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WWF Wrestlefest that does nothing.

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aapuzzo

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I purchased a few boards so I can practice learning how to troubleshoot arcade games. This one is a Wrestlefest that was "untested" from eBay. When I plug it the supergun I can see the screen pop like it registered power was plugged in and nothing else happens. I dumped all ROMs except IC 0 and 1 because I don't know what to set my programmer for. The CPU ICs where the only ones that didn't cross reference with MAME so I rogrammed them US set 1 and it did not help. I was curious about the original ROMs so I combined all ROMs I dumped with ic1 and ic0 from an internet downloaded romset. The game works and I can start a match. I can't seem to find a schematic from this board. The board is very clean and checked anything on the PCB that looked like a scratch. What should I try next?
 
You should start by checking the clock, reset and halt pins of the 68k cpu with your logic probe. clock should be pulsing, reset and halt should start out low when you power on the board, then verify quickly switch to and stay high.
 
ack said:
You should start by checking the clock, reset and halt pins of the 68k cpu with your logic probe. clock should be pulsing, reset and halt should start out low when you power on the board, then verify quickly switch to and stay high.
Click to expand...
Thanks I'll check it out. Is there any issue with attaching the logic probe to the +5 and ground on the power supply instead of finding point on the board? This board I can't find a good place to clip on and I don't want to short something out if it falls off. It would be much safer to just screw it down under the terminals as a second wire. Otherwise I'll just solder on a lead. off one of the caps.
 
As far as I know that should be ok. Long term you should consider modifying your logic probe to have smaller clips. The ones it comes with are annoying to deal with. This is what I did with both of my logic probes.

IMG_1288.jpg

The clips are small enough to grab individual vcc/gnd legs of most dip components.
 
Thanks I'll check this out when I get back home. I was thinking I like the ones on my oscilloscope more.
 
I have a plug on my psu cable to directly plu in the probe. Also have an extened ground cable on there to connect the oscilloscope ground to.
 
So I was able to test it.

MC68000
Pin 15 CLK = Dead No light or tone low or high but CMOS light is flashing. Its like it has a weak voltage.
Pin 17 Halt for .25 seconds starts low and goes high
Pin 18 Reset starts low and goes high

I don't have a real pulse on any pin except 20.
 
I'm finding Winbond W27c020-70 on ebay that some people are listing as One Time Program and others as EEPROMs. From the datasheets at Winbond it looks list all W27c020 as electrically erasable? They are faster 70ns. Any reason not to go with these over a traditional UV EPROM? Easier to erase and probably newer.
 
I reprogrammed the existing chips using the code from above. Black screen & no sound.
 
With a PC I know bad or not properly seated ram would cause this. Does the same go for arcade PCBs?
 
@ack I'm going to try and use what you thought me before. I might be on the right track with the RAM. IC16 and IC17 RAM chips UM6264k-10L have pin 22 OE set to low.

The UM6264k-10L chips at IC31 and IC32 for pin 22 OE are high. I think it's supposed to be OE active low to enable the chip if that's what the line over the OE means on the data sheet. If that is the case I need to find out why IC 31 and 32 aren't going high and follow those traces.
 
looks like IC31 and IC32 OE 22 run to IC45 Pin 2 which is a 74LS04 that simply inverses the logic from pin 1 in the same chipIC45. So if Pin 1 is low the Output Pin 2 is high. This seems to be working correctly. iIt must be further upstream from PIN 1 on IC45 unless I am chasing a ghost and looking into the completely wrong thing. I really wish I had a schematic.
 
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1C45 pin 1 goes The following 2 chips but these don't look like output pins. With the traces running under things and no schematic I'm having a hard time finding out where they are getting feed from.

HD74LS244P
IC48 pin 6 - Input Pin

SN74LS32
IC61 pin 2 - Input Pin 1B
pin 5 - Input Pin 2B
 
This situation is a little different then the double dragon board. You were running the diag rom I modified which was constantly doing reads on the work ram. So work ram should have been getting enabled.

What do you see on the data/address lines of the cpu? do they pulse, low, high, or dead?

Does your TV get a signal when the board is powered on?
 
ack said:
This situation is a little different then the double dragon board. You were running the diag rom I modified which was constantly doing reads on the work ram. So work ram should have been getting enabled.

What do you see on the data/address lines of the cpu? do they pulse, low, high, or dead?

Does your TV get a signal when the board is powered on?
Click to expand...
My TV makes a pop and the screen flickers like a switch was turned on.

MC68000 Probe results
1 – L
2 – L
3 – H
4 – L
5 – H
6 – L
7 – L
8 – L
9 – L
10 – H
11 - H
12 - H
13 - H
14 - H
15 – Cmos
16 – L
17 – H
18 – H
19 – H
20 - LH Cmos
21 - H
22 - H
23 - H
24 - H
25 - H
26 - H
27 - L
28 - H
29 - L
30 - L
31- L
32 - L
33 – L
34 – L
35 – L
36 – L
37 – L
38 – L
39 – L
40 – L
41 – L
42 – L
43 – L
44 - L
45 - L
46 - H
47 - H
48 - L
49 - H
50 - L
51 – L
52 - L
53 - L
54 – H
55 – H
56 – H
57 – H
58 – H
59 – H
60 – H
61 – H
62 – H
63 - H
64 - L
 
Hrm according to that the cpu is attempting to write 0xffc5 to address 0x0c0000 (start of fg tile ram). This seems to be valid as I see the same write in mame. I don't know enough about the 68000 cpu to know why it would stall like that. HALT is high so the cpu isnt halted. Perhaps its waiting for a DTACK signal?
 
Yeah there is probably something bigger wrong with this one. I may have to throw in the towel or start replacing everything which probably isn't worth it. Without the schematic it's really difficult. I'm looking at the large square tj0002 chip and it looks like somebody may have reheated the pins for a reason. I'll try and buy another broken board online that is missing some textures and has a schematic to try and learn more with. Thanks for the help again!
 
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As I read up more on why the 68000 would stall like that I'm pretty positive its waiting for DTACK to go low. It looks like that signal comes from PIN 3 on IC50 (74LS00), which is a quad 2-input NAND gate. Try checking the 2 inputs that are used to determine the output state of pin 3 against the truth table for the 74LS00. If that looks correct, determine which of the input pins would need to change state to make pin 3 go low and work you way backwards from that.
 
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