Date   

Re: DM44 on a Tek 475B - what's the externally accessible adjustment?

Tom Gardner
 

On 24/12/20 19:31, Paul (AE4PN) wrote:
Hey, Tom, did you ever get an answer? I have a 475A with DM44 scope like that. It has what is known as "Mod PG" which was a mod developed for a big customer named IBM! Such scopes have some changes, most visible being the small toggle switch just to the right of the Delta TIME knob on the DM44 unit. And yes, in the DM44 there is the small circuit board add-on you have found. One of the purposes of the PG mod is to switch-enable the DM44's Delta TIME control to either track the 475A (or other scope) Delay Time Position (DTP) control or to operate independently of the DTP. In a non-PG DM44, the default mode is "Tracking" but one can change to "Independent" mode by changing the plug-in location of a 3-wire cable on the DM44's main board as well as position a jumper plug to an alternate position. I have a bit more info I can share. Also, what have you discovered? Anyone out there have a circuit diagram for "Mod PG"? Has anyone been successful in troubleshooting a DM44 with Mod PG?
I didn't get an answer, and no longer have a 475A. I do, of course, have too many scopes.


Re: Tek 465 Negative 8 volt rail issues

Ed Pavlovic
 

Dave,
I have current production caps that I just bought from Mouser. I specifically looked for smaller diameter caps so I wouldn’t have clearance issues between the caps, but a few I just couldn’t get as small as I wanted but they should work.

I did buy the adapters on eBay to get the same footprint as the original ones, I may use a small washer on the pins to make soldering then to the board easier. Not really looking forward to unsoldering the old cans.

I can post a list of what I bought, but I want to make sure everything fits before I do.

Ed


Re: Tek 465 Negative 8 volt rail issues

Paul Amaranth
 

If you search on ebay for "Tektronix capacitor adapter" you'll get a few hits.

Someone posted gerbers on eevblog if you want to send them out yourself. I
could probably find the link to that. Actually, here's one:

https://www.eevblog.com/forum/repair/making-dave_k_s-capacitor-adapters-at-osh-park/msg1218875/#msg1218875

I made up a pattern in a drawing program and etched some using
pnp-blue. That worked fine, but I just buy them now. A number of
people have independantly come up with this solution, a sure sign
it's a good idea :-)

You could likely use the gerbers if you had access to a pcb milling setup.

"Wholesale replacement of caps" in this instance only refers to the
metal can filter caps. Other than the odd shorted tant I've never had
to replace any other cap and, in general, if it ain't broke don't make
it so :-)

It's possible the other cans could be good for years. To accurately
check them though you'd need to pull them, so ...

An ESR meter might give you some good hints without pulling them. The
ESR will go up as the cap dries out so if you're seeing 100 ohms on a
470uf cap, it's a good candidate for replacement.

You could just replace the bad one and you'd be good for a while. When
I've tried that I'm back in there in a year or so anyway. At least
they don't leak all over and destroy the PCB.

Paul

On Thu, Dec 24, 2020 at 07:08:47PM +0000, Dave Peterson via groups.io wrote:
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
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Re: DM44 on a Tek 475B - what's the externally accessible adjustment?

Paul (AE4PN)
 

Hey, Tom, did you ever get an answer? I have a 475A with DM44 scope like that. It has what is known as "Mod PG" which was a mod developed for a big customer named IBM! Such scopes have some changes, most visible being the small toggle switch just to the right of the Delta TIME knob on the DM44 unit. And yes, in the DM44 there is the small circuit board add-on you have found. One of the purposes of the PG mod is to switch-enable the DM44's Delta TIME control to either track the 475A (or other scope) Delay Time Position (DTP) control or to operate independently of the DTP. In a non-PG DM44, the default mode is "Tracking" but one can change to "Independent" mode by changing the plug-in location of a 3-wire cable on the DM44's main board as well as position a jumper plug to an alternate position. I have a bit more info I can share. Also, what have you discovered? Anyone out there have a circuit diagram for "Mod PG"? Has anyone been successful in troubleshooting a DM44 with Mod PG?


Re: Tek 465 Negative 8 volt rail issues

Michael W. Lynch
 

Dave,

I have replaced several sets of these filter caps on the 465/68/475 series. Seller has multiple versions for different brands and types of equipment.

I used these:

Capacitor Adapter 15.5mm triangle recapping vintage equipment Tek 465 kit (x5)

eBay item number:
273254508468

Seller information:
cuog (749 )
100% Positive feedback

I believe that these are the ones that Paul is recommending in his earlier reply.

Good Luck!


--
Michael Lynch
Dardanelle, AR


Re: Tek 465 Negative 8 volt rail issues

Dave Peterson
 

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

On Thursday, December 24, 2020, 10:41:39 AM PST, Paul Amaranth <paul@auroragrp.com> wrote:

These caps dry out all the time, it's a very common problem.

The orginal cans are no longer available and, if you find some NOS
ones, they will probably dry out shortly if not already.

Get 105C snap caps and use one of the adapter board floating around to
match the footprint to the 4 terminal footprint of the original.  Use
high quality caps by Nichicon, Panasonic, etc.  Avoid cheap noname or
offbrand Chinese caps.

All 3 ground leads need to be jumpered since Tek used the can as a
jumper and the adapter boards take care of that for you. The adapter
boards make for a very professional repair.  I hate seeing caps hanging
off the board hot glued to something.

If I have to replace one, I generally replace all of them.  Then you
won't have to worry about it for 20 years.

By using very long leads on the adapter boards I have replaced the
caps in situ without pulling the main board by threading them down from
the top.

Unsoldering the main caps is fun, not.  It's easy to overheat the board
and have trace separation.  Be careful and use good desoldering tools
and technique for that.  Some chipquick wouldn't hurt.

  Paul

On Thu, Dec 24, 2020 at 05:59:34PM +0000, Dave Peterson via groups.io wrote:
  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@comcast.net> 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!
--
Paul Amaranth, GCIH            | Manchester MI, USA
Aurora Group of Michigan, LLC  |  Security, Systems & Software
paul@AuroraGrp.Com              |  Unix/Linux - We don't do windows


Mechanism of CRT Double Peaking (UPDATED)

 

Peter Keller just provided me with a revision to the 4th paragraph of my original explanation for why the brightness of a well-used CRT first brightens then dims before finally brightening again as the intensity control is increased (known as "Double Peaking"). Here is the updated explanation.
-----------
Under ordinary circumstances a cloud of electrons boil away from the surface of the cathode as a result of the heater heating it to incandescence in a vacuum. This is sometimes called the Edison Effect because he noticed it first in light bulb filaments. It is more correctly called Thermionic Emission. This cloud forms around the cathode and is known as the space charge region.

The cathode is intentionally coated with a material that lowers the work function. The work function determines how much energy will be required for an electron to leave the surface of the cathode and join the cloud of electrons surrounding the cathode. A low work function means more emission.

In ordinary circumstances the space charge region is the source of the electron beam, not the cathode. The cathode is "filling" the space charge region with electrons that will be attracted to a positively charged surface and ultimately focused along the way into a tight beam.

As the cathode ages the chemical coating used to lower the work function wears out. The space charge cloud can no longer provide enough electrons to form a bright beam. After depletion of the space cloud, the current is being drawn from the damaged center area of the cathode coating which decreases available current. Further increasing the intensity control (lowering the negative grid bias) begins to draw current from the undamaged periphery of the cathode and increases beam current again but with a resulting larger spot size.
-----------
Dennis Tillman W7pF

-----Original Message-----
Sent: Saturday, February 23, 2019 9:28 AM
Subject: RE: [TekScopes] Mechanism of CRT Double Peaking

Hi Fabio,
Your explanation is plausible except for one more bit of vacuum tube physics that has to be taken into account: Under ordinary circumstances a cloud of electrons boil away from the surface of the cathode as a result of the heater heating it to incandescence in a vacuum. This is sometimes called the Edison Effect because he noticed it first in light bulb filaments. It is more correctly called Thermionic Emission. This cloud forms around the cathode and is known as the space charge region.
The cathode is intentionally coated with a material that lowers the work function. The work function determines how much energy will be required for an electron to leave the surface of the cathode and join the cloud of electrons surrounding the cathode. A low work function means more emission.
In ordinary circumstances the space charge region is the source of the electron beam, not the cathode. The cathode is "filling" the space charge region with electrons that will be attracted to a positively charged surface and ultimately focused along the way into a tight beam.
As the cathode ages the chemical coating used to lower the work function wears out. The space charge cloud can no longer provide enough electrons to form a bright beam. The user turns the brightness up to compensate. This increases the positive voltage attracting the electrons. Eventually the user increases this positive voltage to the point where the space charge region is completely depleted and electrons are being stripped directly off the cathode increasing the brightness temporarily. This is not good.
There is a way to extend the life of the cathode in a CRT as most people who worked in a TV repair store are familiar with it. I recall it as "rejuvenation". It is a simple process. If you increase the voltage going to the heater this will heat the cathode to a very high temperature which will burn off the weakly emitting surface of the cathode exposing fresh chemical coating from underneath. There is the risk of burning out the filament that must be considered when you do this. There is another variation of this which boosted the filament voltage on a permanent basis. This allowed customers to temporarily get more life out of a weak filament. Since filament life decreases rapidly with increasing voltage this won't postpone the need for a new CRT for very long. As you mentioned Ed Breya has some experience with this process so maybe he can explain it in more detail.

For more on the subject of Space Charge you can go to:
https://en.wikipedia.org/wiki/Space_charge
https://en.wikipedia.org/wiki/Thermionic_emission
https://en.wikipedia.org/wiki/Grid-leak_detector
https://en.wikipedia.org/wiki/Vacuum_tube

Dennis Tillman W7PF

-----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



--
Dennis Tillman W7pF
TekScopes Moderator


Re: Comments from Peter Keller on the 500 Series Scopes

 

My first experience with a 500 series scope was at KPFK-FM radio's engineering shop, as a teenage apprentice to the assistant chief engineer. I wasn't allowed to touch most of the test gear in the shop, though they did make me very familiar with the use of the Hickok tube tester and the Simpson 260 VOM right away as there was a ton of gear with tubes and relays all over the radio station. There was a 465 that belonged to the Chief Engineer but it was kept in a locker. There was a RM503 that I would play with when no one was around, and even as a very wet behind the ears tech could tell that it was a great piece of gear. The differential inputs were great because everything in a radio station is balanced, so it was actually better than the 465 for audio work. I have since then owned multiple RM503's and still think it's a fantastic X/Y scope.

Recently I acquired a beautiful "Hanger Queen" 545B that came with the matching 602-2 cart, stuffed with a 1A2, 7L5, and a 7L10. It had been always covered with the 016-0068-00 protective cover, and didn't have a spec of dust in it when opened for inspection. Incredibly, it fired right up, everything works, and is in reasonable cal! What a pleasure it is to use this 50 year old scope! I do like my 7K and TM500 scopes a lot, and use them on a weekly basis to fix broken stuff, but this 545B is like a time capsule of an America that could produce amazing industrial art that was functional.


Re: Tek 465 Negative 8 volt rail issues

Paul Amaranth
 

These caps dry out all the time, it's a very common problem.

The orginal cans are no longer available and, if you find some NOS
ones, they will probably dry out shortly if not already.

Get 105C snap caps and use one of the adapter board floating around to
match the footprint to the 4 terminal footprint of the original. Use
high quality caps by Nichicon, Panasonic, etc. Avoid cheap noname or
offbrand Chinese caps.

All 3 ground leads need to be jumpered since Tek used the can as a
jumper and the adapter boards take care of that for you. The adapter
boards make for a very professional repair. I hate seeing caps hanging
off the board hot glued to something.

If I have to replace one, I generally replace all of them. Then you
won't have to worry about it for 20 years.

By using very long leads on the adapter boards I have replaced the
caps in situ without pulling the main board by threading them down from
the top.

Unsoldering the main caps is fun, not. It's easy to overheat the board
and have trace separation. Be careful and use good desoldering tools
and technique for that. Some chipquick wouldn't hurt.

Paul

On Thu, Dec 24, 2020 at 05:59:34PM +0000, Dave Peterson via groups.io wrote:
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@comcast.net> 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!
--
Paul Amaranth, GCIH | Manchester MI, USA
Aurora Group of Michigan, LLC | Security, Systems & Software
paul@AuroraGrp.Com | Unix/Linux - We don't do windows


Re: Comments from Peter Keller on the 500 Series Scopes

John Atwood
 

Scope Usage at chez Atwood:

Main work bench: 561A with 3A6 or 3A74 and 3B4 plug-ins. I do mainly audio or low HF work here. No fan!

Second bench: 502A - again, mostly audio work. I like the sensitivity and dual beams.

Floating: 485 for RF work.

Audio listening room/bedroom: HP 130C - used for its symmetrical X-Y display (and low cost of acquisition!).

Repair project: 556 in excellent condition, but with a bad tunnel diode. Maybe the best of the 547 and 555? Only 840 Watts max!

Tube testing bench: 570 - Has 45 tubes and only two semiconductors ( 2 x 1N34A)!

Semiconductor test bench: 575

I’ve got a bunch of other scopes lying around waiting for repair or sale/donation: 465s, 2215, 561As, 647, etc.

Tek is great!

- John Atwood WA1ICI/7


Re: tektronix 7S14 batteries and time base question

Rick
 

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


Re: Tek 465 Negative 8 volt rail issues

Dave Peterson
 

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@comcast.net> 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


Re: Comments from Peter Keller on the 500 Series Scopes

Tom Norman
 

My TEK addition started off with a 7904 with a P11 CRT back 25 years ago. The hobby got put on hold, but came back to life about 5 years ago, with another 7904 (this time with P31), about 3 DSA602 variants and a raft of TM500/5000 stuff. About a year ago I decided I didn't know enough about tube circuits and what better way to learn than to pick up a 547. I (foolishly?) drove 800 miles to the recycler in WA to get that scope, and while there, the employee said "oh, by the way, another one just came in. Would you be interested?". I turned the corner and there was a 555 indicator....needless to say, it followed me home. I called it my lonely 555 since it didn't have a power supply, but a couple of fellows from TekScopes came to her rescue and found her a mate, and I found a couple of friends in the process. Next came a 575, and a bunch of plugins for the 500 scopes..... so I've got the "bug"... bad pun intended. (insert TEK "bug" here).

I love the fine trace, my inner mechanical engineer appreciates the mechanical design (my "car" analogy would be something like a 911), and the documentation (and ease of repair) make them a great platform to learn tube tech. All three that I (currently) have I'd call favorites, but the 555 is in my mind pretty special. Where else can you get 8 tiny traces on one CRT (a 556 I suppose) ? :) The 575 brings a lot of utility, but is special to me because it belonged to Charlie Rhodes, and came with a tube curve tracing adapter that he designed and built.

This may be restating Dennis' last point in the initial post, but ease of repair and what I've found to be a pretty extensive "off list" support network contributes to the relative lack of chatter... It's a joy for me to own these scopes and to have repaired them. And the repairing, for me, is particularly satisfying. Along those lines, I wouldn't mind seeing a few (more?) straight up repair reports on tekscopes from time to time.

Dennis and Peter- Thank you for making the books available to us. Can't hardly wait... and Dennis, hope you don't end up sprouting a hernia for your efforts...

Tom


Re: Comments from Peter Keller on the 500 Series Scopes

Don Bitters
 

That sir, is a serious addiction!  Have you considered counseling? (Tongue in cheek!! ;) !!).  I probably have 30+ pieces of ETE, but I am diversified - no more than 5 spectrum analyzers, and 3 O-scopes.Best wishes and a Merry Christmas to you and yours.Don Bitters


Tek 465 Negative 8 volt rail issues

Ed Pavlovic
 

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


Re: Comments from Peter Keller on the 500 Series Scopes

c n
 

My 547 succeeded my first Tek scope, a 545B which I sold to a friend. It has a pristine CRT, that great thin trace which I love and it has been very reliable. I have a 1A1, type Q and and an aftermarket curve tracer plugins for it. I paid the princely sum of $43 for it in the early 90's at the surplus store of a large aircraft manufacturer I worked for here in Seattle before retiring. Unfortunately they no longer retail their surplus. Visible waveforms exceed its calibrated bandwidth considerably. Someone else on this forum has compared the 500 series to a Rolls Royce and I must concur. Unfortunately it is beginning to fall victim to the HV transformer failure and I have yet to decide what course of action to take for a cure.

--
Chuck N.
310A 547 453 475 2430A


Re: Comments from Peter Keller on the 500 Series Scopes

Arne Buck
 

There's a fellow here in Newton MA with an amazing collection of cars,
particularly tiny "Mini and Micro <https://www.bubbledrome.org/index2.html>"
cars, and sponsors a wonderful weekend culminating at the Larz Anderson
Transportation Mvsevm in Brookline MA. Many restored, many more not so,
each category stored in its own warehouse. He is wont to say, "I have this
nightmare in which I've died and my wife sells all my cars for what I told
her I paid for them."


Re: Comments from Peter Keller on the 500 Series Scopes

bobkrassa
 

The number of posts in recent years may not adequately represent the interest in 500 series scopes, because anyone who is aware of this group would search the messages before posting a question and would be very likely to find a comprehensive answer. This group is a tremendous resource!

Also, thanks to Dennis for everything you do!

Bob Krassa AC0JL


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Attilio
 

Thanks tinkera123, I think my 7L13 is similar to yours. My 7L13 has the mechanical indicator for the reference level, but I know the latter had the LED display for the reference level indication.

Greetings and Merry Xmas to all


Looking for pictures of 067-0865-00 calibration fixture for A/P6303 current clamp

Jared Cabot
 

Hi all,

I recently picked up an A6303 (P6303) current clamp and I'd like to construct a calibration fixture to enable me to check and adjust it etc.
It looks just like an aluminium shroud with a hex standoff as a current path through the current clamp jaws, the shroud is connected to the shield on the BNC, the hex stand off connected to the center pin of the BNC via a 50ohm resistor on one side and shorted to the shroud on the other (To form a 50ohm terminated shorting loop).
I found a data sheet for it on the Tek Wiki website, and a picture of the side of it via Google, but I'm hoping someone who might have one can take a few shots from different angles with a ruler for size comparison.
Here is the one photo I have found online so far:
https://i.imgur.com/8zoJDiw.jpg

I'm pretty sure I know how it is constructed, but if I can get a few photos, I'll be able to see for sure.

Thanks!
Thanks!

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