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Before doing any work on the MPU, Make sure the MPU itself is getting +5.0 volts from the power supply. Cheers, - Sylvain.

Yes, the coil resistance for a 25-950 should be around 6.5 ohms. Have you replaced the diode across the coil lugs yet ? Also - Is the coil running hot after a while even if not activated ? Is the pre-driver transistor in the chip (CA3081) and associated 120 ohms resistor good ? (in addition to...

Re: What would cause a fuse to blow every 100 or so startups 1st thing I would check - make sure that the voltage arriving on the MPU (from the power supply) is +5.0-5.1 volts. Adjust the pot on the power supply regulator heatsink if needed. Also check for any possible cold solder joints under...

If you will be using Cointaker LEDs for pinball 6.3V bulbs applications, then it is simple and you do not need to worry about a series dropping resistor, as each LED assembly already has its own internal series resistor built-in. Simply provide a 4 x 1.5V battery holder for a total of 6V...

Is the transistor opening or shorting after these 10-20 operations ? Sometimes the diode on the Solenoid Driver board, driving the base of the drive transistor, can go intermittent. Also make sure the coil is the proper number (not an incorrect replacement), and measure its resistance to make...

Well, it looks like your house had a surge, not only a brownout. The red disk, a varistor, did its job, and shorted to protect the machine from a high voltage spike/surge. That will also blow the fuse next to it. If you are lucky, you will only need to replace that red burned varistor and the...

22 AWG gauge is plenty big enough for this application. You would need a bigger wire size for higher current applications, not for LEDs. Depending on the LEDs/types, typical current draw need is only 10-30 mA (e.g. 0.01 to 0.03A). If you wire them in series the current across all will be the...

Thanks all. The technical reason for this is the following: - when the fuse blows due to the too high current through it for its rating (e.g. the fuse blows for protecting the circuit as intended), the fuse element inside the glass has to open with a gap wide enough to *stop* the current flow...

Get the 250 volts type. For fuse replacements, you need to use the same current and speed as the original one (10A, fast or slow blow depending on the circuit), but you always can go higher in voltage, not lower - e.g. OK to replace a 32V by a 125 or 250 volt one. - Sylvain.

First, check the supply voltages arriving on the DMD board, and connectors leaving the power supply. Often the issue is with high voltage regulation parts on the power supply (diodes, transistors, resistors, caps). Good luck ! - Sylvain.

How's the AC ripple in the +15V supply going into the regulator ? Perhaps the main filter cap in the cabinet is bad. Or, bad pins in the connector to the +5V regulator board ? Cheers, - Sylvain.

Re: Gottlieb system 80B 5v power supply. Also check for cold/cracked solder joints at header pins, seen quite a few on those boards in the past. - Sylvain.

Re: F-14 tomcat. Right sling locks on at power up 1- make sure the right sling coil has its diode in place across the lugs, and is properly soldered. A missing or opened diode there would cause the Q71 TIP122 transistor to short after the 1st impulse. (if the diode was backwards or...

Coils usually do not short internally unless overheated or burned. Are you sure the wiring is correct to the lugs ? Are there two diodes on these flipper coils ? If so, check and replace the diode across the weak coil. That diode might be shorted - might occur after heating the lugs for too...