

Does that sound about right, or am I just not getting it..
 
Ok I've got several asteroids boards with the same symtoms.

what are the chances of that?

i would make sure you have the right voltages going to the right places. could be you have a power supply problem and it causing the same problems with all your boards?

or do you have a working board and all the other ones are failing in the same way?
 
I have 5 working boards. Plus I have a re-built ar board, and power supply on my test bench I'm using.

So it's not a power supply problem.

Previous symptoms on other boards were bad roms, bad rams, bad cpu's, I've managed to get them all to the point where they run the test mode, and don't have ram/rom/bus errors.

It's trouble shooting the remaining MPU, and VG problems that I'm not clear on.
 
Are you using the same rom set to test all of the boards? Maybe a bad rom set? The speed of the VG eprom is also important.

You can't mix revs of the roms. There is documentation for what rom revs work in what board versions and which work together.

Beyond that I will check my notes when I have time this week.

If it's multiple boards with the same problem, it helps. Are all of the boards the same rev, like "-05"?

Bill
 
Each board has is own rom set, I have Rev 4, and Rev 5 boards. The rom locations on 5 are different and are placed correctly. Rom speed shouldn't be an issue since they are original roms. They are all rev 2 as well.
 
I didn't think much about that circuit, until I read the description of it, and found out that under test mode, it get's disabled. Doing the L6 pin 1 trick showed that it was on the MPU side, so I just started checking the parts of the circuit that don't get checked by signature analysis.
 
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