The PSU5 was designed to be a plug 'n play switching power supply that's able to
replace common linear voltage regulators such as the LM323K or 78H05. I've been
upgrading numerous power supplies with them; mostly WPC 89 Power Driver Boards
and a few arcade boards. Really impressed with their performance thus far.
A NBA Fastbreak was sitting in our shop and was next up on the list for
servicing. Since I've yet to install a PSU5 into a WPC 95 PDB, the exercise
seemed worthwhile. Lo and behold it didn't "just work" after installation.
Williams changed up the 5v regulation circuitry on the WPC 95 and opted to use
a LM317K linear adjustable voltage regulator. As someone that's used to fixing
previous generations of Williams games, this was a slight surprise and a
gentle reminder of paying closer attention to part numbers.
The LM317K has a pinout and function that differs from the LM323K. We'll need to
chop up the board and run some jumpers in order to utilize the PSU5.
LM323K Pinout: 1 - Vin, 2 - Vout, Case - GND
LM317K Pinout: 1 - Vadj, 2- Vin, Case - Vout
In the attached pictures, red denotes a trace cut, blue is a point-to-point jumper
and yellow is a tag for the component.
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First, we need to isolate Q1 (VReg)
On the parts side, cut the trace from the screw holes to C1's positive lead.
On the solder side, cut the following traces:
Q1 Pins 1 & 2
Q1 Top case nut to R2
Q1 Bottom case nut to SR1, Q6 (Both sides of the nut)
Q1 should be completely isolated from the board now.
Now for the jumpers:
C4 to Q1 Pin 1 (Old trace: C4 to Q1 Pin 2: +12v)
Q6 to Q1 Pin 2 (Old trace: Q6 to Q1 Case: +5v Out)
SR1 to C1 Positive Lead (Old trace: SR1 to Q1 Case: +5v Out)
C1 Positive Lead to Q1 Pin 2 (Old trace: component side Q1 Case: +5v Out)
C2 GND Lead to Q1 Case Nut (Not grounded previously)
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Now LED101 should light up, your game *should* boot, and you will have a more
reliable, less power hungry, and cooler running board!
Columbus, IN
