I just got a Tektronix 475 from ebay. The fan spins, lights come on, but there’s no trace and no dot when I hit “beam finder”. I measured the power supply test points and got these results:
+5: 4.99v, 48.5 ohm to ground, 0mv ripple voltage
-8: -7.96v, 40.8 ohm, 0mv ripple
+15: 14.98v, 68 ohm, 4mv ripple
+50: 50.00v, 2.78k ohm, 36v* ripple
+50 unregulated: 67v, OL, 31.9v* ripple
+105/160: 139.4v, OL, 13.8v* ripple
+110: 111.1v, OL, 20.9v* ripple
* where I measured high ripple voltages, my multimeter switched back and forth from That voltage to zero in about 1 second intervals. Not sure what that means.
The resistance on the +5, -8, and +15 volt rails seems very low, is that normal? I didn’t see any expected values in the service manual (although I haven’t read too deep).
I also noticed some kind of corrosion around where the giant caps(?) are.
It might be worth noting that the beam finder seemed to work on the ebay listing, but I haven’t been able to make it work.
I’m new here and fairly new to electronics in general so I’d appreciate any help. Thanks!