On a recent trip to Portland, I stopped by Surplus Gizmos, and found a used, as-is, Tektronix 2465 scope that had a calibration sticker on it saying “unit smoked while calibrating”. The scope was listed as $100, but I was able to get it for $60. I know the unit isn’t worth a ton, but it is a 300Mhz scope, and is seemingly considered one of the best Tektronix scopes ever (it’s also considered the last repairable Tek scope, as after this, most scope manufacturers stopped including schematics and other information with the scope). Also, the unit showed to have been manufactured around 1984, which is when my grandfather still worked at Tektronix writing manuals for scopes. So he may have very well worked on the manual for this scope.
Opening the scope up, I figured the issue was going to be the power supply, as that seems to be the common failure in this scope, and really any device of this age. The capacitors dry out, change ESR, overheat, blow, etc. Getting the fan off was really the hardest part of getting the power supply out, but once I figured that out (and broke the mandril holding the fan. =/) I got the PSU out, and quickly found the failure points1. One of the caps on the low voltage side had ruptured, and also R1016 and C1016 on the mains input were both blown. There are plenty of online guides about re-capping this scope, but the only one I found with actual part numbers and quantities was here. His list is for the 2465B, but the 2465 is very similar as far as the PSU, the main difference is the lack of the SMD caps that everyone says to replace. Instead, there are three through-hole caps on the Digital board that you can replace.
- Note, to remove the fan, you loosen the nut, then holding the fan “cage”, PUSH on the nut-screw toward the scope. That will push out the mandril and release it from the shaft. If it won’t release, please be careful. I got lucky and my mandril broke in a repairable way. I’ve seen pictures where they completely shatter, and there don’t seem to be any replacements available [↩]