The Aussie Pinball Arcade
Aussie Pinball Forums => Technical Matters => Pinball Repairs / Problems & Assistance => Topic started by: aurum on June 18, 2018, 08:03:20 PM
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Hi all,
I've got a Monster Bash pinball that's been in storage and upon powering up I had an initial error of 4 beep - indicating error in rom S4.
I removed the board and re-seated all roms and metered the roms and got all pins connected except the enable pin (22) - as expected.
I put the board back making sure all connections were correct and I now get 1 and a bit beeps. It's as though the processor is being reset about a quarter of the way through the second beep.
Anyone any ideas or suggestions?
Edit, could this be the WDT kicking the dog?
Mike.
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Some progress (if you can call it that). after doing absolutely nothing except leaving it overnight the error has changed to 4 beeps indicating an error in sound rom 4. The rom is seated correctly and meters ok pin for pin with the other roms (bar the /E pin).
I'm wondering if during storage some damp has somehow caused problems. Has anyone come across this before? I'm going to leave it powered up for the rest of today to let it warm through and see if that helps.
If it turns out that rom4 has gone belly up, where can I obtain a rom image so I can burn a new one?
Mike.
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I think I've found the problem. Although the batteries were removed a long time ago, it looks like the alkali wasn't neutralised.
The socket in the attached photo is for the 6809.
I plan to remove the socket and repair any tracks before replacing with a new socket.
Any hints and tips or things to avoid etc.
Mike.
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A little more progress - socket removed. I'd forgotten how easy it was to desolder these old through hole boards - everything these says is smd and the tracks are thous wide. Think I'll leave the track checking until tomorrow.
Any hints and tips are still very welcome.
Mike.
Edit, the errors I was getting started becoming more and more random. I figured bad connection somewhere and then spotted the damage. Hopefully restoring the PCB to working order should sort it out. will keep you all posted.
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Check out this youtube video. Looks similar to yours. This guy does some good work. If you don't get rid of all the corrosion it can come back on you.
https://www.youtube.com/watch?v=ey5e5ssnvfs (https://www.youtube.com/watch?v=ey5e5ssnvfs)
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Thanks for that. It has confirmed what I suspected, I need to remove all the components with corrosion under them. The nice thing is that these boards are much more rugged than any modern board so easier to desolder. Plus, only two sided which makes it much easier to follow tracks etc.
Mike.
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Also neutralise the affected parts with vinegar as you go.
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Also check the ASIC socket. You will have to remove the chip.
Once you have the board working, consider NVRAM or mounting batteries externally.
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After removing a few more components and an initial clean reveals many eaten away tracks. Think I'm just going to use wirewrap on the back of the board as a means of repair.
Mike.
Edit, any suggestions on what to coat the bare copper with?
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https://www.jaycar.com.au/circuit-board-lacquer-spray-can/p/NA1002 (https://www.jaycar.com.au/circuit-board-lacquer-spray-can/p/NA1002)
You can use this to cover the tracks. It looks like it needs a bit more sanding with a very fine grit to get as much shine back in the copper as possible. If you sand through a track you can put a jumper in.
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https://www.jaycar.com.au/circuit-board-lacquer-spray-can/p/NA1002 (https://www.jaycar.com.au/circuit-board-lacquer-spray-can/p/NA1002)
You can use this to cover the tracks. It looks like it needs a bit more sanding with a very fine grit to get as much shine back in the copper as possible. If you sand through a track you can put a jumper in.
+1
Use Isophrophyl alcohol to clean the area after your work is done - before using the lacquer.
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Corrosion is a bitch and would have gone beyond what is visible on the PCB... best of luck!
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I've now cleaned the corrosion, replace the 6809 socket and socketed the 7414 and replaced the parts around it. I then put it back in the machine. It booted and reported it had done factory reset (no batteries so no surprise there). After 30 seconds it started resetting repeatedly and then died. I've now got a dead CPU board even though I am sure that everything was correct. Guess I'll leave it until tomorrow now as I'll have to rig up a bench supply for it. Does anyone know if just supplying 5V will allow the processor to run?
Mike.
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Success, kind of. I reseated the PLCC chip and now it boots periodically. The chip and socket are both corroded. I've ordered a new socket of ebay but it'll probably take 6 weeks to arrive. Anyone know of a source in Brisbane for these (PLCC84 through hole) sockets? In the meantime I'm going to try a can of contact cleaner from Jaycar.
Mike.
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This do you?
https://au.rs-online.com/web/c/connectors/ic-sockets/plcc-sockets/?searchTerm=plcc%20socket
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That'll do it. Thanks.
Think I'll leave the unsoldering of the PLCC until next week, done too much already this week.
Mike.
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The PLCC100 (not 84 as I earlier thought) socket finally arrived and after much solder sucking the board is ready to accept the new one.
New socket soldered in and success - all working again.
A word of warning for anyone attempting this, the asic can go in the wrong way around - luckily I checked before powering up - the writing should be the right way up when in the machine.
I'm now considering using a 18650 battery with a battery conditioning and charging circuit as the battery backup. Anyone any thought on this? Fire risk?
Mike.
Edit, how do I remove the extra attachments? Every time I try I end up with more!!
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I may have spoken too soon !!! . It worked fine for about 3 hours and I've now got a dead CPU board. I now have the blanking LED(201) permanently on and the Diagnostic LED(203) permanently off. Think I'll wait until tomorrow to power it up on the bench and try and diagnose the problem. Anyone any pointers? Also, anyone know what current is taken from the 5V supply by the CPU board alone?
Mike.
BTW, the PLCC is 84 pins - don't know why I thought it was 100 earlier.
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Just powered it up on the bench and started to trace the blanking signal. Got half way through tracing it and it had the wrong polarity because the blanking LED had gone out and the diagnostic LED started flashing. Put it back in machine, worked for two minutes then back to dead.Back on bench, 30 seconds later working again!!! It's now back in the machine and appears to be working fine but I suspect there is a faulty connection somewhere. Time will tell.
Mike.
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Sounds to me like there may be more corrosion at play here. If there was no history of corrosion, I'd say that the issue could be the sockets - CPU, ROM and 6464, or the ASIC is loose. With the game on the bench, you need +5V but I always have +12V as I simply use an old PC AT power supply. With the CPU PCB on the test bench, see if you can get it to fail - push the ASIC in and the socketed chips until it locks up. If it does not, then it will be something on the driver board, or the ribbon cables.
Have you got another machine to swap out ribbon cables ?
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The error appears both on the bench and in the machine. The error first disappeared when I tried tracing the RST line as the 6809 was being held in reset. Whilst tracing this signal the board sprung into life. It then worked for a short time in the machine but at the next power cycle the error returned. As it was whilst checking around the 7414 that it came to life, I swapped that for a new one. I've now changed also the asic and the 6809 but the error persists. Once the board springs into life it continues working until the next power cycle. Tomorrow I'll try resoldering the whole board in case there's a hairline crack somewhere.
Mike.
Edit, why is this being posted with a tiny font size? Just had to up it to 12 to see it.
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Intermittent faults are painful but im assuming that when you tested the 7414 you were testing voltage or signal on the pins. If its in a socket, id be replacing that straight away. It only takes a nano second for the logic signal to drop out. Corrosion may have eaten into a few traces also and so a rub back and solder flow may be the way to go
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I've finally got around to looking at this again and simply went over all the replaced components and resoldered all the connections. So far, fingers crossed, it is all good again. I deliberately held the iron on longer than normal to allow the solder to melt all the way through the hole and that seems to have done the trick.
Mike.
Edit, late Friday here - time for a well earned beer.
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Good to hear! ^^^
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Hopefully it is all good from now on !
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All's been good for 3 days and many power cycles so hopefully the problem is solved. Just got to fix the up/down table for Frankie now.
Mike.