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Troubleshooting linear power supplies:

Is about the simplest job out there... possible testing light bulbs
in a lamp is easier, but the technique is still the same.

Start with your symptom:

If it is *no* power on any output, go to the other end, where the power
comes in, and work your way across until you find something that isn't
right:

1) power mains good?
2) power getting into box?
3) power getting past fuse and switch?
4) power getting to transformer?
5) power getting out of transformer?
6) power getting through bridge rectifier?
7) power getting to filter capacitors?
8) power getting to regulator
9) power getting out of regulator
10 power getting to output terminals

If there is correct power on some outputs, and incorrect output on others,
work from the output that is bad until you find good power.

1) power getting to inside of terminals?
2) power getting out of regulator?
3) power getting into regulator?
4) power getting to filter capacitors?
5) power getting to bridge rectifier?

That is all troubleshooting linear supplies is.

You don't need anywhere as much hand holding as you think you do.

As to exact voltages, that is rarely beneficial. You need to understand
ranges of voltages that are appropriate to the device you are looking at.

If the supply should be putting out 15V, then you expect 15V out of the supply,
and somewhere between 2 and 10 V going into the regulator.

Transistors never have more than 1V base to emitter in the direction the arrow
points on the emitter, or they are bad.. and current goes from + to - . In
the opposite direction, the transistor is off, and dead if it is above about
6 volts (reversed).

OPAMPS that have negative feedback (most) must have zero volts between the
"+" and "-" input, or their outputs will be stuck on a power rail... or they
are broken.

Power supplies are made up of a few dozen little jobs each like checking a
light bulb.

-Chuck Harris


daven9ooq via Groups.Io wrote: