Midway Gunfight wrong bars appear with or without ROMS

Call Sign ACE

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Midway Gunfight wrong bars appear with or without ROMS

The game has alternating wide black bars and narrower white bars with lines through them. The white bars with the lines through them scroll up or down as if there's some kind of sinc problem.

The same bars appear all the time no matter if there are any ROM inserted or not.

Does anyone have any idea what might be the problem?

I have socketed and replaced many chips on the board and have replaced the CPU.
 
sounds like your game is not loading the program. check after the buffer on the cpu of the address line a13 and see if that is stuck or something see if the output mimics the input if that is ok I will tell you what pins to look at later at the multiplexer that control the loading of the program into memmory right now I am not near any schematics for that game and doing this from memmory I think the buffer chip is f3 output is pin 6 and 4 and 5 are inputs and tied together
 
I just repaired a similar issue on a Boot Hill. Turned out to be the 6000uF cap on the power supply board was bad. My voltmeter showed the 12V to be OK but when I looked on a scope there was several volts of ripple. Maybe a long shot but I would definitely verify ALL the ps voltages. You can use the AC setting on your meter to measure the ripple voltage.
 
I checked the a13 line and it is pulsing. The LS153 chips are stuck low on pins 2 and 14 also the D3 line has no pulse on the 74174 at Location D7 as well as the 8216 and the CPU. I have replaced all the corresponding chips to no effect.

I should have good power since I have installed a switching power supply with adapter.
 
The processor reset circuit on this game is on the power supply board. What did you do with that signal since you are not using the original PS? If the processor isn't getting a reset pulse AFTER all 3 power supply voltages are up and running it will likely be executing random code. (not running the game code properly). You can try pulling that line to +5V then ground AFTER the game is powered up to see if it starts executing properly.
 
toledo is right about pin 10 on the input edge connector for the main board when you start up you must give it a pulse to 5 volts then ground it to go to run mode if you are not using a midway power supply with reset signal.

with no power on test conductivity of the 153 pin 2 and 14 to see if they are connected to gnd also check d3 line if that is connected to gnd. with the board powered and pins 14 and 2 gnd you are also connecting the daughter board to the buss lines but since you also said the cpu was wead for d3 then the 8216 at d3 is probably shorted or has a shorted trace so if d3 is socketed remove and test continuity to gnd with no power.
just saw the line about the ps with I hope the midway adapter. see if cpu data lines all work with the 8216 removed
 
I removed the 8216 at D3. The bidirectional line on pin 6 shows high/low pulse. The other lines at pins 3, 10, and 13 show a low pulse although pin 10 has intermittently pulsed high/low.

I will check the reset again, but I have an adapter installed that creates a reset from the switching power supply and it did check good before.

I should mention that the previous switching power supply that I used malfunctioned and put out 32 volts on the 12 volt line. Not sure what this would have damaged. After the power supply was replaced I did have almost the proper bars according to the manual but then began experiencing other problems that were corrected but now stuck with the strange bars that it now has.
 
the voltage problem could damage the roms. the memory and the cpu.. you are going to have to determine where the short is that is taking down the D3 data line to the 174 chip. you might have to scrape a trace or cut a pin on the D3 data bus line that can easily be patched until you find what is grounding out that data line. might be the 174. have to attack this one step at a time fixing what we see and how it effects other things. the 174 feeds d6 which controls the pins 14 and 2 of the 153. d6 is also connected too address line 13.
 
32V on the 12V!!!! for how long? If it REALLY was 32V you likely destroyed the 8080, rams and roms. Be prepared for a long road to recovery for this board. If you are lucky it wasn't really 32V and was loaded by the board to closer to 12V. Did you actually measure 32V with the board connected?
 
just had another thought on a dead D3 data line. you can have a shorted ram chip of h11 or g11 or you can have a shorted chip on the daughter board. just for peace of mind disconnect the daughter board and check position 27 on the edge for conductivity to gnd. I don't have any schematics for the daughterboard so i cant give clues there. and another quick question. monitor pin 1 on c3 on powerup and tell me what it does. with chip d3 out is the socket pin 12 shorted?
 
It's been so long and I've been over so much with this board but what I remember is that I measured 32V at the edge connector.

Even so, after I replaced the power supply I did manage to achieve almost the correct bars until other things went wrong, so I figured the ROMS and RAMS couldn't have been completely destroyed.

I also had a short on the board near the RAMS that I fixed.

One other strange thing is that the ROMS have always run very hot. If you were to hold your finger on them it would become to hot to touch. Is this normal?

They did this even when the game was running correctly except for the gun movement.
 
gun movements come from the daughterboard over the data bus which means the main logic board could work perfectly but inputs might not be getting encoded properly into the bus to make the game work. roms do get warm.

with no power are either pins 14 or 2 of the 153 chips have continuity to gnd?
 
No.
Pins 2 and 14 of the 153s do not show continuity to ground when not powered up.

Although they are stuck low when powered up, none of the various lines that show problems appear to be shorted to Vcc or ground, since they all show on the logic probe that they are able to be pulsed with a logic pulser.
 
Outputs on pins on chip D6 are stuck and the test manual says they should have pulses. I changed the chip as well as chip D7 but no change. I changed chip F3 but no change and chip B4 tests good with a logic comparator.

I removed pin 9 of chip C2 which brought back a pulse on the pin 13 data line at the 8216 chip at at location D3 as well as all the other chips that it feeds to.

I found that pin 10 on the LS153 at location C2 is stuck low. This is traced back through an LS00 at location BX which appears good, which then traces back to a 9316 chip at location E7 which shows all outputs stuck low, even though the chip has been replaced.

The schematic shows these pins of the 9316 running to the sounds on the daughter board as well. Could this be causing the problem? I can't figure out what else could be causing this.
 
for d6 is 5 6 8 9 2 and 3 pulsing? trying to figure if that chip has good and proper inputs. if they are good and pulsing maybe one of the inputs on the 153 is bad and causing a the outputs for d6 to be pulled low. personally I would snip the inputs to the at pin 14 on each 153 starting at c2 one at a time until I got pulsing back at the corresponding d6 output. then when the bad chip is found I would resolder the cut pins one at a time checking for an change. I don't want to get to far a field in solving more then 1 problem at a time but in answer to your question about the daughter board causing problems on the main cpu the answer is yes. I have temporarily removed this problem by using an exacto knife to cut the trace on the daughter board. the main board will work with this temporarily disabled. concentrate on main board first.

question is pin 9 killing the data line 3 because pin 10 on c2 is stuck low and pulling its output 9 low. reconnect pin 9 and cut pin 10 going into c2. does data 3 work now? check this first before starting to cut the 153 pins going to 14 and 2 but only cut the pins 14 and 2 if you confirm that the inputs to d6 are good and pulsing.


what roms chips are you using? are they original non programmable roms or has your board been rewired to accept eproms?
 
Bizarre testing results. What is the problem?

Sorry for not posting sooner, I haven't been able to get back to working on it lately.

I have found some very strange happenings on this board that I have not been able to figure out.

Chip D6 has output pin 4 stuck low and input pins 5 & 6 stuck high. When I pulse pin 5 and probe pin 4 I get a pulse. But when I pulse pin 6 and probe pin 4 I don't get any pulse. When finding this out I then socketed and replaced the chip but the problem remains.

I also found that a pulse goes from pin 5 to 6 but not back from pin 6 to 5. These shouldn't even be connected. It can't be an internal short since I replaced the chip.

This same thing also happens on chip D7. I get a pulse from output 2 to 12 and not from 12 to 2. This chip was also replaced with no result.

These pins also should not be connected. I then suspected an external short so I then turned off the power and checked for continuity with a meter but it shows no continuity.

What is going on here? What could be causing this?
 
I don't understand you pin 5 6 dilemma. 5 on d6 is fed from d7 2 and 6 is fed from d7 12.

I would think when you pulse 6 that 5 stays high so 4 should stay low if you ground 5 6 goes down too to make 4 high. try removing the daughter board both 5 and 6 go off the main board to the daughter which I have no schematics too but the daughter board might have the fault.
 
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