Midnight Resistance Repair Log #4

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Womble
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Midnight Resistance Repair Log #4

Post by Womble »

Yup another one, I now have far too many Mid Res boards ;)

I promise this is the last Midnight Resistance repair log for a while, I have no idea why so many faulty ones have popped up over the last few months, haven't seen any workers for sale anywhere.

Anyway - this board was mint, absobloodylutely mint, could have been made yesterday, not a scratch on it. The only thing I could see that worried me was 2 blacked pins on one of the custom LB0072 custom chips...

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...this is a sure sign that something dropped on the board while it was running and shorted these pins out, OR more likely, someone trying to fix the problem jammed their probe between the two pins. When this happens its really a case of luck as to how much damage you can do. If someone is stumbling around probing stuff and they bridge two data pins then this wouldn't do much but if one of those pins was +5V and the bridge gave that a nice easy path to ground then the PSU will gladly step up to the challenge and supply all 15Amps of current at its disposal along that path, until something nominates itself as the fuse and burns out, usually instantly with a puff of smoke and a bad smell, incidentally if you do manage this (we have all done it once or twice) its always useful to postpone panicking or swearing and take notice of where the smoke came from, often a track on the board will have gone from stone cold to red hot and vaporised in a fraction of a second, the burnt out gap can be tiny and hard to spot, so follow the smoke!!! The burnt out section is not likely to be the only fault but at least if you know where you buggered it you can fix it and move on, if you have no idea where it was then its going to be a struggle.

Anyway I had a feeling that the custom was toast and was preparing to have a go at replacing a 160 pin surface mount chip as I have another Data East board as scrap with these ICs on it.

The game booted ok, but some of the gfx were not right.

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The in game looks OK but the backgrounds are missing a lot of the colours other than green even tho it actually looks pretty good! Not overly surprising seeing as these LB0072 customs control banks of graphics EPROMs ( I worked out its pinout from a couple of schematics of other games - should doco it for here ).

First step when troubleshooting graphics issues is to check the ROMs, usually they are socketed and its quick and easy, even if it is a bit boring on boards with lots of ROMs. The gfx roms on this board were all mask ROMs, is ROMs that were made with the data already in them, etched in with a photo resist mask that defines the internal structure which defines the data. The were all TC541001P chips, which my reader didn't support, however they are pin for pin compatible with 27C100 EPROMs odd pinout really) so it kinda did support them. Anyway - they all dumped fine except for ROM 9 and ROM 11, both showed up as having blown address pins, #9 was missing 2 pins and #11 was missing 9. Both were ROMs associated with the suspect custom chip.

So I did a check on the board to see if there were any shorts to either ground or 5V on any of the ROM pins, (to make sure the board wasn't going to destroy any chips put into these sockets) burnt new copies of #9 and #11 into a couple of AM27C100 chips using the data from the MAME set, dropped the chips in

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and fired her up....fixed!

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Am lucky that custom wasn't bad considering the violence it was subject to, surface mount customs are generally very hardy beasts anyway thankfully. Plus it would have been a shame to have to scuff up such a mint board tho I admit I was up for a go.

Right that's my last MidRes board, seriously I don't have any more ;)
Last edited by Womble on February 11th, 2010, 1:19 am, edited 1 time in total.
dreadzone
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Re: Midnight Resistance Repair Log #4

Post by dreadzone »

Your repair logs are so interesting. It's really a pleasure to read and learn from them.

Thank you very much for your work. :thumbup:

DZ
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Devil Soundwave
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Re: Midnight Resistance Repair Log #4

Post by Devil Soundwave »

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ROBO84
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Re: Midnight Resistance Repair Log #4

Post by ROBO84 »

Yep, another good read, well done for all the repairs and taking the time to document it all.
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Re: Midnight Resistance Repair Log #4

Post by gargoyle67 »

Hell yeah don't worry about how many of the same board you document each repair seem to be different and interesting, I wait for your next cool doc 8-)
"Yeah lets all get ponys instead, wait no lol trendy cabs" Err I think you meant Ponies didn't you ?
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Re: Midnight Resistance Repair Log #4

Post by geotrig »

:thumbup: :thumbup: great stuff as said there great to read ,they even make me think i could fix a board!!
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<trk>:I remember catching a big fat one and my friend said "throw it back in, that one already tastes like wood"
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Re: Midnight Resistance Repair Log #4

Post by Devil Soundwave »

geotrig wrote:they even make me think i could fix a board!!
Agreed - the tone of these logs that Womble has been posting has convinced me to have a go so I've bought a load of test equipment. :)
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Re: Midnight Resistance Repair Log #4

Post by Womble »

Awesome!!! Let us know how you get on, any questions just drop me a PM.
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Re: Midnight Resistance Repair Log #4

Post by Devil Soundwave »

Womble wrote:Awesome!!! Let us know how you get on, any questions just drop me a PM.
Just building a little test rig and should be good to start. Ny bew Oscilloscoope is awesome (Tektronix 465b)!
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Re: Midnight Resistance Repair Log #4

Post by geotrig »

Devil Soundwave wrote:
Womble wrote:Awesome!!! Let us know how you get on, any questions just drop me a PM.
Just building a little test rig and should be good to start. Ny bew Oscilloscoope is awesome (Tektronix 465b)!
fair play to you mate,if it was me i'de buy all the stuff then realise i have a clue what to do even after reading all the good repair logs!! :awe:
make sure to make a log of your first attempted repair !
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<trk>:I remember catching a big fat one and my friend said "throw it back in, that one already tastes like wood"
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Re: Midnight Resistance Repair Log #4

Post by roeckerj »

I just bought my first few arcade games at a video game auction and a couple of them have issues that I would like to see if I can repair myself. First, Midnight Resistance, by Data East, is an awesome game, but the screen will start flicking and go out after it has been on a while and even restart when playing it. The screen is somewhat faded as well. I am thinking maybe it is a fuse that is overheating or that the screen is just going out.

Second, Point Blank 2, by Namco, looks fun but one of the guns did not work. You can feel it shoot in your hand but it does not transfer to the screen. I tried going through the options screen to turn it on but it would not stay on, reverting back to the gun being off. I accidentally turned the working gun off as well. Please help if you can. My kids love the games but they are kind of hard to play in their current condition. This is my first time to try to post something like this on a blog. I can be reached via email at jarrodroecker@gmail.com.

Please help and thanks to anyone out there who does!
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Re: Midnight Resistance Repair Log #4

Post by Womble »

roeckerj wrote:I just bought my first few arcade games at a video game auction and a couple of them have issues that I would like to see if I can repair myself. First, Midnight Resistance, by Data East, is an awesome game, but the screen will start flicking and go out after it has been on a while and even restart when playing it. The screen is somewhat faded as well. I am thinking maybe it is a fuse that is overheating or that the screen is just going out.
Hmm, well it sounds like you have a monitor chassis fault not a PCB issue, am afraid your comment about the possibility of it being an "overheating fuse" is really telling that you don't know the first thing about how monitors work, not trying to be an @rsehole here but you may also underestimate how dangerous they are if you don't know what you are doing. Even when powered off they can still give you a very nasty shock, and when on they are literally lethal in places, tens of thousands of volts with plenty of amps to back it up. Your kids may love the games but I am sure they would prefer you didn't kill yourself trying to fix it. Its possible that a cap kit would fix the issues but its also possible you have dry joints somewhere, either way you would be poking around the dangerous areas to try to isolate it. There are people who have the tools to fix these things safely and its worth paying them the money to do so, its not that expensive, they really are not serviceable by a novice.
Second, Point Blank 2, by Namco, looks fun but one of the guns did not work. You can feel it shoot in your hand but it does not transfer to the screen. I tried going through the options screen to turn it on but it would not stay on, reverting back to the gun being off. I accidentally turned the working gun off as well. Please help if you can. My kids love the games but they are kind of hard to play in their current condition.
Its possible the wiring is broken between the gun and the PCB, you will need to buzz through the wiring in this section, the PCB side of things is quite safe to work on. Sorry to put a downer on things but people are killed messing about with monitors and TVs, it really isn't worth trying to save money by trying to fixing them yourself.
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Re: Midnight Resistance Repair Log #4

Post by gargoyle67 »

I fixed my monitor myself and I'm a novice :awe: I did discharge my tube though and steer clear of the flyback transformer, It was only a dry joint on mine so I just "blitz" the chassis with new solder neckboard also. Womble is right though if your not competent you should not attempt it.
"Yeah lets all get ponys instead, wait no lol trendy cabs" Err I think you meant Ponies didn't you ?
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