After my previous antics with the 7834 readout system, the outcome was:

• U3401 Zeros logic & memory – tek part 155-0018 – the original culprit.  Replaced with one from ebay.
• U3418 Column decoder –  tek part 155-0014, which I think I killed during repairs. Replaced with one from ebay.
• U3477 7402 quad 2 input NOR gate – smoked during repairs.  Replaced with a 74ALS02 from stock.
• It turned out U3232, the row data switch that cycles through the 8 plugin display channels was bad as well,  botching the readout in horizontal A bottom, and horizontal B top & bottom.   Replacement sourced from ebay.

So far, I’ve spent $50 on the scope, and another $50 or so on replacement chips.  Still not bad at all.

Here’s a few shots using the 7B85’s delta time feature, which lets you do fun things like measure frequency, rise-time, and pulse-width directly using the on-screen delay time read-out.  Thanks to Peter on the TekWiki who’s entry on the 7B85 pointed out these features.

These photos are of a rudimentary clock circuit I made using parts from the DF01