Date   

FS CRT

Paul Koretko
 

Back in January I purchased a "used, good" CRT from one of the reputable
suppliers. Unfortunately I made a big mistake and ordered the wrong
part number. (My Mistake!)

So consequently I have for sale a CRT. TEK #154-0777-00. Used in TEK
465M

If interested please contact me off list. MY CALLS at ARRL dot NET

Thanks for the band width
--
Paul K. WA0BAG


Re: Tektronix 2235A troubleshooting (PSU)

 

My guess is that high ESR in the aluminum electrolytic capacitors is causing
regulation problems. As they warm up, their ESR drops so the regulated voltages
settle closer to where they are suppose to be.

I have seen this happen before (but not on a Tektronix power supply) where the
power supply will start and run once warm but fail to start when cold because of
the difference in ESR.

On Mon, 1 Sep 2014 11:40:14 -0700, you wrote:

Troubleshooting seems pretty straightforward, especially so with instructions manual. Did anyone have same or similar situation? Is there a reason to be concerned - I've read that high frequency sound might be caused by high ESR caps or magnetics under saturation? My ESR meter goes down to 1uF and all caps that are above that read fine. I would like to hear some opinions first before starting to desolder. Especially so, because I don't have any experiences with this model of oscilloscope (maybe this is a known fault?).


Re: Tektronix 2235A troubleshooting (PSU)

Ted Rook
 

Congratulations!

The circuit in my similar 2213A has one -8.6V adjuster for the whole system. Your DC
voltages are very close to specification so there does not seem to be a major problem, this is
good news :-)

According to the Tek manual when you adjust the -8.6V supply you must then recalibrate the
entire scope. I wonder if this is necessary, the DC figures you have are very close to normal
already, perhaps it is better to hold back?

In my 2213A there is a small area beneath the tube where the vertical drive circuit is located
and it is discolored, there is a set of six identical resistors that get hot, but I don't suspect a
fault, I have read that this is common with some models in this series of scopes.

Ted


On 1 Sep 2014 at 11:40, Ante Marin ante.marin@... [TekScopes[TekScopes]
Tektronix 2235A troubleshooting (PSU) wrote:



Hi all,

recently I got my first scope, Tek 2235A, from Ebay for 125EUR +
shipping. Lightweight, rugged,
relatively young ('91 vintage), easy to fix and service, no
unobtanium parts plus this particular one
was advertised as 'in good working condition'.

And indeed, it works fine. Most important to me is that CRT is in
good condition. Focuses nicely
and trace is bright.

However,

#1 Unit produces audible, high frequency sound when starting. It's
not loud and does not vary in
frequency. After scope warms up, the sound disappears (see #2).

#2 I checked voltages; -8.6V, +8.6V, +5.2V, +30V and +102V.
Just after start-up, these read: -8.87V, +8.94, +5.51, +30.82 and
+105.2.
So, over-voltage on all lines except +30V, which is close to upper
threshold.

After 20-30 min of warming up these read: -8.67V, +8.74V, +5.39V,
+30.26V and +102.7V.
This looks much better, with +5V and -8.6V line being out of
limits.

The readings were obtained with intensity knob being slightly under
mid point. There is a pot for
-8.6V adjustment, don't know if this will affect other (low)
voltages but I suspect root of problem is
somewhere else (see #3).

#3 PCB underneath Q944, R943 (PSU), CR960/61/63 (high voltage PS)
and Q256/257,R256/257
(vertical output amp) is discolored (but not burnt). Overheating
obviously, but not affecting scope
operation (and vertical seems to be in calibration). The unit does
not have a fan, but I don't think
this would cause PCB discoloration.

Troubleshooting seems pretty straightforward, especially so with
instructions manual. Did anyone
have same or similar situation? Is there a reason to be concerned -
I've read that high frequency
sound might be caused by high ESR caps or magnetics under
saturation? My ESR meter goes
down to 1uF and all caps that are above that read fine. I would like
to hear some opinions first
before starting to desolder. Especially so, because I don't have any
experiences with this model of
oscilloscope (maybe this is a known fault?).

Br,
Ante




Re: Hello from new member

Ante Marin
 

Hi Richard,

I've created another thread, 'Tektronix 2235A troubleshooting (PSU)'. You can check it out, will be appreciated.

Br,
Ante

---In TekScopes@..., <mechanic_2@...> wrote :

Hello Ante,
Welcome! So what is wrong with your scope?
rich!


Tektronix 2235A troubleshooting (PSU)

Ante Marin
 

Hi all,

recently I got my first scope, Tek 2235A, from Ebay for 125EUR + shipping. Lightweight, rugged, relatively young ('91 vintage), easy to fix and service, no unobtanium parts plus this particular one was advertised as 'in good working condition'.

And indeed, it works fine. Most important to me is that CRT is in good condition. Focuses nicely and trace is bright.


However,

#1 Unit produces audible, high frequency sound when starting. It's not loud and does not vary in frequency. After scope warms up, the sound disappears (see #2).


#2 I checked voltages; -8.6V, +8.6V, +5.2V, +30V and +102V.
Just after start-up, these read: -8.87V, +8.94, +5.51, +30.82 and +105.2.
So, over-voltage on all lines except +30V, which is close to upper threshold.

After 20-30 min of warming up these read: -8.67V, +8.74V, +5.39V, +30.26V and +102.7V.
This looks much better, with +5V and -8.6V line being out of limits.

The readings were obtained with intensity knob being slightly under mid point. There is a pot for -8.6V adjustment, don't know if this will affect other (low) voltages but I suspect root of problem is somewhere else (see #3).

#3 PCB underneath Q944, R943 (PSU), CR960/61/63 (high voltage PS) and Q256/257,R256/257 (vertical output amp) is discolored (but not burnt). Overheating obviously, but not affecting scope operation (and vertical seems to be in calibration). The unit does not have a fan, but I don't think this would cause PCB discoloration.


Troubleshooting seems pretty straightforward, especially so with instructions manual. Did anyone have same or similar situation? Is there a reason to be concerned - I've read that high frequency sound might be caused by high ESR caps or magnetics under saturation? My ESR meter goes down to 1uF and all caps that are above that read fine. I would like to hear some opinions first before starting to desolder. Especially so, because I don't have any experiences with this model of oscilloscope (maybe this is a known fault?).


Br,
Ante


Re: Weird cursor problem on 2465 scope

 

Doing a little more diagnostics, I measured the the voltage at pin 5 of U2435B and
as I turn the knob, it cleanly changes voltage (from negative through positive voltages)
through the "stuck" area and keeps going. So the problem is neither in the DAC nor
the analog multiplexer.

When I measure the voltage at the output, i.e. pin 7, it starts off negative, tunes down
to approximately -0.39 volts to the wall, then as the cursor gets stuck it instantly leaps
to +14v. So the output of the opamp doesn't have a problem swinging both above and
below ground.

Trying to think these symptoms could be a problem with one of the diodes, CR2744
or CR2742. They would certainly be easier to change out than the TL074.

Scott

On 8/27/2014 11:56 AM, siggi@... [TekScopes] wrote:
There's also U2800 & U2805 on the readout board, who do analog multiplexing between cursors and character positioning.
Incidentally, it looks like the DLY REFs also control the delay trigger times. You should be able to see whether the fault is on A5 or the readout board by setting up a dual delay B-sweep, and see whether both delays have the same control range.
If one of the delays is constrained, then you're looking at something on the A5 board.






------------------------------------
Posted by: siggi@...
------------------------------------


------------------------------------

Yahoo Groups Links



---
This email is free from viruses and malware because avast! Antivirus protection is active.
http://www.avast.com


Re: Tek 310 HV transformer

ken chalfant
 

Greetings,

FWIW there is a Tek 310A listed on US eBay for USD 99.99 MAKE OFFER (for parts - not working).

eBay listing: 361028581762

It is located in Lansdale, Pennsylvania USA but the listing indicates they will ship anywhere.

Might be worth some investigation - after all it could be a lifetime supply of spares.

I owned a Tek 321A that I used for years on big SCR drives because it could be operated from "D" cells (lots of "D" cells) and I really loved it! Ultimately I replaced it with a handheld DSO.

I hope you succeed in restoring your 310A.

Best of luck!

Ken (USA)

On 1Sep, 2014, at 11:41 AM, Manfred Mornhinweg manfred@... [TekScopes] wrote:

Hi all!

I'm Manfred, from Chile, and I'm new to this group (but not new to oscilloscopes!).

Recently I was given a Tek 310 scope. It's in pretty good cosmetic condition,
but missing a few parts. I suspect it was used as a donor to restore another
one, after suffering some major fault.

I would like to restore it to working condition.

The most critical of the missing parts is the HV transformer. I do have a good
selection of ferrite cores on hand, and I have quite some experience designing
and winding transformers - but I don't know much about this specific
transformer! Only what I can find out from the schematic and description in the
manual. So I'm looking for any help that would allow me to design and wind a
usable replacement transformer.

If anyone in the group happens to have full specs of the transformer, that would
be of course the best help I can hope to get. But lacking that, I would get some
big steps ahead if somebody who has a functioning 310 could provide me the
following information:

- Dimensions of the ferrite core, including air gap width, if any.

- Oscillograms of the voltages on each side of the tapped primary winding;
Either as photos with indication of scaling values, or as a description (wave
shape, peak-to-peak voltage, frequency).

- Resistance of each winding.

- Inductance of each winding would be great, but probably few people have the
means to measure it. It would probably require disconnecting some wires, which
is likely too much to ask.

- If the transformer uses any particular construction technique, detailed photos
of it would be useful. The photos I have seen so far are too blurry to be of
much use.

- Any other information that would seem useful.

The most important among these would be the oscillograms, because they would
allow me to know whether this oscillator works in resonant mode, or in blocking
mode controlled by core saturation. And they would give me the ratio of turns
between the sides of the primary, which is a big question I have right now. And
it would tell me at which amplitude the oscillator works.

I think I can work out a design and build it, if I get that data. Without that
data, it would probably take me several attempts.

The other parts missing are far less critical: The scale illumination
potentiometer and its knob, the fuse holder, power input connector, a few of the
tubes (for which I have workable replacements), and some resistors and
capacitors in the HV section.

What I can offer to the group: My main daily use scope is a D755, which I got in
dead condition in 1988, and repaired. I have kept it alive since then, so I know
it reasonably well.

Manfred

========================
Visit my hobby homepage!
http://ludens.cl
========================


Tek 310 HV transformer

Manfred Mornhinweg
 

Hi all!

I'm Manfred, from Chile, and I'm new to this group (but not new to oscilloscopes!).

Recently I was given a Tek 310 scope. It's in pretty good cosmetic condition, but missing a few parts. I suspect it was used as a donor to restore another one, after suffering some major fault.

I would like to restore it to working condition.

The most critical of the missing parts is the HV transformer. I do have a good selection of ferrite cores on hand, and I have quite some experience designing and winding transformers - but I don't know much about this specific transformer! Only what I can find out from the schematic and description in the manual. So I'm looking for any help that would allow me to design and wind a usable replacement transformer.

If anyone in the group happens to have full specs of the transformer, that would be of course the best help I can hope to get. But lacking that, I would get some big steps ahead if somebody who has a functioning 310 could provide me the following information:

- Dimensions of the ferrite core, including air gap width, if any.

- Oscillograms of the voltages on each side of the tapped primary winding; Either as photos with indication of scaling values, or as a description (wave shape, peak-to-peak voltage, frequency).

- Resistance of each winding.

- Inductance of each winding would be great, but probably few people have the means to measure it. It would probably require disconnecting some wires, which is likely too much to ask.

- If the transformer uses any particular construction technique, detailed photos of it would be useful. The photos I have seen so far are too blurry to be of much use.

- Any other information that would seem useful.

The most important among these would be the oscillograms, because they would allow me to know whether this oscillator works in resonant mode, or in blocking mode controlled by core saturation. And they would give me the ratio of turns between the sides of the primary, which is a big question I have right now. And it would tell me at which amplitude the oscillator works.

I think I can work out a design and build it, if I get that data. Without that data, it would probably take me several attempts.


The other parts missing are far less critical: The scale illumination potentiometer and its knob, the fuse holder, power input connector, a few of the tubes (for which I have workable replacements), and some resistors and capacitors in the HV section.

What I can offer to the group: My main daily use scope is a D755, which I got in dead condition in 1988, and repaired. I have kept it alive since then, so I know it reasonably well.

Manfred


========================
Visit my hobby homepage!
http://ludens.cl
========================


Re: 2465 Sweep Problem

 

I think you are right about the voltage levels. If U910B is correcting the Vbe
of the integration current source which is typical in these designs, then the
voltage change is going to be small to produce a sweep error of only 33%.

The TL072 is not what I would consider a precision operational amplifier but it
does have low input bias current and the precision level needed over temperature
is only within line 1%.

On 31 Aug 2014 19:04:44 -0700, you wrote:

After swapping the A and B sweep hybrids, many hours of taking measurements, and a lot of head scratching the problem turned out to be a .47 uF cap, C712 in the A sweep circuit. It was leaky to the tune of ~8K ohm. What surprised me most was that after the cap fixed the problem, the voltages on U910B changed only slightly. I suppose this must be because U910B is in the heart of the current mirror and the small current leakage through C712 had a large effect on the currents in the circuit but in this case the voltages just didn't show much.


585A for sale in UK.

Geoff Blake <geoff@...>
 

(Posted OBO a friend, The 'scope is in Basildon.

Due to a renovation in the front room area and lack of space, I have to
sell my tektronics 585A scope. No scope probes, as they are cheap enough
anyway, but has the type 82 plugin unit and its original manual. The scope
is in working order and I have attempted a clean , but removing the dist
around the valves, and other areas I can reach. Still needs more cleaning
Both traces are in focus and there a 15mm horizontal scoring line on the
crt display on the inside left, but could be a burn mark. Otherwise its
looks okay.
Also, the one side cover fasters are missing. Its a boat anchor job but a
good olde workhorse.

If there is any interest, contact me initially and I will forward.

Geoff

#################################################
Geoff Blake, G8GNZ JO01fq: Chelmsford, Essex, UK
<geoff@...> or <melecerties@...>
Using Linux: Ubuntu 11.04 on Intel or Debian on UltraSparc
and Apple OS X 10.8.2 Mountain Lion on my Macbook Pro.
Avoiding Micro$oft like the plague.
#################################################


Re: 2465 Sweep Problem

 

Thank you Craig, very interesting !

Matthias

Am 01.09.2014 04:04, schrieb craigyard99@... [TekScopes]:



After swapping the A and B sweep hybrids, many hours of taking
measurements, and a lot of head scratching the problem turned out to
be a .47 uF cap, C712 in the A sweep circuit. It was leaky to the tune
of ~8K ohm.

I appreciate the knowledge I have picked up from this group, perhaps
this will help someone else with a similar issue.


Craig


Re: 465->2465 General Information

 

The 2440 series which includes the 2430, 2430A, 2431L, 2432, 2432A, and 2440 are
digital storage oscilloscopes with real time operation and automatic
measurements. Someone used to modern DSOs would recognize them as DSOs and they
are very capable even compared to many modern instruments.

I do not think Tektronix could have included 4 channels in a DSO of that size at
that time and they are not small. They are packed full of circuitry.

They do have two full bandwidth external trigger inputs and some interesting
trigger modes to go with them but I am not sure what application Tektronix had
in mind.

On Mon, 1 Sep 2014 10:47:34 +0100, you wrote:

...and I have just come across the 2430 and 2440 which have 2 channels...


Re: Making a safe 1KV source!

hpxref
 

<You can buy an electrophoresis supply for $50, some
<will do 500V, some 2,000.
<High voltage supplies -- don't try this with an ordinary
<transformer as the insulation will break down -- for most
<tube equipment over 600V and you are past the margin of
<safe

A good approach. The one I had included 2 fully independent 2kV supplies in the same
box controlled by 10 turn pots. Could series them up for 4Kv with no problems provided you
awitched each to the same output (CV or CI or CP)
Both used regulated oscilators/rectifiers using ferrite cores. Nicely made unit
Also had a Philips fully adjustable to 1 kv HV supply intended for Prop or scint counters ...vary stable
The newer models used mag amps as the control elements..older one I had
used tube HV oscillator with Vout regulation by varying screen volts
Both PW numbers
Some times the Philips PW series sell cheaply as few know what they are .
I got mine for $5

John


Re: 465->2465 General Information

Mike Malone
 

...and I have just come across the 2430 and 2440 which have 2 channels...


File - Posting Rules

TekScopes@...
 

Welcome to TekScopes. If you're a new member, please introduce yourself to the group. Tell us your interests. Regale us with your Tek stories and collection.

Please edit replies to the list to reduce quoted material only to that required for continuity.

PLEASE do not send personal replies to the list. As replies go to the list by default, modify the recipient address when necessary.

If you are having difficulty with the Yahoo site, please try a different or more recent browser. Also, changes to your email address or settings are your responsibility. We realize the Yahoogroups interface may not be the most intuitive thing on the planet, but we're sure you can figure it out. There are too many variables, given different browsers & OSes, for us to offer assistance.

Those congesting the list with with personal email or excess quoting may have posting rights revoked. Only by following these simple rules will we have a "clean" archive. They also reduce inbox clutter, make digests much nicer to read, improve searches, and reduce the chance of having old messages deleted.

To post to the group, mail to:

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Remember that the two archive groups have more files beyond what's here.

If you do not wish to belong to TekScopes, you may
unsubscribe by sending an email to

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You may also visit the Yahoo web site to modify your
subscription:

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Check out the files, links, and photos sections,
and remember, you can search the group's archives from its home page,
or when reading messages. The group's home is at:

http://groups.yahoo.com/group/TekScopes

Regards,
Michael Dunn
Listowner, TekScopes


Re: Replacement rear feet for 465B?

lemonscentedmoisttowelette@...
 

I am not sure if my email address came through or not...

It is:
First Part LemonScentedMoistTowelette
Next Part (AT) symbol
Last Part cox.net


Thanks,
Benny McClain


Re: Replacement rear feet for 465B?

lemonscentedmoisttowelette@...
 

Hello,

I was making 3D printed feet and handle caps for Yahoo Group members and the eBay community in 2012 and 2013. The demand was pretty steady at first, but then dropped off. I figured everyone that needed them found them and I got side-tracked on other projects. Anyway, I still have my design files and 3D printer, so I can make more feet for anyone that needs them.


The rear feet fit the Tektronix 465, 465B, 466, 468, 475 and 475A Oscilloscopes. They are made using ABS plastic. The result is a high quality and strong replacement part that matches the original design. ABS plastic is more rigid than the original material used for these feet. I've taken that into consideration with my design, ensuring the power cord still "snaps" into place as it is wrapped around the feet.


I sold over 200 feet and received lots of positive feedback. If you search for "3D printed" in the pictures section of this forum, you can see images of the feet and the handle caps I created.


I've priced the feet at $5 per foot, plus $6 for Priority Mail shipping. International orders will cost more for shipping.



Benny McClain


My email address is below. I am breaking it up in order to prevent it from being harvested...


First part is
LemonScentedMoistTowelette
The second part is
@cox.net


Re: Making a safe 1KV source!

Dave Seiter
 

I think Jim's bench is still at the Computer History Museum in Mountain View (Ca). Never been, even though it's only a few minutes away.

-Dave


________________________________
From: "Irvin Schwartz sl45000@... [TekScopes]" <TekScopes@...>
To: TekScopes@...
Cc: ROBERTBARKER@...
Sent: Saturday, August 30, 2014 8:17 PM
Subject: Re: [TekScopes]Making a safe 1KV source!




--------------------------------------------
On Sat, 8/30/14, jdwalton@... [TekScopes] <TekScopes@...> wrote:

Subject: Re: [TekScopes]Making a safe 1KV source!
To: TekScopes@...
Date: Saturday, August 30, 2014, 7:42 AM


REMEMBERING JIM WILLIAMS..... WE MISS HIM

WHERE IS HIS "BENCH' NOW ??

...BOB...

You can buy an electrophoresis supply for $50, some
will do 500V, some 2,000.
High voltage supplies -- don't try this with an ordinary
transformer as the insulation will break down -- for most
tube equipment over 600V and you are past the margin of
safe

Some resistors have a DC resistance coefficient -- best off
with resistors made for the purpose or place several in
series.

A must read by the late Jim Williams:

http://cds.linear.com/docs/en/application-note/an118fa.pdf



https://www.youtube.com/watch?v=e9RX_UPownc



Low Noise, High Voltage DC/DC Converters - Linear...
https://www.youtube.com/watch?v=e9RX_UPownc with Jim
Williams, Staff Scientist



[Non-text portions of this message have been removed]


2465 Sweep Problem

Craig
 

Had a challenging 2465 failure that may interest the group. This was on a 2465 I picked up on ebay a couple of weeks ago (you may remember the one with the bent knobs). Other than several bent potentiometer shafts the instrument was in good physical condition and very clean internally.


After repairing the pots and recapping the LV power supply (thank you maxx6668 for the spot-on list of caps to buy), the instrument turned on normally and did not display any error codes. Upon further checking, I found that the sweep cal was off by about 33% (100uS markers read 67uS). This cal error was very consistent across all horizontal time settings.


When I attempted to run the cal 01program, the marker alignments in both step 2 and step 3 did not have enough adjustment range to complete the alignment. Out of range messages were displayed on the CRT when the end of the adjustment range was reached.


After swapping the A and B sweep hybrids, many hours of taking measurements, and a lot of head scratching the problem turned out to be a .47 uF cap, C712 in the A sweep circuit. It was leaky to the tune of ~8K ohm. What surprised me most was that after the cap fixed the problem, the voltages on U910B changed only slightly. I suppose this must be because U910B is in the heart of the current mirror and the small current leakage through C712 had a large effect on the currents in the circuit but in this case the voltages just didn't show much.



I appreciate the knowledge I have picked up from this group, perhaps this will help someone else with a similar issue.


Craig


Re: 465->2465 General Information

 

AFAIK, the 465M borrows heavily from the 455 and as such I wouldn't be tempted to call it a Hi-Rel or ruggedized 465-like 'scope. I think this has been discussed a while ago on this forum as well. Maybe the 465M just inherited the 455's trigger circuit? I haven't checked schematics though. I'm not at all familiar with MilSpec etc, so I can't correctly interpret the 465M's description in the Tek catalog.
I was unaware of the connection between the 465M and the 455 until recently. I
have since updated my notes to place the 465M with the 455 as a separate group.

I think your assumption that the 475(A) and 485 have always been equipped with tunnel diode trigger circuits is correct.
I think this makes sense from a performance point of view. My guess is that
Tektronix did not have a 200+ MHz integrated trigger until the 7B80, 7B85, and
7B92A which was sometime after the 475 and 485 were introduced. I do not have
exact dates on those because I have not gotten that far through the catalogs. :)

The 468 uses an IC trigger circuit.
So it does. Thanks for pointing this out.

Somehow when I originally checked the schematics, I decided that the 468 used
tunnel diodes. Now I am not sure how it is related to the others. I has the
integrated trigger of the 464 and 466 but the fast sweep and introduction date
of the 465B.

From what I see on the most popular Dutch used-equipment sites, there's about one 465B on offer for every 465.

Sorry, made a typo:

"From what I see on the most popular Dutch used-equipment sites, there's about one 465B on offer for every THREE 465's."
This is why I do not anticipate getting one of these oscilloscopes. On one
hand, I am not fond of mixed sweep. On the other hand, the 465B, 468, and 485
are the only ones with alternate sweep. On the gripping hand, those are either
complicated or rare.

If one falls into my hands I will repair it but in the meantime I have my 2230.