Tektronix 577 curve tracer

I have finally pulled out my Tektronix 577.

It arrived with a few screws lose inside it, and the cover on one side has been removed and replaced incorrectly. Not a good sign.

It turns out that the top and bottom section (the top section contains the CRT) were separated at the back and those screws seem to be the sort that will hold it together (more bad signs)

And now I notice that the asset ID on the cover is different from the asset ID on the front of the unit.

I'm beginning to think it's a Franken-machine.

Oh, and did I tell you it came from a school or college or somesuch?

A power (after changing the voltage) on suggests that it's at least kinda working. I can find the brightness and focus (which work), but there's so many controls I don't want to risk stuff happening so I turn it off.

Armed with 10 pages of the manual, a resistor and a diode, in ready to test it.

Some of the controls are noisy, but here is a diode under test:



And a close-up of the screen:



Attacking the lower section with contact cleaner (the lower section can be removed -- explaining the different IDs) fixes up the problems with these controls, but I'm going to have to clean up the rest too (especially the switches)

I also looked at the reverse voltage behaviour of the diode, and while the breakdown starts with a nice curve, the eventual avalanche breakdown is really noisy. This diode would make a really ugly zener diode!

I'm about to clean up the front panel switches, and I'll get back to you...

Oh, it's also worth noting that the minimum X range is 0.1 V/div which is really not the greatest for looking at forward biased diodes.

Edit: it's a 577, the 177 is the bit at the bottom!