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I bought a 465 (not B) off fleabay that supposedly had no beam. After testing it out it did in fact have a nice beam. I guess they did not know how to set it. However after a little while I noticed the beam would glitch. And when I turned on beam 2 it behaved as if it was stuck in Add Mode. The controls for trace 1 had an effect on trace 2.

I could not find any post here or with google that mentioned this error. Looking over the schematics I realized the only place trace 1 and 2 met was in the Alt, Add and Chop circuit so I began there. When I first open the case I went straight to the Add circuit and near the diode matrix I found a .02 ohm 150v ceramic resistor with a chunk missing. I thought I had found the problem. I removed it but the problem persisted and it actually still tested good. I replaced it with a .022 ohm 1kv I had on hand, I hope that is ok as the previous part is hard to locate.

I went though all 3 circuits multiple times and not trusting my in circuit reading I even took diodes out of circuit to test. I couldn't find any bad parts. I tried probing with a second oscope to see if I could find a point of entry for the error. Finally I surmised that the switch must be bad or there was as short. I removed the DM44 option to gain access to the switches. There was a jumper strap running behind the switches so i took a screwdriver and I pulled them out and secured them on a nearby stud so they would not fall back behind the switches. This corrected the problem. The scope is now happy.

I hope this helps someone else if they run into a similar problem.

Here's a picture of the strap /g/TekScopes/photo/63580/0?p=Name,,,20,1,0,0

I dont want to post bad info. I was up until 2am last night and I thought I had it licked before I went to bed.

I just powered up the scope and when I switch from channel one to channel two it is back in add mode. After about 20-30 sec this clears up and it works normally.

Could it be that it was in fact the capacitor that was at fault and the 1kv substitute is not responding as quickly as the 150v?

I want this scope to work perfectly. Its a very nice and clean scope.

Working on these scopes is like working on a classic car both rewarding and frustrating!

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I used to work on those old 465's and the diode switching circuits are fun to troubleshoot.? It was around 30 years ago, but you could check the diodes in circuit with the diode function of a DMM.? With the scope being that old
the switches maybe dirty?? Try some Deoxit in the back of?all the verticle mode switches, and exercise them, about ten to twenty times.??( You may need to remove verticle preamp board to get to the switches, or nozzle and
flashlight.??
Maybe some of the regular contributers? could chime in.
Later Ray Burke