The term "rebuilt" originally came into use in the petroleum equipment industry when equipment was 100% mechanical. The term correctly describes the disassembly and renewal of meters, pumping units, and computers. As applied to electronic boards, however, it is really not accurate. For boards, the "rebuilding" process is really one of testing and repair.

How does board reliability work?

Before we talk specifically about "rebuilding" boards, it’s important to understand the nature of electronic systems reliability. Basically, the in-service reliability of a well-designed system is determined almost completely by the number of interconnections between its elements. The term "interconnections" includes the wiring between a circuit chip or transistor and its package, the soldered connection between the package and the circuit board, and all the individual conductors in separable connectors within the system. Even a simple system like a gas pump has thousands of interconnections. To a lesser extent, the reliability of the system is determined by the type of interconnections. Solder joints and circuit wire bonds, for example, are more reliable than separable connections made via cable plugs or board-edge connectors.

To state this another way, the majority of electronic system failures are not failures of circuits or components. They are failures in connections. Vibration (i.e., shipping), moisture, and temperature changes (hot/cold cycling) are the cause of most of these connection failures.

Component failures do occur, often due to design errors or environmental stress (overheating, for example), but in general a component that has functioned through its initial placement into service (i.e., "burn-in") will function reliably for many, many years.

So what does this mean to someone who repairs gas pumps?

The first thing it means is that "bad" boards are much less common than you think. Board rebuilders expect that 30% or more of the boards that come in for repair are, in fact, perfectly good when they arrive. Pump technicians have removed these "bad" boards and installed replacements – where the real repair was to plug and unplug a board to clear up the bad connection that was keeping the pump from working. The board gets blamed, then falls into the "already-good" category when it arrives at the rebuilder. It also means that you can save a significant amount of money by re-testing boards before sending them in for rebuilding. After fixing a problem by changing one or more boards, a pump technician should always try re-installing the original board(s) to see whether the problem reappears or not. If it does not, there is a high probability that the problem was not internal to the "bad" board.

What does "board rebuilding" mean ?

It really means "testing and repair." In a typical rebuilder’s flow, the boards are received and cleaned. Then, they are upgraded to current "E.C.O." (Engineering Change Order) status with software, component, and/or wiring changes. In some cases, a board will have a particular component that is known to be weak. The weak component might be changed at this point as well. Following cleaning and automatic upgrades, something like 40% of boards will usually test "good." These are simply marked, packaged and put into finished goods inventory.

Boards that test "bad" then go through a trouble-shooting and repair process before being marked and packaged as finished goods.

It’s important to understand that this process, unlike mechanical component rebuilding, never includes extensive disassembly and changing of components that are not specifically determined to be bad. In the world of electronics, such wholesale changing would cause major degradation in the board’s reliability due to upsetting connections and installation of unproven components. In addition, it would be prohibitively expensive.

Display Boards: A Special Case

Gas pump price display boards are the exception to two of the general statements made above. First, the display components themselves are quite subject to failure that is unrelated to interconnections. Second, most board rebuilders will change all display elements on a board, not just the bad ones, when a display board is rebuilt.

What’s the bottom line?

1) When trouble shooting, expect that the problem will be connection-related. This can save you equipment downtime and enable you to solve a problem where you may not have a replacement board on hand.

2) Retest boards, except for displays, before sending them for rebuilding. This will save you a money on board costs.

3) Don’t think that boards are rebuilt in the same manner as mechanical components. Realize that it is a repair process that is the best means to minimize cost and maximize reliability.

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