Re: A Vacuum Tube Curve Tracer for all Tek Semiconductor Curve Tracers

Dave Casey
 

I've been planning to build a tube tester base for the 577 out of a
scrapped 177. I was hoping I could leach the grid supply off the 577, but
there's no telling if the transformer has the margin to support that.
Heater supplies would be provided externally from a trashed tube tester. I
was going to mimic a bit of the 570 implementation and use banana leads to
patch the tube pins. This is potentially more cumbersome, but way cheaper
and smaller than a switch matrix. Any bias voltages I want to measure can
easily be tapped off the banana stack to a bench meter.
Yes, I will have to make several "base plates" for various sockets and
patch them differently depending on whether I'm trying to match sections
within the same tube or multiple tubes, but I'm hoping I can keep the
parasitic inductances to a minimum by leveraging as much Tek-designed
circuitry as possible. Dennis' add on amplifier circuit will almost
certainly make it's way into the fixture (if not, something similar will
have to in order to get useful data).
Great job on putting this together and documenting your work!

Dave Casey

On Tue, Mar 14, 2017 at 4:45 PM, 'Dennis Tillman' @Dennis_Tillman_W7PF
[TekScopes] <TekScopes@...> wrote:



Hi Ed,

Fortunately you picked mostly the easiest to find sockets. I can't recall
if
I saw the Nuvistor and the subminiature in-line sockets anywhere. But as
you
said the others are the "normal" ones that are readily available today from
several places for a few $ each here in the US.

I think you are forgetting the value of your time. It will take time and
tools to cutout holes in a chassis and run the wiring to these sockets. In
addition you need a way to assign heater, plate, grid, and screen voltages
to different pins depending on which tube you are testing so that involves
a
switching matrix of some kind. The other pins have to be grounded or opened
depending on what they might have to do.

For instance there are a lot of pentode-triode dual tubes which have to be
tested in two parts and the other part has to be shut off or disabled. SO
in
reality for a 9 pin tube you have 9 switches that have to connect to
heater,
grid, screen, plate, open or ground. For a Compactron you need 12 six
position switches.

When you take all of this into account a tube tester starts to make a lot
of
sense even of it costs $100 to $150.

As I said, I will be glad to help you find something here and ship it to
you.

Dennis

-----Original Message-----
From: TekScopes@... [mailto:TekScopes@...]
Sent: Tuesday, March 14, 2017 2:04 PM
To: TekScopes@...
Subject: RE: [TekScopes] A Vacuum Tube Curve Tracer for all Tek
Semiconductor Curve Tracers

Tube socket availability may not be so dire, depending on what variety of
tubes need testing. If you want it universal to cover everything, do as
Dennis recommends and get an old tube tester - even a spendy one would
probably be cheaper than acquiring all those obscure sockets.

But, if like me, you only need to do a few, more common (and modern) types,
then it can be simplified. If some occasion comes up where you need one of
those oddball ones, you can rig up an adapter or even alligator clips in
lieu of a socket. For my 576 plug-in tube tester project, I've set set
aside
a bunch of the more "normal" ones - octal, 7&9 miniature, Nuvistor,
subminiature inline, a jack for a plate cap, and a connector TBD for
external adapting. I'm not a tube guy, so don't need the other stuff - I'm
mostly interested in maintaining some equipment with a fairly small variety
of tubes, while having the ability to look at other interesting ones out of
curiosity.

Ed

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Posted by: edbreya@...
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