Power supply malfunction

[Megawatt]

What a MegaWatt you would have to have the MOSFET oscillation frequency run away out of control simultaneously with the failure of the overvoltage protection circuit. This would be incredibly rare and if it did happen could only produce 16 volts.

 

[kaos513]

Fuse should had blowen if it was that high

 

[Megawatt]

You would hope so. But lots of damage can happen just before it blows.

 

[Captain Kilowatt]

You would hope so. But lots of damage can happen just before it blows.

Indeed. As fast as we think a fuse blows it is actually a long time when talking about solid state switch times. I have seen many expensive transistors nobly sacrifice themselves to save a cheap fuse.

 

[Megawatt]

Yes, well said. Unfortunately fuses are designed to handle spikes, inrush current and motor start loads that can be double the value of the fuse.

 

[nomadradio]

A fuse prevents fires.

Protecting components from overload is a whole separate issue. Fuses are there to prevent a fire AFTER the expensive components have already failed.

After all, the final transistor won't draw sufficient current to trip a fuse until after the damage is done.

Not before.

73

 

[Megawatt]

That is very true.

 

[Jhawk]

That is very true.

Thank you nomad. I replaced the final and its working great. Now i have 2 other radios that it happened to i suspect the same thing.

 

[Shadetree Mechanic]

Interesting read, this has got me thinking. I have a Tripp Lite 12A supply that had a shorted crow bar transistor.... so I clipped it out. Looks like a Mega Watt supply is going to be the next thing I buy. lol