1943 - Battle of Midway (Bootleg)
Another recent pick up from a batch of pcb's from alpha1 with this one reported as not booting.
Arrived in petty good condition, with no obvious issues at first glance. No shorts on the board so powered it up and absolutely nothing. Black screen, no sound. Nothing.
Had this a few times and it's been a missing or broken crystal so that's the first place I looked and the crystal was present and correct but there was a broken resistor next to it with the leg on one side being completely disconnected, like it just popped out
With that resistor snapped, the feedback loop between the inverter and the crystal was broken, so the oscillator couldn’t run and hence the game was dead. Once replaced, the game sprung to life .....
First glance everything looked good. But if you look very closely at the 1943 logo and in the battle of midway wording, there are a few incorrect pixels knocking about. Also on the odd bit of other text here and there. Might not come across well on these pictures but they were and they were bugging me. At first I thought maybe just a bootleg thing so I checked on mame and a few videos online and didn't see it on others.
Got a bit lucky here because there are only 2 socketed ROMS on this board (1 and 4). With ROM 4 being the character/text layer which surely holds the logo... so I popped it out and read it and it didn't identify so I verified it against the ROM 4 data in the 1943b rom set and this mask rom has permanent data errors (42 bad bits vs known good). Likely failed cells in the mask rom.
Burned a new 27C256 with the (4.5h) rom data to see if this would clean up the rogue pixels and it did.
Sounds were present but replaced a blown cap in the audio circuity which can only help. (below left)
Also very nearly replaced the broken trace shown (below right) until I realised it had to have been done purposefully as it would make a direct connection between +5v and Ground if bridged. Instead I scraped the traces back closer to the via's and popped in a decoupling cap to cover it and stop anyone in the future seeing that broken trace and thinking it needs repairing!!
My OCD is not a fan of long trace repair wires either and if I can tidy them up I will. Both for aesthetic reasons as well as practical. The solder side of this top pcb had a longish one I found could have a much smaller option to repair the damaged trace which must be under the body of IC. Anyway, tidied up with a smaller repair and much less chance of that getting caught and being ripped off its solder points than the smaller replacement , and it just looks better .. tried to illustrate where those wires were/are below.
Not really part of the 'fix' I know, more just maintenance I suppose.
So that's this one back to 100% working again.
Another recent pick up from a batch of pcb's from alpha1 with this one reported as not booting.
Arrived in petty good condition, with no obvious issues at first glance. No shorts on the board so powered it up and absolutely nothing. Black screen, no sound. Nothing.
Had this a few times and it's been a missing or broken crystal so that's the first place I looked and the crystal was present and correct but there was a broken resistor next to it with the leg on one side being completely disconnected, like it just popped out
With that resistor snapped, the feedback loop between the inverter and the crystal was broken, so the oscillator couldn’t run and hence the game was dead. Once replaced, the game sprung to life .....
First glance everything looked good. But if you look very closely at the 1943 logo and in the battle of midway wording, there are a few incorrect pixels knocking about. Also on the odd bit of other text here and there. Might not come across well on these pictures but they were and they were bugging me. At first I thought maybe just a bootleg thing so I checked on mame and a few videos online and didn't see it on others.
Got a bit lucky here because there are only 2 socketed ROMS on this board (1 and 4). With ROM 4 being the character/text layer which surely holds the logo... so I popped it out and read it and it didn't identify so I verified it against the ROM 4 data in the 1943b rom set and this mask rom has permanent data errors (42 bad bits vs known good). Likely failed cells in the mask rom.
Burned a new 27C256 with the (4.5h) rom data to see if this would clean up the rogue pixels and it did.
Sounds were present but replaced a blown cap in the audio circuity which can only help. (below left)
Also very nearly replaced the broken trace shown (below right) until I realised it had to have been done purposefully as it would make a direct connection between +5v and Ground if bridged. Instead I scraped the traces back closer to the via's and popped in a decoupling cap to cover it and stop anyone in the future seeing that broken trace and thinking it needs repairing!!
My OCD is not a fan of long trace repair wires either and if I can tidy them up I will. Both for aesthetic reasons as well as practical. The solder side of this top pcb had a longish one I found could have a much smaller option to repair the damaged trace which must be under the body of IC. Anyway, tidied up with a smaller repair and much less chance of that getting caught and being ripped off its solder points than the smaller replacement , and it just looks better .. tried to illustrate where those wires were/are below.
Not really part of the 'fix' I know, more just maintenance I suppose.
So that's this one back to 100% working again.
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