This is the VHF version of the Motorola MSF-5000 repeater, Model C63CXB7106BT. What started out to be a fairly simple project, turned into a nightmare. Simple programming should have been all there is to it, but that's not what happened. After three days of burning in the unit, something began shorting, drawing 15 amps, AC. Strangely enough, it only happened in the morning. All worked fine in the afternoon. The difference? Temperature. When it was cold, it shorted. When it warmed up, it was perfect. Power supply? The difference in temperature was only about 15 degrees. So here it is and we'll go into the problem further down.
The MSF has alarms that are transmitted when something goes wrong. While this short was happening, four beeps sounded, indicating battery over voltage.
After naming the power supply suspect, it turned out that the problem was the battery charging board. An unknown component on the board was shorting when cool, but behaved correctly when warm. As luck usually does not have it, the exact Motorola P/N was offered NOS on Ebay. The entire board for $20 and free shipping. The board was installed and all the problems went away.
You would think all is good to go, but the unthinkable happened. I walked into the shop and flames were coming out of the cabinet air vents. It caught fire, destroying most of the power supply. It was so hot it melted a hole in the aluminum cover plate on the PA. Power was disconnected and the fire was extinguished with a bottle of Windex.
The upper left capacitor exploded and caught fire. Being a determined tech, I replaced the cap and rewired the PS. It's working once again, I hope.
Don't ever think this could never happen to you. Capacitors are time bombs. They can go at any given moment. Luckily, I caught this one before the worse happened.
