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Interleaved:

Thanks for all of the input so far!

As suggested I checked the low voltages for ripple with a multimeter and a scope.

Only the 110V and 15V rails showed significant ripple on the scope and only the 110V had AC on my multimeter.? I've added photos here:

Then those supplies are suspect.

/g/TekScopes2/album?id=278262

The 110V rail measures 104.9 VDC; the 15V rail measures 12.99V.? Using the multimeter the AC ripple voltage on the 110V measured 10.21V!? The scope appears to indicate 10.4V.

Something is either pulling it down, or a capacitor has failed and it can't go *up* far enough (story later).

The 15V rail did not show AC on the multimeter but appears to indicate 1.32V on the scope.

Believe the scope.

Should I be looking at the main caps or are there other places to check first?

Start to analyze the supply.?

The +15 volt supply has a bulk supply voltage of about 24.5.? There is a troubleshooting chart for power supplies in the service manual.? Look at the +24 volt bulk supply.? Is there 120 Hz ripple (or 100) on it or 60 Hz (or 50).? That can indicate a bad CR1541.? Is the supply being pulled down by an excessive load?? Check the voltage across R1549.? That ought to tell you how much current is being drawn.? (about 900 mv/amp).? Is the 55 volts exactly on?? That's the reference for this supply.? Check if C1549 is good or leaky.

Read the power supply theory and see how this supply works.? Don't feel bad about having to do so.? Most people, unless they do this for a living (and a lot of it) will go to that section and red it at least once.?

Check the voltages given in the circuit for normal operation.

Short story.? I have a 1000 volt (maximum) voltage reference.? Rather nice, you can adjust to about 1 microvolt on the one volt range and 1 millivolt on the thousand volt range.

I couldn't get it to go above about 200 volts.? I checked the amplifier, I checked a lot of the resistors, but it was only on the 1000 volt range that I had the problem.

Long story shortened, I finally looked at the supply that was to produce the 1000 volt bulk.? It was way low.? Looked at the supply with a scope (and high voltage probe).? Massive ripple.? The filter capacitors were bad, nothing else.? There was not enough sustained voltage to allow the circuit to produce 1000 volts, even though it hit over 1000 volts at the peak of the AC cycle.?

Two capacitors later, I had a working 1000 volt calibrator.? (DC only).?

Harvey