WPC MPU Power Fix PRO daughterboard – 2018 edition !!!

WPC MPU Power Fix PRO
Stop your WPC machine from resetting because of power supply issues!  This listing is for the WPC MPU Power Fix daughterboard
that I designed
(no, the MPU board is NOT included; it is merely shown to demonstrate installation).  This daughterboard is professionally made in a US-based PCB board shop and the components are soldered together in Virginia.
This listing is the 2018 Edition PRO version of the WPC Power Fix daughterboard with 2018 version of monitoring software installed.
What it does
This circuit creates a unique 5 volt power source for the MPU board separate from the rest of the machine.  Resets happen on WPC pinball machines because the Driver Board’s 5 volt power supply is minimally sized for the many functions it needs to drive.  WPC series MPU Boards have a watchdog circuit that shuts down the board if the voltage on the 5 volt line drops below a cutoff voltage (around 4.7 volts).  When this happens the machine appears to unexpectedly turn off – immediately ending any active games. Interestingly, the watchdog shutting down the MPU board often sufficiently reduces the draw on the 5 volt power supply such that the voltage quickly recovers and the machine starts booting as if all were well once again.  Unfortunately all is not well – in some cases re-energizing the MPU board just as quickly pulls down the 5 volt power supply and the watchdog again turns off the MPU – creating an endless on/off reset cycle about every few seconds.  Your machine may not currently enter this rapid “reset loop” but if your machine resets, your machine will experience additional resets – the periodicity of your reset loop may be minutes (or even an hour or more) but you are just waiting for the next reset.
The WPC MPU Power Fix daughterboard eliminates watchdog resets by moving the MPU load off the 5 volt line to the 12 volt line.  If you look at the WPC MPU Power Fix board, several pins are missing from the wire-side connector… this is because the Driver Board 5 volt line is no longer passed to the MPU.  Instead a switched regulator generates a very stable 5 volt supply that is used only on the MPU.  This reliably satisfies the watchdog circuit and therefore the MPU board is not reset.
The PRO version adds power supply monitoring functionality to the daughterboard – the 2018 Edition Pro can monitor both the 5 volt and 12 volt line on your PDB and has a simple LED indication scheme to inform you of the status.  Green means “every thing is good” (doesn’t Green always mean good?), flashing Green means 5 volt went too high.  Red means the 5 volt circuit is fluctuating to the point it
would have
caused a WPC reset if the daughterboard were not present, flashing Red means the 5 volt went very low.  Blue means the 12 volt circuit is fluctuating significantly (more than 3 volts).  Both Red and Blue mean both the 5 volt and the 12 volt are experiencing fluctuations.  NEW with the 2018 edition is a button that clears any LED error indications so the troubleshooter can restart the monitoring without power cycling the game.
Other parts of your pinball machine still use the original 5 volt power supply so best maintenance practices such as replacing failed capacitors, burnt connector pins, and non-functioning rectifier diodes still must be performed – especially if you are seeing the flashing Red indication.  At long last, however, you no longer have to worry about every hundredth of a volt when conducting these repairs.
Don’t miss the “Detailed Technical Discusion” at
www.kahr.us/index2.html
See It Work
Here is a short video showing the WPC MPU Power Fix solving resets in my Party Zone pinball: WPC MPU
Power Fix on YouTube
How to install it
The WPC MPU Power Fix circuit board is plug compatible with WPC, WPC-S and WPC95 MPU Boards.  You need about 1.25 inch of clearance above the MPU board to install the daughterboard.  Simply unplug the 7-pin power connector from your MPU.  Plug this connector into the WPC MPU Power Fix circuit and then plug the Power Fix daughterboard circuit into the MPU board.
The WPC MPU Power Fix daughterboard is designed and assembled in the United States by KAHR.US Circuits… a pretty small operation – just me in my spare time!