[AT] was generator=ee / tubes

[Ken Knierim]

While tubes have been removed and replaced over the years in a lot of
systems, I found one recently that the modern electronics weren't able
to cope with.

There's a controller for the turbochargers on some radial-powered
4-engine aircraft (several different ones, actually) that some folks
had tried to replace with modern electronics. Apparently they didn't
get the system right because it ended up being removed and replaced
with the original, 4-tube amplifier systems. The problem with the
aging electronics is that the resistors are unreadable and the
capacitors are literally falling apart (cases splitting, etc). I'm
sure they never expected something build during WWII to still be
flying today, and all the discussions with the obsolete electronics
apply here: nobody really seems to know enough about them to want to
go in and repair them (me included).

     So when I was asked to see if I could repair or update the old
controllers, I looked it all over and opted for a mix of technologies.
The tubes were pretty much a requirement, since they worked and the
folks have a long history of testing and maintaining that equipment.
The point-to-point electronics were too rotted to repair, and the
transformers had been overheated and needed replacement as well.
      I offered to replace the point-to-point with a circuit board,
put in new transformers (and worked with a shop to do the 400 Hz
transformers). I also had to learn how to work with tubes. We touched
on them in electronics school when I was there in the early 80's, but
that had been awhile. I had to learn how they worked electrically in
the circuit (yeah, the FET terminology is valid, but which type? I use
a lot of MOSFETS these days... :). When I got the first ones complete
and we tested them, I don't know who was happier... the customer or
myself. They love the look of them; they still have the tubes they are
familiar with, and they have new parts and components, reducing the
intermittent "issues" the old controllers were experiencing.
     Out the other end of it, I've received an education on tubes, the
museum has a bunch of new parts (at a seriously reduced cost; I didn't
charge them for the engineering time) and I have some pictures that
will eventually go on my website. :) Oh, and the pride of keeping at
least one old warbird flying a little longer.
    It's been quite an experience, and there was another rewarding
aspect of it. My retired neighbor who at one point worked for
Honeywell in Minneapolis, looked at the controller and perked up. He
knew the guy that designed it (apparently a lead engineer at Honeywell
back in the day) and was quite happy to see the modernized version
being built new over 60 years later. (My neighbor is also quite a
storied individual, having served on the West Virginia after it was
salvaged from Pearl Harbor, and later on designed and built gyroscopes
that are still in production 40+ years later).
   So not all of the "modern" electronics will be thrown in the trash
when they reach the end of their usable lifetimes. I think many of the
modernizations are way overzealous in the application of complexity,
but I think we also see that in some of the old tractors. The ones
that were too complex either got simplified or didn't survive in the
field or in the marketplace. They are sometimes known as orphans or
oddballs. History will repeat itself, I'm sure.

Ken in AZ


On 6/19/06, Chris Britton <c.britton at worldnet.att.net> wrote:
> >From: "Thomas O. Mehrkam" <tomehrkam at houston.rr.com>
> >If you knew what a FET was you are younger than Me.
> >BiPolar transistors where the vogue. I do not remember learning about
> FET's. But it has been a long time.
>
> Bipolars were also what I started working with.
>
> >My first engineering Job was converting some Peanut Sorter machines from
> >Vacuum tubes to Transistor electronics. Planter Peanuts had a couple of
> >factories full of these Vacuum tube machines and wanted them refurbished.
>
> neat job!
>
> >I sure would of loved to had access to some decent FET's for that
> >project. I got rid of all the tubes except for the Photo Multipliers. I
> >tried Silicon sensors but at that time there were none that would work
> >without changing all the optics.
>
> As much as I like dthe bipolar transistors.. i also agree.. I'v built way
> more ( and more stable ) circuits using a fet of some sort...   Though have
> to throw kudos to the other stuff.. darlington pairs, and scr's.. etc.
> 'Bout the only thing i did with bipolars much was audio application.. ..
> input and output stages.. but thru the years... mosfets became the thing for
> the output stages...   .. Oh well..
>
> >You do remember having to repair TV's don't you.
>
> I can remember doing it for a few years... When it got to the point that you
> just replaced the mainboard.. I lost interest..  ( so did everybody else...
> big companies pretty much obsoleted small appliance repair.. )
>
> Soundguy
>
>
>
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