My faithful old Tektronix 465 has recently been experiencing issues with the delay function for the secondary horizontal timebase.

For those not familiar with this feature, here is a quick explanation: the Tek 465 has dual timebases. You can set up timebase A for say 1 millisecond per division and timebase B for say 10 microseconds per division and switch the horizontal timebase from A to B as the raster scans across the screen. This is useful when you want to zoom into the details of a signal sometime after triggering as the raster is partway across the screen. This switch in timebases can be by trigger or by a delay feature.

It’s basically a controllable zoom capability. I find the time delay version of this feature most useful, but recently I found that when the change in timebases was set to delay, it would trigger immediately, instead of delaying.

After several debug sessions, the feature started working intermittently. This slight improvement in behavior started after probing in the area of several suspect transistors. I pulled the most likely transistor out of it’s socket and tested it using a diode tester. It tested good. After reseating it and some other transistors, the feature seems to working reliably again, though only time will tell for sure.

Anyway I took a good look at some relevant signals while it is working, so I’ll have a better shot at debugging it, if the problem crops up again.

There is nothing worse than intermittent sockets and connectors. I’ve had this scope for a long time and it has served me well, but maybe it’s starting to show it’s age a bit. By the way, as I don’t have a second scope, once again, I used this scope to debug it’s own issues.