Wow. I really wanted to stay out of this thread but there's too much mis-information that needs to be called out.
WPC has TWO "12V" voltage supplies. They are distinct. They are different. Please, please, please ... do NOT confuse them.
UNREGULATED 12V (known in the schematic as "+12 V POWER" visible at LED7 and measured at TP1 but hereby known as +12VU) originates from a transformer secondary winding at J112-1,2 and J112-3,5. It is rectified (BR5), smoothed (C30) and leaves the board at J116-2, J117-2 and J118-2. It leaves as a GRY-YEL wire.
REGULATED 12V (known in the schematic as "+12 V DIGITAL" visible at LED1 and measured at TP3 but hereby known as +12VR) originates from a transformer secondary winding at J101-4,5 and J101-6,7. It is rectified (BR1), smoothed (C6 and C7), voltage dropped (D1 and D2), regulated (Q2) and leaves the board at J114-1,2. It leaves as a GRY-GRN wire.
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+12VR is ONLY used by the switch matrix and Fliptronic comparators (LM339).
+12VU is used everywhere else ... including by the DMD or ColorDMD.
The Kahr boards takes the +12VR supply as the source for its regulation to +5VR. It does NOT take the +12VU supply as the source. You can load up the +12VU supply (to the point of overload) but it should not directly affect the +12VR supply. They are separate supplies from separate transformer secondary windings.
If a Kahr board is installed and resets suddenly appear you probably have a compromised Q2 (L7812CV or LM7812) regulator or a failed (potentially leaked) C2. The load for switch matrix comparison is VERY low. Once you put the CPU digital logic load it can cause a partially failed regulator to not be able to deliver the require current to maintain the required voltage. When the voltage falls below the watchdog threshold the system resets.
Using a Kahr board is NOT "free". It will cost you something. Often it will shift potential failure points to a location not recognized by a technician versed in WPC power design. It will cause confusion unless it is clearly stated that the Kahr board is being used and, of course, the technician needs to know what a Kahr board is. Even after that it will cause confusion ... witness this thread.
There's no such thing as a free lunch when it comes to power and failure. Just be aware of the trade-offs. Caveat emptor.
