I did replace the diode and it restored everything to normal operation.
It's interesting how some of us learned electronics, soldering, etc. I use it so rarely.
I think back and it didn't really have any practical application back then, just hobby stuff
shortwave radio, the transistor was pretty cool, no more 67-1/2 volt batteries.
I presume we're talking about the electronics on this old scope - sorry, but I cannot help myself after reading Robert's last post above...the "standards" were 45V, 67.5V & 90V batteries in the days of valve electronics...different voltages used for supplying the plate (anode) ("high tension") voltages of different valves/tubes in portable stuff...these batteries usually lasted a fair time because the current draw was very low; as a kid I pulled apart quite a few of these batteries laying around our house. The filaments for the cathodes were lower voltage & drew quite a bit more current & lasted much shorter between replacements...the higher voltage ones could really bite if you stuck your tongue across the terminals!