Psychotic Oscilloscope Idea: Tube to Transistor

[PhynixViking]

Ok, yea as the title says I have a crazy idea... how hard to you think it would be to COMPLETELY convert a old 1960's 2CH oscilloscope to be completely transistor based? (except for the CRT of course)

Why would I? Well its kinda a nice oscilloscope but I'm afraid the tubes are going to burn out any day. I believe they are mostly the original tubes most of them the ink is long-gone worn off... as well as it might be a fun project to help me learn more about tubes and transistors.

Is there some place that has a "tube to transistor conversion schematic" or something?

[c4757p]

The transistor type that is closest to the vacuum triode is the N-channel JFET. By the time you locate and purchase a set of JFETs with the voltage and power ratings of triodes you might as well have replaced either the tubes or the entire scope. Good luck if they have anything involving more electrodes than a triode and they're doing something unconventional with it. And fitting in anything but a JFET into that circuit is tantamount to designing your own oscilloscope from the ground up. Note that even if you did put in JFETs and by magical coincidence they were similar enough to work, you'd still have to rebias the whole circuit.

Interestingly, there were at one time solid-state tube replacements that were JFETs with some circuitry to compensate for differences in characteristics. Most of them only worked properly in specific circuits.

[MartinX]

I have also had this idea and then rejected it, it will take forever to figure out how each tube is used and then build a transistor equivalent that fits. I thought it was a better idea to replace an entire function block in the scope, like the vertical amplifier with a modern circuit having the same function, in the end I found a more modern scope that I could afford, so I still have the old scope in its original condition and now I am glad I didn't destroy it.

[SeanB]

Most scope tubes are pretty common types, and are available as either NOS or current production from Soviet era factories.  For the few that are made of unobtanium there are modifications to use more modern components in their place.