Date   

Re: New file uploaded to TekScopes@groups.io

Brian
 

Hi , I've just checked , latest winzip will open .rar archives also

Brian


From: n4buq <n4buq@...>
To: TekScopes@groups.io
Sent: Thursday, 1 February 2018, 17:15
Subject: Re: [TekScopes] New file uploaded to TekScopes@groups.io

7zip is free and will open either type.

Thanks,
Barry - N4BUQ


Hi , I dont have winzip any more , Winrar is out on the net for free download
. I'll try and do it in the next couple of days .
Brian


      From: esmondpitt <esmond.pitt@...>
  To: TekScopes@groups.io
  Sent: Thursday, 1 February 2018, 17:00
  Subject: Re: [TekScopes] New file uploaded to TekScopes@groups.io
   
Not wishing to be curmudgeonly but I haven't had or used a RAR archive
program for twenty years. Would it be possible to upload as ZIP? Or discrete
files?

Thanks in advance

EJP




   




Re: New file uploaded to TekScopes@groups.io

n4buq
 

7zip is free and will open either type.

Thanks,
Barry - N4BUQ

Hi , I dont have winzip any more , Winrar is out on the net for free download
. I'll try and do it in the next couple of days .
Brian


From: esmondpitt <esmond.pitt@...>
To: TekScopes@groups.io
Sent: Thursday, 1 February 2018, 17:00
Subject: Re: [TekScopes] New file uploaded to TekScopes@groups.io

Not wishing to be curmudgeonly but I haven't had or used a RAR archive
program for twenty years. Would it be possible to upload as ZIP? Or discrete
files?

Thanks in advance

EJP









Re: New file uploaded to TekScopes@groups.io

Brian
 

Hi , I dont have winzip any more , Winrar is out on the net for free download . I'll try and do it in the next couple of days .
Brian


From: esmondpitt <esmond.pitt@...>
To: TekScopes@groups.io
Sent: Thursday, 1 February 2018, 17:00
Subject: Re: [TekScopes] New file uploaded to TekScopes@groups.io

Not wishing to be curmudgeonly but I haven't had or used a RAR archive program for twenty years. Would it be possible to upload as ZIP? Or discrete files?

Thanks in advance

EJP


Re: TDS540B Power On Self Test Pass, but changing results from SPC

satbeginner
 

Hi Siggy,

thanks for your help, sadly enough I just put everything back together again, do you still have the type of the relays written down somewhere?
I think I read about somebody writing a small tool to exercise all the relays in a long loop overnight to clean the contacts of these relays, but I agree, if they are available replacing does make sense.

I worked on my machine today again, and there is some progress I'd like to report back:

I played with the attenuators a bit, and also found a way to "revive" the contacts of them.
I removed the attenuator-assembly from the acquisition board.
Remove the front bezel, and remove the plastic partial front around the 4x BNC connector.
Now remove the 5 screws along the BNC connectors,
After that I had -to remove the Acquisition board as a whole- 6-7 screws and 3 connectors on the side and 4 little coax connectors at the back.

Turn the board over and unplug the little bandcable for the buttons by unsecuring the cable clamp first.
Now remove the 10 screws holding the attenuator assembly, and carefully lift the board from from the assembly.

At that point, one can see the 2x black plastic frames holding a lot of little golden springs.
Carefully remove the 2 plastic frames and put these on a clean piece of paper kitchen towel and soak the springs in alcohol. (in my case the springs stayed in the plastic frames)
Be careful not to loose any springs!! (I did loose 2, and had to borrow 2 from the center ground bar. There are several there and I used one from each frame.)

I used a Q-tip soaked in alcohol to clean the contact surfaces of the 4x ceramic attenuator boards.
To "revive" the springs I used a very small pair of tweezers to stretch each spring a tiny bit. (again: be careful, here's where I lost mine!)

After assembly I still had errors, but now only related to the second channel, but both DAC errors AND level related errors.

To see if things were related to the attenuator only, I dismantled everything again and swapped Ch2 attenuator with the Ch4 attenuator.
To do that I had to loosen the one center solder tab on the front of the ceramic coming from the BNC, it could be done quite easily, although they seem quite fragile.

After assembly I tested again, but now I had two channels with errors: Ch2 AND Ch4... :-)
Ch2 with DAC errors (DDataL stuck High) and Ch4 with level related errors.
So, I swapped the two attenuators back to their original places, and decided I now had a TDS530B :-)
with only Ch1, Ch3 and Ch4 working and a dead/non reliable Ch2.

For now I will start using the scope to better learn how to use it and keep an eye out for both a DAC and an attenuator or -for starters- just the relays, maybe (probably?) they solve the level related errors.
I think it must have been hurt by some overvoltage, but after all, not a bad score for two days of hobby.

Here are the additional pictures: https://groups.io/g/TekScopes/album?id=21745

Un saludo,

Leo


Re: TDS540B Power On Self Test Pass, but changing results from SPC

Siggi
 

On Wed, 31 Jan 2018 at 17:33 satbeginner <@satbeginner> wrote:

I read something about the attenuators being/getting iffy, or at least the
contact sheets in between the ceramic attenuators and the PCB.
I downloaded every piece of documentation I could find from Häkan's site
and everywhere else, but I did not yet find info about how to clean the
attenuator contact sheets.
Hey Leo,

a common problem with these scopes is that the relays on the attenuator
hybrids become high resistance or even open contact. You can see what the
attenuators look like here <
https://www.eevblog.com/forum/testgear/tektronix-tds520b-attenuator-swap/>,
and it's the cluster of four yellow relays that often fail. On my TDS784D
this caused SPC failures, but by measuring the relay contact resistance, I
was able to identify the culprits. After replacing them, my scope's worked
like clockwork ever since. The relays a readily available, I bought mine
from DigiKey, though I couldn't find the part number readily.
Be careful when you handle and reinstall the hybrids, it's easy to
mis-position them and to crack and destroy them on reinstallation.

Siggi


New file uploaded to TekScopes@groups.io

TekScopes@groups.io Notification <TekScopes+notification@...>
 

Hello,

This email message is a notification to let you know that a file has been uploaded to the Files area of the TekScopes@groups.io group.

File: 040-0065-00.rar

Uploaded By: Brian

Description:
Tektronix 500 series blank plug-in data sheets

You can access this file at the URL:
https://groups.io/g/TekScopes/files/040-0065-00.rar

Cheers,
The Groups.io Team


Re: Thank you for Advice on ELECTRONIC LOADS

NigelP
 

Not really OFF-TOPIC when you consider the need to test all those Tek PSU modules properly! The great thing is that if you have a PSU with an over-current trip going off lower than it should you can quickly determine that.

It used mine for precisely that purpose last year; I had an electronic PSU for a camping fridge (CampingGaz) to check out that kept tripping. I found that while the PSU apparently could deliver its rated output current (5A), it ONLY JUST ABOUT made it and in the real world of the fridge load (probably non-linear at power-on due to motor start conditions) it mostly just crapped out, so appeared to be continually failing. I didn't find a schematic so couldn't be bothered to work out which component was causing the problem.... it wasn't mine and the owner just bought another one!

Nigel


Looking for 067-1331-00 Sampling Head Simulator. WTB.

Egge Siert
 

Hi to All,

Looking for this Service Fixture. Some years ago USA Only Seller CHIPXS sold tenths of them for little money. But that was before I got addicted to the 11K Series. Anybody who wants to seperate from such a device?

Greetings,

Egge Siert


SD-14 Mod BA

Egge Siert
 

Hi to all,

We all know the difference between between a Standard SD-14 and an Option 01 SD-14. Recently I saw several SD-14 Mod BA's for sale on eBay. These are all fitted with the SMB to Probe Tip Adapter which is also part of the Option 01 Package. Anybody who knows the in and outs?

See link below for documentation on Option 01:

https://www.artisantg.com/info/PDF__54656B74726F6E69785F534431345F557365725F4D616E75616C.pdf

Greetings,

Egge Siert


Re: 040-0065-00 blank plug-in for 500-series scopes

 

Hi Brian,

This is my address @yurighisio.

Many Thanks,
Juri


Re: TDS540B Power On Self Test Pass, but changing results from SPC

satbeginner
 

I created an album where I will put relevant pictures, it can be found here: https://groups.io/g/TekScopes/album?id=21745

Leo


TDS540B Power On Self Test Pass, but changing results from SPC

satbeginner
 

Hello all,

today I received an eBay (sold as is) TDS540B.
It would not power on, but that turned out to be a dirty Standby switch, also the front bezel was slightly dislocated towards the front, so the rubber of the switch could not touch the flexible circuit behind it.

The good news, after cleaning and repositioning the front it does power on and passes the Power On Selftest!
More good news: I seem to have newer boards in this machine, because there are hardly any SMD caps to be found, only a few, and these are all spotless clean, there is no sign of leakage whatsoever.

The bad news, although all 4 channels do respond to (calibration) input signals, some of them give intermittent wrong V/div readings, and these change when changing the input attenuator setting.
Sometimes at 50mV/div a channel would show a 1 div calibration signal, but when changing to 20mV/div it shows 3 div. (should be 2 1/2 div)

And sometimes when set at 5mV/div it will show the same as when set on 10mV/div, both 5 div, as if the attenuator does not change?
At the moment I am not sure, but Ch4 seems to work better then Ch1 and Ch2 and Ch3.
I can trigger the scope on all 4 channels.

When I run the SPC it does give errors like this:

Internal adjustment range ex (2@ 7012) 1.4650 ==> Balance DAC #3 (ID #146)
Internal adjustment range ex (1@ 7111) 1.1386 ==> Balance DAC #2 (ID #145)
Error: insufficient differential response (3@ 7493) 0.000 divs differential
Error: insufficient differential response (0@ 7493) 0.000 divs differential
Error: Characterized values out of b Ch3 trigger gain
Error: Characterized values out of b Ch3 trigger gain
Error:2260 Calibration Failed triggers

But: running the SPC again, or after a reboot, it might throw errors like:
Error: diagnostic test failure DDataL stuck Hi, Demux is 198
and some more.

But at power On the selftest is always Pass.

I read something about the attenuators being/getting iffy, or at least the contact sheets in between the ceramic attenuators and the PCB.
I downloaded every piece of documentation I could find from Häkan's site and everywhere else, but I did not yet find info about how to clean the attenuator contact sheets.

Any tips about how to clean these?
Any tips in general?

May thanks, un saludo,

Leo


Re: Help restoring a 547 scope

Albert Otten
 

Hi Felix,
Today and maybe also tomorrow I can't check my 547. I think such a check would be wise because it's easy to make mistakes in following the circuit description only.
The hold-off circuit around V145 appears to be nicely in the resting state. The cathode of V145A is at +1.5 V, slightly below 2 V in the manual. Hence from there slightly less bias current is added to D85 in your case. But since there is no way to adjust the D85 bias current I think this is not critical; the switching D45 will provide a high enough current pulse to D85 to force switching of D85. It could be that D85 is dead (shortcut I think).
From your present remarks I conclude that the B sweep does nothing when you select AUTO mode. You should test this without input signal and then measure the voltage (or waveform) at the collector of Q75. That voltage should increase to about +20 V and then the zener D76 should start to conduct and supply extra bias current to D85. That can be as much as 3 mA and should definitively be enough to switch D85 to its high state. That situation can only be reset after the end-of-sweep when the hold-off time starts. I think this measurement would be "of diagnostic value".


Re: Thank you for Advice on ELECTRONIC LOADS

 

Hi Ed,

Thanks for pointing that out. It will be a quick way to increase the voltage to the range I need. 400V makes me nervous ever since I got a nasty shock from a 400V transformer when I was in college 50 years ago. Ever since that incident I become extremely cautious around circuits where there is that much voltage and I take plenty of precautions. The irony is that at about the same age I was given a 15KV Neon Sign transformer which I played with extensively without ever getting a shock. To this day I have more fear of 400V than I do of 15KV.

Dennis Tillman W7PF

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Ed Breya via Groups.Io
Sent: Tuesday, January 30, 2018 10:02 PM
Subject: Re: [TekScopes] Thank you for Advice on ELECTRONIC LOADS

If you need to use an electronic load at higher voltage than it's made for, you can easily rig up a a high power Zener diode equivalent circuit in series to drop the voltage, and dissipate the excess power. For example, for a B+ supply in the 300-400V range, you can make an N-channel power MOSFET act as a shunt regulator in conjunction with say, 200-300V-worth of Zener diodes drop from D-G, allowing a 200V-rated load to handle it. A clamp circuit would be needed to make sure the electronic load's voltage can't get too high when its current is set very low. It will have some limitations, and need some figuring out of the external conditions and range requirements. The external shunt regulator will have to dissipate the extra power involved, of course.

Another, slightly more complicated option is to form a cascode stage with an external MOSFET, with gate biased (and G-S clamped and current-limited) to a fixed voltage somewhat less than the electronic load's rating. Virtually all of the current would then flow through the electronic load, for any test voltage above the gate bias, up to the MOSFET's Vds rating, while limiting the load's voltage to the gate bias level.

In any scenario, the load's output should be OVP'd, in case things go wrong. It's also good to add fuse protection at just over the maximum expected current, if it's not already provided. Reverse-polarity protection is intrinsic with most MOSFETs, as long as there's a fuse to clear/limit the fault current.

Ed



--
Dennis Tillman W7PF
TekScopes Moderator


Re: Help restoring a 547 scope

felix_cantor@...
 

I just realized that those sweeps are supposed to be taken with the triggering set at "auto" and "int". With those setting I get nuthin` at the test scope... just a boring straight line...

Thanks.


Re: Help restoring a 547 scope

felix_cantor@...
 
Edited

Hey there,

I uploaded an updated schematic to the link below with annotations in blue. Those readings that are "unstable" is because the DC voltage varies quite quickly up and down. Also the sweep that is indicated to be "unstable" wanders and moves around because of the unstable 5vDC component. I tried to use the hold-off adjustment in the test scope but couldnt bring it to a normal display. The sweep reading that is marked with an X is nonexistent, the test scope`s sweep remain at rest.


https://groups.io/g/TekScopes/photo/16016/2?p=Name,,,20,1,0,0

Let me know your thoughts please.

Thank you!


Re: 7603 working .... then blank

tinkera123
 

Hi,

Update on my 7603 scope ......

Removed Plug-ins and turned on Scope ...... Scope still dead.

Checked voltages at Pin P1171 .....
-15vdc and -50vdc ..... okay.
+5vdc, +15vdc, +50vdc and +130vdc ... all way out of spec.

Voltages at Pin P890 (unregulated V) show that all supplies are larger than expected .... probably due to being unloaded .....

Except the +130vdc supply .... which is +97vdc and -7.8vdc (instead of +130vdc and +40vdc).

I note that the Regulation circuits rely on other supplies to power the transistors. I am assuming for the moment (away from Home) that the +50v powering the +130v Regulation section (Q850, Q852 etc) is unregulated rather than regulated +50v .... ?? And just maybe, there might be no other faults .... 🤩

Next step is to check this Supply.

Cheers,
Ian


Re: Thank you for Advice on ELECTRONIC LOADS

Ed Breya
 

Oops - forgot to mention - since the this application is toward higher voltages, you can add reverse-protection withe a series diode, rather than having to clear a fuse via the body diode in the event that it's hooked up backwards. If it has to run at very low voltage (say 3.3V), a series diode may have too much drop, depending on the design. Ed


Re: Thank you for Advice on ELECTRONIC LOADS

Ed Breya
 

If you need to use an electronic load at higher voltage than it's made for, you can easily rig up a a high power Zener diode equivalent circuit in series to drop the voltage, and dissipate the excess power. For example, for a B+ supply in the 300-400V range, you can make an N-channel power MOSFET act as a shunt regulator in conjunction with say, 200-300V-worth of Zener diodes drop from D-G, allowing a 200V-rated load to handle it. A clamp circuit would be needed to make sure the electronic load's voltage can't get too high when its current is set very low. It will have some limitations, and need some figuring out of the external conditions and range requirements. The external shunt regulator will have to dissipate the extra power involved, of course.

Another, slightly more complicated option is to form a cascode stage with an external MOSFET, with gate biased (and G-S clamped and current-limited) to a fixed voltage somewhat less than the electronic load's rating. Virtually all of the current would then flow through the electronic load, for any test voltage above the gate bias, up to the MOSFET's Vds rating, while limiting the load's voltage to the gate bias level.

In any scenario, the load's output should be OVP'd, in case things go wrong. It's also good to add fuse protection at just over the maximum expected current, if it's not already provided. Reverse-polarity protection is intrinsic with most MOSFETs, as long as there's a fuse to clear/limit the fault current.

Ed


Thank you for Advice on ELECTRONIC LOADS

 

I had no idea I would get so many responses to my question about Electronic
Loads. I also did not have a clue how useful people have found them to be.
Until now I never had a use for one which, in retrospect, seems odd to me
after learning how indispensable people find them.



Whichever one I finally purchase it will probably be an "open frame"
inexpensive one I can modify without too much risk if I damage it. I did see
one that went up to 200V which is getting close to voltage range I need.
400V would be even better to test my next Vacuum Tube Curve Tracer design
which will be higher power and higher voltage than the first one.



Also, I didn't think of it at the time but I should have noted in the
subject line that my question was OFF TOPIC when I posted it.



Dennis Tillman W7PF