I could use some help on finding a replacement Transistor. One of the depth finders on our boat has failed and shows a dead short on the power input lines. The problem may be a shorted Transistor in the power supply section. I haven't removed it yet because i wasn't sure i could get a replacement. It has a Motorola logo on it and the numbers 734 and J31. It is a SOT23(?) surface mount package.
My Internet searches couldn't find the Mot part, but found a FMMT734. I'm not sure that is the correct match. Can anyone give me some information this component and where i might be able to purchase one?
Best Answer
It's an MJD31, which is equivalent to a TIP31 (a popular 3A 40V NPN transistor).
To see if it is causing the short you could just unsolder the Emitter lead. Inductor L3 looks like its insulation has broken down, and will also need to be replaced or rewound.