[Amps] Strange power supply

[Will Matney]

Peter,

Correct, it don't take that long to check them all. To check those silicon alley diodes though, I don't think a regular ohm meter will do it since they're actually several diodes in series, and the meter is probably about 1 to 1.5 volts out on the ohms function. He'll most likely have to use a power supply, etc. to get enough voltage to bias the string into conduction in order to read whether they're good or bad. That's the way we used to have to check the old focus rectifiers, and damper diodes in TV sets.

I was working on a mobile amp once which the manufacturer had placed two holes on each side of the cover for mounting screws. The guy mounted it with a bracket under his dashboard and it quit working. I took the cover off and lifted the double sided PC board to find that one of the mounting screws cut a trace in two where the holes were too close to the board. The mounting holes came out between the bottom of the board and the heat sink. Talk about a design defect!

Best,

Will

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On 4/20/06 at 6:34 PM Peter Chadwick wrote:

>Will,
>>I just can't see a rectifier going open just setting.<
>You have more faith in semiconductors than I have retained after being in
>the industry for the last 27 years! Interestingly, over that period, I
>have had more semiconductor failures in my equipment than tube failures -
>and some of those tubes are actually more than 60 years old.
>Movement of the supply could be enough if there is a dodgy connection.
>Still, either which way, none of it's too hard to check. These days, I
>have to build all my stuff so that it's inaccessible to the cats. Doesn't
>stop them trying to poke their noses in! I think their excuse is 'taking
>an intelligent interest in the environment' - I call it 'poking fat noses
>in where they don't belong'.
>73
>Peter G3RZP 
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