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Pinball Rehab

pinball repair and restoration

Board Rework and Test

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Pad and Trace Repair
When it comes to pad and trace repair the two common solutions are copper foil or jumpers. Both methods are functionally equivalent and which one you select depends on the specific situation and how original you want the board to look. One other method I should mention, since I get asked about it a lot, is liquid trace or silver conductive epoxy. Other than a few specific situations, like repairing the glass on a DMD, I stay away from them. Both solutions add some resistance to the circuit, which can sometimes cause problems,...
 
 
Repairing WPC Dot Matrix Controller
Display problems are typically the result of failing DMD's, bad ribbon cables or connectors, a cable installed one pin off (or reversed) or the high voltage section of the Dot Matrix Controller (called DMC herafter). Once you have confirmed the problem is with the Dot Matrix board (either logic or high voltage) this article will assist you with the troubleshooting process. For informational purposes I will also address some common symptoms that indicate problems other than the DMC board. You can either test the board in the game or use a test fixture...
 
 
Building a WPC Test Fixture
As my Dad would say, there are several ways to skin a cat. So while this may not be the ultimate WPC test fixture, the design was limited by a couple of my personal objectives. First I didn't want to mess with a transformer, and secondly I did not want high voltage on the bench. While this design precludes the possibility of troubleshooting DMD's or the high voltage section of dot matrix controllers, I can live with that. Most DMD problems can't be fixed anyways, and the high voltage section of the dot...
 
 
Board Rework Standards
While it's not always feasible for a hobbyist to adhere to industry standards in regards to board rework, it is a good idea to understand those standards. Plus, in many cases its not any harder, or more expensive, to repair a board to the IPC standards. IPC (The Institute for Printed Circuits) is the generally accepted standard for printed circuit board rework. While their standards documents would cost several thousand dollars to purchase, there is an alternative. Circuit Medic has an online guidebook that covers all aspects of board repair and adheres...
 
 
Circuit Board Updates
While I'm not a huge proponent of upgrading circuit boards (in most cases I find very little benefit versus the risk of damaging the board), but there are a few updates that are definitely worth doing. WPC DCS On your DCS sound board remove C37 and C45. This will help dramatically with the sound quality. The difference on games like Demo Man is dramatic. Williams did the same modification on later WPC 95 AV boards. WPC Power Driver Board If you experience the flipper enable relay (on the power...
 
 
Micro-Blasting Circuit Boards
The two primary reasons for micro-abrasive blasting a pinball circuit board are to remove the green solder mask (commonly, but mistakenly, called the conformal coating) or clean-up oxidation (see Images 1 and 2). In the past this would have been done with chemicals, but due to regulatory and cost issues, micro-abrasive blasting has now become the standard solution. The problem with a mechanical approach is that ESD (electrostatic discharge) is created, which can damage board components. In production environments specifically designed micro-abrasive blasters are used that minimize ESD. Unfortunately with a price tag...
 
 
Electronic Component Substitution
Some of the electronic components for repairing pinball games are getting hard to find. This article provides information on using replacement parts when the original is not available. I have also listed some components where you can still purchase the original part, but it is best to upgrade to a beefier component. The following Stern document, Component Cross Reference, provides NTG, ECG and Radio Shack part numbers for commonly used components. These are not recommended replacements but direct replacements. In some cases, as noted below, a more robust solution is recommended. ...
 
 
WPC Board Versions
The purpose of this document is to provide info on all of the WPC board versions manufactured by Williams and used in Bally/Williams games. There are three generations of WPC boards: WPC-89, WPC-S (security) and WPC-95. The following versions are subsets of the WPC-89 family: WPC Alphanumeric, WPC Dot Matrix, WPC Fliptronics and WPC DCS. All boards within the WPC-95 generation are interchangeable. Some, but not all WPC-89 boards are interchangeable (details provided below). WPC-89 boards and WPC-95 boards are not interchangeable. The A-XXXXX numbers provided for boards in this article...
 
 
Testing WPC CPU on the Bench
With a little knowledge and equipment it's possible to test just about every circuit on a WPC-89, WPC-S or WPC-95 board on the bench. This article will walk you through setting up a simple test fixture and testing the CPU board. Keep in mind that replacing circuit board components requires advanced soldering skills and proper equipment. While this article is intended to cover all WPC era CPU boards (WPC-89, WPC-S and WPC-95), there may be some minor differences between generations. For example, position of the component/connector on the board or different...
 
 
Repairing Plated Through-Holes
It is not uncommon to find damaged plated through-holes when repairing a pinball circuit board. There are two techniques commonly used to repair this type of damage: solder stitch or eyelets. First we'll look at analyzing the damage and then review the repair options. Analyzing the Damage Image 1 provides a side view of the plated through-hole. The through-hole is actually one physical part and the board trace a second physical part. They are electrically connected once the board is wave-soldered. It is fairly common for the connection to break right...
 
 
 
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