Decided to check the compensation on the Tek 465B. Months ago after I completed all the repairs I basically just did some quick waveform checks and called it good. So today more extensive testing.
Channel 1 was OK. No adjustments needed. Channel 2 on the other hand was exhibiting noisy switch contacts again so I tore it down to clean it.
First pix is the attenuator cover removed and the attenuator blocks pulled off. I sprayed all the contacts with deoxit then worked the switch back and forth. Let it sit for a few minutes then hosed it down with 100% IPA to flush out the Deoxit. Then dry with a blow dryer.
Close up of the attenuator board with the blocks removed.
Reinstalled the attenuator blocks and fired it up. Surprisingly the compensation looked OK. And everything was going well until I started inputting high frequencies such as 1MHz. The deck went completely noisy again with what looked like poor contact. But when I went back down to 1KHz it was rock stable. After working on this for a while and thinking it through I've come to the conclusion that the transmission lines in this attenuator assembly are just plain worn out and is causing roll off or have been damaged somehow by high voltage. Seems replacement is the only solution. Unfortunately the 465 parts mule I have uses a different attenuator assembly. So until I find a replacement channel 2 on this scope essentially useless. Oh well, have plenty of alternative scopes and this guy will just be a 1 channel scope.
All was not lost though. I also calibrated the DM44.