Date   
TEK PS 2521

Michael Yellin
 

Hello,

Recently acquired a Tek 2521G, which appears to be in great shape. Inspected the inside, and nothing jumps off and the caps looks fine. However, whenever a load is placed on any of the outputs, the voltage drops. With no load, the voltage is accurate as set, and when a load is placed, the amperage is dead on for the setting. But, as mentioned, as soon as a load is placed on any of the outputs, the voltage for that output drops significantly. I have run through the calibration, with out fixing the unit. I plan to do the complete calibration shortly (all outputs in order), but am beginning to think it is not a calibration issue. Can anyone think of what might cause all the outputs to act exactly the same. My understanding is that the unit essentially is three separate "boards" so I find it strange that all three outputs are behaving the same. I have some basic repair skills, and a fair compliment of test equipment. Any help would be greatly appreciated.

Thanks,
Michael

Re: Tek 1503 in this group's bailiwick? Not exactly a scope...

Harvey White
 

As far as I remember there are two supplies, the LV and the HV. I know the HV has a transformer and seems to run hot (I've seen somewhat cooked boards).  The HV multiplier is made of discrete parts, and can be replace individually.  IIRC, some microwave oven diodes seem to be a good fit.

You can replace the NICD battery by a DC supply of the appropriate voltage for testing purposes, but the original design needs the battery in there for filtering purposes.

Harvey

On 11/12/2019 3:53 PM, Chuck Harris wrote:
Also, unless they are modified, they will NOT work if the
nicad battery is dead.

-Chuck Harris

Tom Gardner wrote:
Yes, it is.

I suggest you use the groups.io web interface, and search for 1502 and 1503. IIRC
they are contemporary and have similar PSUs. OTOH B and C variants have different PSUs.

But you would be wise to check that!


On 12/11/19 20:03, george gonzalez wrote:
Is the Tek 1503 in this group's bailiwick? Not exactly a scope…

It seems to have “issues”. The switching power supply is squeezing more than
switching.


Re: The best laid plans of mice and men....

Reginald Beardsley
 

Well, it turns out that one *is* defective. It's missing the retainer for the rear connector. and one channel selection button was broken. So I glued that.

I've got a mill, so I could make one, but it's not really set up for use. So if anyone has a spare clamp for retaining the rear connector and the 3 screws, please email me. And a complete, *non-working* SD series head would be even better. Especially an SD-24.

I bought a $50 HP 16500A with 1x 16532A & 4x 16550A. It arrived non-functioning, but a few hours and I had everything working. I put the 16532A in my 16500C, but that left me with the 4x 16550As. So I decided I needed a 16501A to hold them. God only knows whether I'll ever need that many channels.

Reg

Re: Tek 1503 in this group's bailiwick? Not exactly a scope...

ArtekManuals
 

George

By "squeezing" I am going to guess you mean "ticking" a common symptom of a switching power supply going in to protection mode because there is high current drain. Typically this is caused by shorted bypass capacitors usually tantalums on a DC bus somewhere but shorted transistors and IC's are usually right behind the caps as likely suspects

Dont know the history of the name, maybe because oscilloscopes was/is Tektronix strong suit. At any rate in general anything designed and manufactured by Tektronix has traditionally been discussed on here.

As another poster suggested go to the group web site and do a search. The one flaw with that approach is netiquette is not the strong suit of the group membership. Threads are often hijacked and you will find the contents of some of the messages with 1503 in the subject line have absolutely nothing to do with the 1503 . Other threads with info about the 1503 have nothing in the subject line because they in turn were hijacked threads from another topic.

If it were me I would do a search in the group archives first, if you dont find the solution to your problem then come back here with as much detail about what your problem looks like and I am sure we will try and help you

Cheers
and good luck

Dave
manuals@...

On 11/12/2019 3:03 PM, george gonzalez wrote:
Is the Tek 1503 in this group's bailiwick? Not exactly a scope…

It seems to have “issues”. The switching power supply is squeezing more than switching.

Thanks,

George

AG0I


--
Dave
Manuals@...
www.ArtekManuals.com

Re: The best laid plans of mice and men....

John Ferguson
 

I well know the frustration of buying a "parts-only" scope only to have it show up working and not even that far out of cal - if out at all.  Still need a carrying handle for my 2445B.

john

On 11/12/19 2:45 PM, Reginald Beardsley via Groups.Io wrote:
I bought a cheap pair of SD-22s listed as "defective" on ebay so I had a sampling head I was willing to open up and examine and perhaps use the case to test a DIY version.

They arrived today. Both work fine. So now I have 4x SD-22, 4x SD-26 and 1x SD-24 all of which work and am still looking for a carcass to play with.

Oh, well...
Reg

Re: Tek 1503 in this group's bailiwick? Not exactly a scope...

Chuck Harris
 

Also, unless they are modified, they will NOT work if the
nicad battery is dead.

-Chuck Harris

Tom Gardner wrote:

Yes, it is.

I suggest you use the groups.io web interface, and search for 1502 and 1503. IIRC
they are contemporary and have similar PSUs. OTOH B and C variants have different PSUs.

But you would be wise to check that!


On 12/11/19 20:03, george gonzalez wrote:
Is the Tek 1503 in this group's bailiwick? Not exactly a scope…

It seems to have “issues”. The switching power supply is squeezing more than
switching.


Re: Tek 1503 in this group's bailiwick? Not exactly a scope...

Tom Gardner
 

Yes, it is.

I suggest you use the groups.io web interface, and search for 1502 and 1503. IIRC they are contemporary and have similar PSUs. OTOH B and C variants have different PSUs.

But you would be wise to check that!

On 12/11/19 20:03, george gonzalez wrote:
Is the Tek 1503 in this group's bailiwick? Not exactly a scope…

It seems to have “issues”. The switching power supply is squeezing more than switching.

Tek 1503 in this group's bailiwick? Not exactly a scope...

george gonzalez <grg2gonzalez@...>
 

Is the Tek 1503 in this group's bailiwick? Not exactly a scope…

It seems to have “issues”. The switching power supply is squeezing more than switching.

Thanks,

George

AG0I

Re: Trace jitter

Clark Foley
 

One unexpected source of jitter on the 11800 series is the timebase delay/position setting. The horizontal position is not phase locked to anything. As such, long delay times (e.g. greater than 1us) result in a wondering trace, horizontally. Verify that the horizontal position is very small, on the order of 10's of nanoseconds before messing with the hardware. The 11800 series gives great results for short delay times but not as you approach 1us.

The best laid plans of mice and men....

Reginald Beardsley
 

I bought a cheap pair of SD-22s listed as "defective" on ebay so I had a sampling head I was willing to open up and examine and perhaps use the case to test a DIY version.

They arrived today. Both work fine. So now I have 4x SD-22, 4x SD-26 and 1x SD-24 all of which work and am still looking for a carcass to play with.

Oh, well...
Reg

Re: National Instruments GPIB-400

Arie de Muijnck
 

For interested people, these links offer them:
https://www.aliexpress.com/item/4000307544118.html This seems the original (hobbyist) manufacturer,
https://www.aliexpress.com/item/4000017713738.html
https://www.aliexpress.com/item/33019224024.html Where I bought mine, not the original mfg.

Re: National Instruments GPIB-400

Arie de Muijnck
 

On 2019-10-02 23:12, Arie de Muijnck wrote:
Thanks for that AR488 info, that looks really good.
I was searching for a low cost USB-GPIB adapter.

BTW, did anyone ever buy this (looks new on aliexpress),
it's a compact open source Prologic compatible for about $20:
https://www.aliexpress.com/item/4000034884174.html
The open source is here:
https://github.com/fenrir-naru/gpib-usbcdc

Regards,
Arie de Muijnck
Well, I bought one for about EUR 18 including shipping, it finally arrived - and works!
It shows up as a COM port, and uses a Prologix compatible communication protocol.

Checked using Teraterm, on 460 kBd: OK.
It is recognized by eg. the GPIB configurator from John Miles, ww.ke5fx.com.
Tested it on my HP (sorry...) 54645D scope: OK.
Now I'll just have to find (or write) software to grab and process those deep 1Ms buffers...

Arie de Muijnck

Re: vintageTEK scanned transformer drawings for 120-0998-01 and up

Dave Brown
 

Both files have been updated with 25 new scans. I received some of the missing scans from another individual with microfiche and incorporated them into the files. The links are the same. - Dave

Re: 577 D1 storage & brightness control

Mlynch001
 

Sorry, yhinking of "Peter Bunge" and his looping from another Type 576 post. . . . Good luck Siggi with your 577, wonderful that it followed you home. You will certainly enjoy using it.

--
Michael Lynch
Dardanelle, AR

Re: 577 D1 storage & brightness control

Mlynch001
 

Dennis,

I have both the 576 and 577 and when I first started using the 577, I thought that it had died or had some other defect when I first noticed that "dimming dot" phenomenon. I wish the engineers on the 576 had been so perceptive and included this feature in that machine as well. Both machines are incredible in their own right. I converted my 577 D2 over to a D1 for the reason that you are explaining in your previous posts. I keep learning more every day while using these instruments. One thing that I found interesting is observing the trace of a tunnel diode. Seeing things visually makes all the difference in the world to me when it comes to understanding what is going on in a component. I appreciate your comments and learn something new from almost every one of them. I hope Peter can get his 576 in top condition.

--
Michael Lynch
Dardanelle, AR

Re: 577 D1 storage & brightness control

Siggi
 

On Tue, Nov 12, 2019 at 9:11 AM Dennis Tillman W7PF <@Dennis_Tillman_W7pF>
wrote:

Hi Siggi,
Congratulations! You have found an excellent curve tracer.
There is a circuit in all 577s to prevent the CRT from being burned when
you turn the collector voltage down so low that it essentially becomes a
dot on the lower left corner of the screen when you are testing NPN
transistors or on the upper right corner when testing PNP transistors. That
bright spot would eventually burn the phosphor at that spot.
Hey Denis thanks for the reply.
I hadn't realized that the collector supply would affect the intensity as
well, but I can see it now in the schematic. I'll have to look for that
when I dig in.


The brightness control should work regardless of how long the collector
voltage trace looks like when it is sweeping across the screen. You should
be able to adjust the brightness when the beam is anywhere.
The only time the trace is automatically dimmed is when the trace is
reduced to the size of a dot or when it is so very short that it might burn
the phosphor.
Right, thanks.
BTW: Nothing like reading the manual - on page 2-3 of the service manual
<http://bama.edebris.com/download/tek/577-177-d1/070-1414-00_Tektronix_577_Curve_Tracer_Service_Feb88.pdf>
it says:

BRIGHNESS
Provides continuously variable flood-gun current duty cycle from about 10%
to 100% (when the collector sweep is turned down or disabled), permitting
extended retention of displayed information. Also controls the degree of
spot dimming when collector sweep is turned down or disabled.

And on the schematics I see that the intensity modulation and the flood gun
current duty cycle are indeed tied together. It all makes sense now.

Re: 2465 Fan Collet Thingy

Siggi
 

On Mon, Nov 11, 2019 at 9:00 PM n4buq <n4buq@...> wrote:

Being a little picky, but the other end of that stud is 40 t.p.i. so an
even finer pitch (#4-40 on one end and #8-32 on the other).
So it is, thanks for the correction.

Re: Tek 576 noise and looping

peter bunge
 

Yes, I have trouble even finding my own postings. I searched on "tek 576
repair log" and got it right away.
https://groups.io/g/TekScopes/files/Tek%20576%20Curve%20Tracer%20Repair/Tek%20576%20Curve%20Tracer%20repair%20Log%201.pdf

I have uploaded several repair logs packed with useful information but
obviously no one has been able to find them. I include the name of the
instrument (HP 8566A) in the title so they should not be too difficult to
find.
I just searched on my "HP 8566A Repair Log.pdf" and realized I did not
upload it because it has photos and ideas from other people that are not
credited. These are my notes that include any source I can find and were
never intended for general distribution. What is the policy? I can send
them privately.
That's a good idea to include the URL when referencing them but it does not
help next month when someone is having the same problem.
Peter.

On Tue, Nov 12, 2019 at 9:23 AM Dennis Tillman W7PF <@Dennis_Tillman_W7pF>
wrote:

Hi Peter,
TekScopes couldn't find your photos when I asked it to search on the file
name you gave. It took me 8 or 9 search queries before TekScopes finally
found it.
In the future it would be very helpful to include the actual URL in
addition to the name of the file so people could immediately see what you
need help with.
Dennis Tillman W7PF

-----Original Message-----
From: peter bunge
Sent: Monday, November 11, 2019 12:58 PM

I suspected that I could not attach photos.
Any one interested please see the file I uploaded with examples of looping
on pages 5 and 6.
File is: Tektronix 576 Curve Tracer Repair Log 1.pdf
It also covers several repairs and my current attempt to find out about
the noise.
PeterB

On Mon, Nov 11, 2019 at 12:19 PM Mlynch001 <@mlynch001> wrote:

"I'm not sure if pictures show up, let me know.
[image: 2N3568 low current.jpg]"

Peter,

Attachments are not allowed within our posts. However, you can post
your
picture(s) in the "PHOTOS" section. Make a File and share the
filename in a post. Then anyone can see the photos. Please edit and
reduce the size of the files to save our limited storage space on the
forum.

--
Michael Lynch
Dardanelle, AR







--
Dennis Tillman W7PF
TekScopes Moderator



Re: Tek 576 noise and looping

 

Hi Peter,
The looping compensation will help somewhat. See my previous email for what causes the loops and how to remove them.

Dennis Tillman W7PF

-----Original Message-----
From: peter bunge
Sent: Monday, November 11, 2019 6:52 PM

Kevin; I found the looping capacitor broken probably from dropping the 576 during shipping. I repaired it with epoxy and used a different shaft coupling that can be seen in a photo in my notes. Have you looked at them?
Why do you ask? It does nothing to the noise or looping I'm seeing. I have the parts unit working, with the help of epoxy, so I can compare both units. I will try to get thru the adjustments to the noise check on the parts unit and see if there is a difference.
Peter.

On Mon, Nov 11, 2019 at 5:53 PM Kevin Oconnor <@KO3Y> wrote:

Peter,
I had forgot about that looping compensation capacitor Ed mentioned.
Do look into it since it sounds like you are digging inside. Let us
know what you fine.
KJO KO3Y







--
Dennis Tillman W7PF
TekScopes Moderator

Re: Tek 576 noise and looping

 

Hi Peter,
The big loops in one photo, which is showing a worst case scenario, are due to the Miller Effect which takes the very small capacitance (Ccb) between the collector and base and multiplies it by the gain of the transistor (Beta).
As a result the sweeping collector voltage (dV/dt) generates current loops (Ib) because a tiny capacitance is multiplied by a factor of 100 and shows up as loops in the base steps. Ib = Beta x Ccb x (dV/dt).

The solution is to shut off the collector sweep and switch to the DC position which supplies a fixed voltage to the collector. Now by manually sweeping the DC slowly from 0V to your maximum voltage you will eliminate the loops. Of course on a 576 all you see is a dot which, as you slowly turn the collector voltage up, the dot will move. With a grease pencil (or equivalent) mark the progress of the trace as you increase the collector voltage and you will get a sort of useful set of curves.

A MUCH SIMPLER SOLUTION is to get a 577-D1 (Storage version). All you have to do is turn the storage on and slowly increase the DC collector voltage and the screen stores the resulting curves without loops as you increase the DC collector current slowly. This is just one of the many things you can do with the 577-D1 storage that you can't do with any other curve tracer.

Dennis Tillman W7PF

-----Original Message-----
From: peter bunge
Sent: Monday, November 11, 2019 12:58 PM

I suspected that I could not attach photos.
Any one interested please see the file I uploaded with examples of looping on pages 5 and 6.
File is: Tektronix 576 Curve Tracer Repair Log 1.pdf
It also covers several repairs and my current attempt to find out about the noise.
PeterB

On Mon, Nov 11, 2019 at 12:19 PM Mlynch001 <@mlynch001> wrote:

"I'm not sure if pictures show up, let me know.
[image: 2N3568 low current.jpg]"

Peter,

Attachments are not allowed within our posts. However, you can post
your
picture(s) in the "PHOTOS" section. Make a File and share the
filename in a post. Then anyone can see the photos. Please edit and
reduce the size of the files to save our limited storage space on the forum.

Michael Lynch
Dardanelle, AR




--
Dennis Tillman W7PF
TekScopes Moderator