You will need a DMM (Digital Multimeter) to perform these tests. They are fairly inexpensive and could be bought for 40$ or 50$ or even less if on sale, for a decent one. You want it to have a diode setting, AUDIBLE signal for continuity (much easier on you and much more convenient, it emits a sound), AC and DC voltage, DC Current, Ohms settings. Anything else on it is fine and an added bonus, but capabilities above are what you will be measuring the most.

Fluke brand multimeters are the kings of them all, they are the Lamborghini of multimeters. But, in case of pinball machines that much reliability and power is simply not needed in most cases. Any multimeter, even crappy Made in China will do provided it has the settings most commonly used.

Even though Flukes are simply the best on the market money can buy, they are much more expensive (200$-300$ - you have to pay for quality!) for a casual user that uses this device very infrequently. Therefore, any multimeter will really do. Even Radio Shack sells decent ones. Again, you want a multimeter that has diode checker, DC voltage, AC Voltage, DC Current, Ohm settings (it will either say Ohms or have a Greek Omega sign) and audible continuity (much easier when testing). With these settings you can pretty much test and measure most parts in a pinball machine.

If your transistor is dead, shorted or open it will need to be replaced. You will need a soldering pencil (not your dad's old soldering gun). I cannot teach you how to solder and it's beyond scope of this simple page (in one of the other refurbishing tips we are showing how to solder/desolder). Experience and practice are the best teachers.

IMPORTANT! Please use due care, common sense and a lot of precaution while using this advice and I will not be held accountable for use/misuse/abuse or for any other way for you to mess something up. If you're electronically challenged, please do not use this advice at all and please do not try to friggin' measure, poke around, "diagnose" and/or replace anything at all.

If you suspect that your machine has faulty components, please seek advice from a qualified pinball rapairman to look at it and fix it properly.

Here is the big WPC Power Driver board we'll be testing a transistor on. It is the main board that all the transistors for solenoids, flashers and lamps are.

If a transistor is found faulty, it will need to be replaced and a new one soldered onto the board, then tested and retested for continuity. We'd be using a quality soldering station for that. The temperature showing on the station (more than 800F) is very likely too much. Around 700 - 720 Fahrenheit works best. Also remember that every TIP102 driver transistor has a predriver transistor that will need to be tested and replaced too. Consult your manual and schematics.

One of our digital multimeters getting ready to be used.

Set your multimeter on DIODE setting as pictured. On this particular model diode and continuity setting with audible signal are on the same spot. Sometimes they are separate.

Most transistors used for pinball machines are TIP102, TIP107, TIP36C, TIP122 and TIP140. NTE makes all of them are they should be readily available off the shelf at any electronics store. There are 3 legs on a transistor and all 3 are soldered onto the board. Put the BLACK lead of your multimeter to a middle leg or a hole on the top of transistor which acts as a middle leg. For TIP36C, put the RED lead in the middle and BLACK lead on the outside legs.

Put RED lead of your multimeter to the outside transistor. A reading of between 400 to 600 should be seen (+ or minus 10% is acceptable). Anything much higher than that or lower than that means the transistor is fried and will need to be replaced. So, if you get "387" or "613", that's fine, it's within specs. Do the same for the other side and confirm readings.

Let's test a resistor while we're at it, for the hell of it. Put your DMM to Ohms setting like shown.

Look into your manual, find the resistor in question and see what it's value is supposed to be then confirm the finding with a multimeter readout. you can also determine resistor's value by the number and color of its stripes.

With setting on Ohms, put the leads on either side of the resistor. The readout will be on the display. Account for +/- 10% tolerance and compare with the finding.

First ignore the cool coffee mug stains next to a multimeter. It comes from a lack of sleep, just focus on the friggin' meter. Remember if the supposed value of the resistor in question is higher than the Ohm setting you have your multimeter on, it will show Out Of Range (some multimeter will show OL - Over Load reading), and you might (falsely) assume it's bad. Simply increase the setting on the multimeter wheel and try again to confirm it in the good (higher) range.

Multimeter testing is fun. That's it for now... To be continued...

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