Re: Tek 310 and Looking for Advice

stan mcintosh <mcintosh@...>

Thanks for the advice. It helped rule some items in and some out. I hope
we're getting closer.

From Morris and Stan, respectively...

Check or try replacing the 5651 voltage reference tube. There >>should be
exactly 87 volts across it when it's lit.

Have you checked the output from the 5651 reference tube? It should be
about 85 volts. Measure this between pins 1 and 7 on V613.
The NOS 5651 that I put in 1-2 weeks ago had a 77 volt drop! The next one
had a 106 volt drop, and it *was* lit. The next two had voltage drops of
83.5 volts. I have one more in a box, but I decided that an 83.5 volt drop
tube would work for checking out a few of the other items.

From Stan (as are the rest of the quotes):

I still think the problem you see now is in the power supplies themselves.
Oh, I'm hoping it's restricted to the supplies. I'd rather chase a gremlin
through a small section rather than the whole scope.

Are the power supplies "regulating"? That is, do the voltages remain the
same as the line voltage is varied from 105 to 125 VAC? If you don't have
metered variable line voltage source, now is the time to get one.
Here is where we see some differentiation. From 105-125VAC input: the +100
V regulates right at 59V, the -150 regulates at -139, and the +300 swings
from 270 to 290. I don't have a metered line voltage source, but I do have
a voltmeter for making such measurements when using a Variac input.

How much "ripple" is on each supply? Is is about the amount stated in the
manual calibration procedure? (10 millivolts)
The ripple values in the +300, +100, and -150 are 3 mV, 1 mV, and 3 mV,

As you try to set the -150 volt power supply on -150, can you vary it at
with the adjustment control or is it just at -140 all the time?
The adjustment does affect the -150 output voltage.

I'm going to have a cold one and pore over the power supply schematic,
again. However, I'm hoping that you'll effortlessly say, "Ah-Ha! You
obviously failed to check ..."

Again, thanks for all of the help. If this scope didn't have so much
character, and if I didn't really want it to be part of my bench, I'd go
back to working on my superhet.


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