Q for the Avionics Techs

[WG774]

Hi,

As I’m sure some of you are aware, there are still a few plants (mainly in Russia and China, one or two in the US) manufacturing thermionic valves. I recently read on a forum relating to Russian a/c that there are supposedly still certain Russian military a/c currently in the air using Avionic systems that implement valves, does anyone know if this is accurate information?

Obviously a/c such as the Fishbed or Mig-25 (for example), originally used valve-based systems, but I would have thought these systems to be updated with solid-state by now? From what I understand, thermionic valves are virtually immune to the effects of EMP (Electro Magnetic Pulse, generated by a thermo-nuclear explosion), and as such I would imagine there could be a firm reason for retaining them in certain systems or backup systems allowing for the consequence of a nuclear strike?

I’ve read here in the Nostalgia forum that there is a valve requirement for certain classic a/c, but what about a/c still in military service in Russia / China / Asia etc?

It would be interesting to hear from anyone that was around in the ‘60s when the move to solid-state begun, any recollections? Were you concerned about the reliability of early s/state systems?

Thanks in advance.

[Blacksheep]

Our British 'V' force were full of thermionic valves that saw active service over the Third Reich - not to mention the good old recently retired Shackleton - and there was no way that most of their kit would or even could ever be upgraded to solid state. There are certain advantages to using thermionic valves, especially in military applications [as well as top-of-the-range domestic audio systems!], and immunity to electronic pulses generated by nuclear detonations is only one of them. Plenty of the remaining 'Second World' military aircraft date back to the sixties, so I'm sure that a lot of thermionic avionic equipment remains in active service.

When I was an apprentice we learned lots of complicated thermionic theory that no-one bothers with very much today, right up to the heptode - try reproducing that fabled contraption in a solid state circuit! At the same time we were taught 'new' transistor circuitry that would be considered very primitive by today's electronic wizards. It impressed us though and we were promised greater reliability- a promise that was certainly delivered in no uncertain terms. The disappearance of the cosy glow from the valve heaters made trouble-shooting a lot more difficult though...

Many of our tutors had their doubts about the new technology and I recall old 'Wally' Parkhouse refusing to have anything to do with the large power transistor that replaced a triode switching valve in his beloved "Wide Speed Range" generating system. Wally would call another instructor into the class at any time his meanderings around the circuit encountered the dreaded 'transistor thingummajig'.

[WG774]

Thanks for the reply Blacksheep :ok:

I wasn't sure if here was the right forum to put this question in - may I ask if anyone here knows of a forum where the avionics techies hang-out? I'm looking into the prospect of a part-time degree in electronics; there are plenty of good forums for general RF/Digital stuff, but a link to a specialist avionics group would be useful for getting in touch with current issues as well as general theory.

Cheers!

[SeldomFixit]

Time to turn up your MagAmp Blacky !!!! :ok: