Calibrating the Tektronix 2225

The shop is really freaking cold right now.  February and early March was brutal and snowy, and I keep the shop thermostat set just a few degrees above freezing.  I do this to minimize propane use, while also preventing the plumbing from freezing.

Today the outside temperature got as high as 52, and snowmelt was pouring off the shop roof.  Inside however, it was like an icebox.  The shop is well insulated, and the concrete floor is just above freezing, as it has been all winter.  It will be a long time before that heats up again!

One spring I tried to get the shop up to temperature quickly.  I adjusted the thermostat up to 65 degrees for a couple of days.  I burned through 100 gallons of propane in two days, and the shop still wanted to cool down due to the concrete still being pretty cold.

Today I just rolled up the shop door and turned on the ceiling fans.  That warmth was free.  My feet got pretty cold though.

I was calibrating the good 2225 Tektronix oscilloscope.  The manual is pretty straight forward on how to accomplish it.  My cheap Chinese signal generator on the other hand, doesn't have the ability to output the signals needed.  So I'm doing what I can as best I can.

First you adjust the main board voltage, then you adjust the CRT bias, astigmatism, and rotation.  Then you move on to the vertical adjustments for channel A and B.  After that come the horizontal adjustments, which I ran out of time for.

Before starting, I needed more room on the workbench.  I put aside the two Fluke 8000A meters to make room for the Isolation Transformer, at the left. The Instek meters stacked at the center are quite a bit better anyway.

So here is the set-up.  The laptop on the right has software to display a virtual control panel that drives a signal generator.  The signal generator is the little device with the yellow-green display.  The signal generator creates a high-frequency radio signal that is fed to the oscilloscope at the left.  Then you tweak little controls on the main circuit board to make the CRT screen correctly show the signal that you are feeding into the scope.

There are plenty of adjustments to make while calibrating this thing!  At the end of each yellow line is an internal adjustment.  It's about a 20 page process.

I'm hoping to get back to the faulty 2225, the one with the noisy channels, in the near future.  Just need a couple days off work with no chores at home!