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Gottlieb LM338 fail

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bones View Drop Down
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    Posted: 12 Dec 2022 at 6:12pm
    Hi, a gottlieb street fighter 2 pinball has had an LM338 regulator fail. The problem is that it has gone closed circuit meaning that 12v has been sent everywhere that the 5v goes. Unfortunately gottlieb apparently chose not to put any protection against this for the first time on this generation of machines, they did again after unsurprisingly.
    What sort of damage am I looking at here? Does this mean that all the chips on all the PCBs are fried?
    If it is a worst case scenario would a complete set of new PCBs even be viable bearing in mind the pinball is probably only worth £2000 fully working (seen a couple of much higher prices but Liberty games are way off the mark compared to actual sold units)
    If you do own a pinball of this generation it has been recommended elsewhere to remove the small PCB with the LM338 on it and install a normal arcade switch mode PSU using only the 5v to power the machines 5v through the old PCBs output plug instead.
I need a chip marked C104 for a century electronics Hunchback PCB or a donor board with one on. Thought I'd got one sorted but it never materialised unfortunately
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cliff_poole Quote  Post ReplyReply Direct Link To This Post Posted: 12 Dec 2022 at 8:25pm
I had a similar thing happen on a Williams Pinbot. It wasn't powered on for very long with the higher voltage. Luckily, in my case, all it did was corrupt the data in the EPROMs so I was able to erase and re-program them.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bones Quote  Post ReplyReply Direct Link To This Post Posted: 13 Dec 2022 at 5:18pm
    I will try powering a separate 5v to it but being gottlieb there doesn't appear to be any ROM sets to compare against. I read that someone bought the rights to these hence why they don't appear on any 'free' sites. I'm assuming my only hope would be to find some kind soul who owns this machine and can download and email the files.
I need a chip marked C104 for a century electronics Hunchback PCB or a donor board with one on. Thought I'd got one sorted but it never materialised unfortunately
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ArcadePCB Quote  Post ReplyReply Direct Link To This Post Posted: 13 Dec 2022 at 10:58pm
I would try to power it up using an adjustable power supply with an adjustable current limitation. Set it to 5V and the current limit not too high. If there is no extremely high current, there's a chance not too much was damaged. If the current is way too high (or the voltage is much below 5V at a suitable current), try to find out which components are becoming hot. Remove them and try it again, until the current consumption is in an acceptable range. Then replace the removed components by new ones (use of good sockets for removed parts (IC's) highly recommended).
That's the way I would start.
But be aware, overvoltage is the worst case (wrong polarity as well, of course). It's possible almost everything is fried now, if you didn't have much luck. And even if not everything is destroyed, the components still working now may have been damaged anyway and will fail soon. You can just try it, hopefully you're lucky and almost nothing's destroyed.
I wish you the best.

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