A couple of months ago I got myself through a long and tedious work project by placing optimistically low bids on various members of the 2465 family. I kept losing but it was a good distraction. One day I won an auction for a 2465a, $200 shipped. Giddy with joy I looked up the item description and found that somehow I'd overlooked a key sentence: 'The display doesn't seem to be working quite right.' Well, good, I thought, a little repair project to look forward to after the work slog. Then I did some googling to see what could go wrong with a 2465a display and learned about the failure-prone U800 horizontal amplifier. Just last week I saw a salvaged one listed on ebay for $195 plus shipping, offered by a fellow who takes the trouble to explain how ebay and paypal fees work and how he's really making only $169 on the deal, and don't forget, 'Part of that $169 pays for the surgical skill that does not lose any of the IC's 24 legs.' He adds: 'If you figure out any other way I get to keep $169 that costs you less, I'll accept.' I wonder how many under-the-table sales are facilitated by ebay.
When you are waiting for a package that will contain non-returnable, non-refundable proof of your own folly, you start to hope that it will be lost in transit. Mine wasn't. When it arrived I cleared some space on the desk and held a ceremonial powering-on--for closure, as they say. Readout, cursors, and a trace appeared, and after about a minute they started to move. But their motion was not the slow sideways drift that signals U800 failure. It began as a tremor, grew into a flicker, then escalated into a rapid oscillation. On the vertical axis. Things started to look up, so to speak.
Meanwhile, the transformer on the high-voltage board that supplies the CRT was rattling like a joy buzzer, keeping time with the jittery display. Here's where my luck really started to change. I know one rule for troubleshooting electronics, namely: Um, maybe it's a bad electrolytic capacitor? And happily this turned out to be the only rule I needed. After studying the schematics I headed straight for the filter cap on the unregulated -15V line leading to the high-voltage board (a journey that took much longer than expected) and tested it for ESR using another scope and a function generator. Bingo. Replaced it a few days later, putting an end to the song and dance.