Re: Type 503 Oscilloscope Issues

Dave Casey

You can leave V692 in there while you attempt to adjust the voltages. The
-100V supply is the feedback to the error amplifier and is thus the only
one you can easily adjust. The +85 from the regulator tube is a reference
voltage for the error amplifier. When everything is rock solid, you should
have about -2V on the wiper of the -100V adjust pot.

Dave Casey

On Apr 20, 2017 12:21 AM, "enchanter464@... [TekScopes]" <
TekScopes@...> wrote:

To Mike's first point, the analog voltmeter is correct, since that was
calibrated when I repaired it a few weeks ago. However, the digital
multimeter is inaccurate, and I am not sure why. It is a Beckman 3030 that
I got after accidentally frying the RadioShack one (had a fuse blown)
during the first round of scope measurements to confirm those from the
analog meter. However, compared to another multimeter I have, the Beckman
was off by a factor of 1.1. Using this to correct the previous values I
reported, the values now match more similarly to those that were measured
by the analog voltmeter. As such, I will base any calibrations on the
oscilloscope using the analog meter.

And not to worry about the pin mistype. I saw in the manual that the
orange wires corresponded to the -3 kV, and that was for pin 7. I did not
know to remove pin 6 at the time, which is why i went ahead with just
removing V692 for that round of voltage readings. But all is good now.

I still cannot check the -3 kV without getting probes that can support
that, but I did go ahead and order the transformer that Dave suggested (the
Triad F-313X, 6.3 VAC out, 120 VAC in, 600 mA, 2500 Vrms isolation). That
should be in next week.

In the meantime, should I go ahead and calibrate the voltages while V692
is installed, or should I remove that again (in addition to already having
Pins 6 and 7 disconnected from T601)?

Also, to Dave, a wiring schematic (or just instructions for the pin
wiring) would be very helpful, but no rush since the transformer will take
time to come in.

- Evan

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