Hi Rick,
How wonderful those Mercury cells were!!!
Congratulations on snagging a 5S14!!! You are going to have a ball with it. The 7S14 and 5S14 plugins are fabulous!!! Those two plugins are truly amazing and completely unrecognized for the brilliant engineering that went into them. In an instant they can turn a simple 5000 series scope capable of only a few MHz into a 1GHz Dual Trace, Dual Time Base scope capable of rock solid triggering with XT as well as XY capability.

I did an extensive search for replacement batteries about a year ago thinking it might be possible to find ones that would last long enough to be worth adding battery holders so they could be easily replaced as needed. I was very disappointed by what I found. I will be the first to admit I may have missed some possibilities so maybe you can find something I missed.
What I found:
1) Either manufacturers no longer bother to make long life cells because there is no money in manufacturing something that may never need to be replaced, or none of the current battery technologies have leakage currents low enough to prevent them from self-discharging within a few years.
2) The relatively short lifetime of any current replacement is a major problem especially when you consider how annoying it will be to remove all the screws to get to the batteries every few years.
Other factors to consider with using cells:
3) Finding cells with the right voltage that have a stable (flat) output voltage over the cells lifetime.
4) Finding cells that will fit the tight space available.
5) Figuring out how to insulate the cell holder so it doesn't touch any nearby parts of the circuit but allows for easy cell replacement every few years.

I decided that replacing the mercury cells was impractical and the only solution was LEDs. I was looking for a small enough combination of LEDs to fit in the available space (I was going to try surface mount parts next) when other responsibilities got in the way. It is something I need to get back to.

Dennis Tillman W7pF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Rick
Sent: Thursday, December 24, 2020 10:10 AM
To: TekScopes@groups.io
Subject: Re: [TekScopes] tektronix 7S14 batteries and time base question

Love this thread. I am super excited for the delivery of a 5S14N this coming Monday. I assume the batteries will be too low. I'm torn between replacing the batteries and adding holders or go the LED route.

Rick

Since Sunday when I picked up 106 of Peter Keller's books we have spoken by
phone. During our conversation Peter mentioned a few things I thought I
should pass along since I thought he may have reached the wrong conclusion
from his brief time as a member of TekScopes.

Peter was disappointed that there didn't seem to be much interest in the 500
series of oscilloscopes. I thought it might be nice if Peter heard from how
many TekScopes members have 500 series scopes and what you like most about
your favorite model.

* Peter and I both agree that the pinnacle of the 500 series was the 547. I
was in love with the first one I got to use in 1967 shortly after it was
introduced. That was a fabulous scope!
* We both agree the 500 series was known worldwide for the incredibly tiny
CRT spot size.
* Peter felt the 500 series was the last scope anyone could fix since it
didn't use many specialized parts. I disagree about this because I have
spent years troubleshooting and repairing 7000 series plugins and
mainframes. Tektronix' fabulous documentation makes it just as easy to fix
these 7000 scopes as it does to fix the 500 series but that it just my
opinion.

From the volume of posts we receive it may appear that there is more

interest in the some of the portables but that is because they are so often
broken, replacement parts are impossible to find, they use a lot of surface
mount and custom parts, and Tek stopped providing Circuit Descriptions,
Parts Lists, and schematics to assist in calibrating and repairing them.

Dennis Tillman W7pF

I didn't get an answer, and no longer have a 475A. I do, of course, have too many scopes.

Thanks Paul!

I see I've scored. I'm going to have to pick your brain on this subject. That is, take advantage of the accumulated wealth of knowledge of the community. You guys are great.

I want to keep this conversation on the forum for the time being as the first thing I've been doing so far is searching and review threads with regards to 465 power caps. It's paying big dividends so far. But it is challenging to peruse the vast results. I'll do a search for adapter boards as this is the first I've heard of it, and am kind of liking the idea. The 465 PS Cap Replacement Guide is good, but I'd like to implement it a little neater. That's no dig against the original writer. We're all indebted for the shared experience. So hopefully my experiences and this conversation can contribute to the knowledge base.

I'm a little on the fence about the wholesale replacement of the original caps, but then I'm an ignorant newb. I hear your point about prophylactic replacement. I'll have to dwell on it for my own comfort. Also know that I replaced C1419/C1418 with new Nichicon ULD 60v caps, so I'm not a original preservationist. I guess I want to strike a balance between need and the risks and efforts of wholesale replacement. I suspect the adapter boards are constructed for replacement of all 5 big caps. I do like the assurance that new over-spec'ed caps provide.

As I say, I'll do some research, but if you have particular advice for adapter boards I'd love to hear from you.

Thanks again!
Dave

  Ed, how serendipitous.

I too am looking at a power supply cap issue. Haven't nailed it down yet, but similar line frequency "ripple". In my case the "ripple" is more like unregulated/unfiltered full-wave rectifier output on the 120v and/or 55v rectifier output - there's no significant capacitance. Question is, which cap.

What caught my eye here was "I have the caps on hand". Do you mean you have a stock of original 465 PS caps? Or do you mean you have a supply of modern caps?

I've looked at the "465 Power Supply Capacitor Replacement Guide", and am feeling a little more confident about attacking these caps. But I'm still on the fence about what route I would want to go. I'm very much the "ain't broke, don't fix" kind of guy, and I'll say I'm 51% biased towards keeping things as original as possible.

Curious to know what you meant by on hand, and if you have suggestions for sources.

Dave


  On Thursday, December 24, 2020, 09:11:31 AM PST, Ed Pavlovic <kc9mmm@...> wrote:

  I recently picked up a used Tek 465 scope for a price I liked and could pick
it up without having is shipped, and I'm getting started on checking it
over.  Everything works, although both traces even when grounded look like
there's an uncompensated probe attached.  But I figured I would look at the
low voltage power rails before I try to track down that issue.  Early 465,
with a B010XXX serial number, needs some cleaning and TLC.



All the test points for the rails except the -8 volt are within spec which
was low, so I hooked up a probe to the test point.  I'm getting a 1.75 volt
ripple at a frequency of 120 Hz, which makes me suspect the filter cap is
bad.  I have the caps on hand to replace all of those power supply caps on
all the rails, but before I go and do that, I just figured I would ask if I
should look at anything else on this power rail before I change the filter
cap so I don't kill it right away.  There's also a 33uf tantalum cap on that
rail to ground that I will replace as well as the service manual calls it
out as a 10 volt rated cap, which isn't much to spare on 8 volts.

I uploaded a photo to a folder I created of a shot of the ripple on the -8
volt rail here:



https://groups.io/g/TekScopes/photo/258534/0?p=Created,,,20,2,0,0



If the link doesn't work the name of the folder is "Tek 465 Negative 8 volt
rail" and there's only one picture in there.



Ed Pavlovic

KC9MMM













!DSPAM:5fe4d72d33731209017941!

-----Original Message-----
From: Fabio Trevisan
Sent: Tuesday, February 19, 2019 1:12 PM

Hello,
My first Tek, I used to own until a few months ago, had a weak CRT
since day one (when I got it from a local, Brazilian auction site).
One of the first thing that I noticed, besides the low intensity, was
that it had this double-peaking thing (which I was unfamiliar with).
It was when I joined this group and the messages should still be there.
Back then David Hess (where's him? Haven't seen anything from him for
a
while) pointed me to Ed Breya (both are renowned members), as Ed had
some experience in rejuvenating CRTs.
At the same time, I learnt about the extensive information available
on the tekwiki site (google for TekWiki... you'll find it).
At TekWiki, there in the "Manuals, Catalogs and Other Publications",
there's a section called "Concepts Series".
Between the "Concepts Series" publications, the very first one is the
"Oscilloscope Cathode-Ray Tubes, 2nd ed.
LInk here for your convenience:
http://w140.com/tekwiki/images/6/62/062-0852-
01.pdf
Between pages 10 and 14 there's a detailed explanation of how the
electric field lines from the grid interact with that of the cathode,
to create an electrical equivalent to a photo camera's "aperture"
ring... which is actually what broadens or pinches how much of the Cathode surface is "opened"
for emissions.
So,, follows what I conclude from the understanding:
When set to a lower intensity, the cathode effectively emits only from
the center, and as we crank up the intensity, it opens up more and
more area of the cathode to emit the beam. Therefore, the center of
the cathode is the most used portion and is the one that wears out first.
As the CRT ages, the central spot of the cathode wears out and you can
only obtain some intensity as you open the "aperture"more and more,
exposing the next section (an emitting ring now, not anymore a circle).
That concentric wearing "pattern" ends up imprinted on the cathode
and, in my opinion, is what causes the double peaking...
On a worn out cathode, when you start cranking up the brightness,
initially the aperture is drawing electrons from the "worn out" area
which, despite it's worn out, it responds to the intensity
control...(more C.W. more brightness, only that at a lesser degree"...
As you keep opening up the "aperture", you expose more and more of the
outer rings (which are also more worn out than the center, so the
intensity decreases)...
Up until a point that you open the aperture so much that you expose
the outermost ring of the cathode which is still not worn out...
(thus, enters the second "peak").
At this point, although you managed to get more electrons and more
beam intensity, the size of the spot is already too big and the
Focusing anode can no longer focus the beam correctly... (or the Focus
Tracking potentiometer can no longer track correctly the increase of
the intensity control) and ultimately, the Focus and Astigmatism is ruined.

Part of my conclusion can be flawed, but overall, I think this is the
mechanism.

Rgrds,

Fabio