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Video Game Repair/video poker machine


I recently picked up a konami video poker machine and when I turn it on a message code comes up
MCU2 U21 back up ram failed any ideas would help

Gday Count,

Since our other Expert, Brian, does not do video poker machines he shot it over to the question pool.  So I give it a shot.

Fairly simple error message stating one of your chips on your board has failed or at least failed to read.  The MCU2 is probably the Microcontroller (maybe the second, MCU2) reporting a problem with ram, U21 I would guess would be the Chip identification.

Now this could be for a number of reasons.  Could be a damaged, bad RAM chip broken or damaged traces to the chip, or it could be a bad battery not keeping the RAM alive so it is corrupting the data on it or loosing it thus not reading it on bootup.

You might be able to bypass it by resetting.  But once the machine is off it goes back to the error.

Things to check.  See if the board has numbers or identification on it so you can see which chip it is.  Sometime the board is labeled A-Z on one side and 1-?? on another which would give you a grid reference to where the chip is or sometimes numbered next to the chip.  If the chip is socked-ed you could remove and re-seat.  If it has several of the same RAM socket-ed you could move a couple around and see if the error follows the RAM (Bad RAM) or stays in the same location. (Problem with PCB Board or traces)  If not check socked but directly soldered in place see if there is any damage to the traces going to it or if the solder needs to be re-flowed.

Check if the PCB has a battery on it.  Either a button battery or maybe a lithium battery soldered on it (May look like a big capacitor)  Test with a multimeter and see if it has the correct voltage, if not replace it.

Hope this helps.


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I can answer questions on Arcade or Home Console repair or modification.


Repair, rewire, modification, rebuild, restore. (I repair numerous business and private arcade/pinball machines in my area of the state. I partner with a shop that stocks older console based systems and games, I am the one that repairs them back to working order.)

Have been building, customizing and repairing all types of arcade games since 2004. I have been repairing and modifying video games since the late 80's. (Most of my knowledge is self learnt and following others that have trailblazed in the industry.)

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