Date   

Re: My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

Albert Otten
 

On Mon, Apr 29, 2019 at 10:50 AM, Richard Knoppow wrote:


Where does it show the speed of light in a vacuum? The TDR
should be calibrated to the speed of light (electricity) in the
cable. For 50 Ohm cable its about 66% of c. Varies with the
impedance of the cable. If you know the physical length of the
cable you can determine both its impedance and the velocity from it.

On 4/29/2019 1:26 AM, Albert Otten wrote:
Interesting stuff Dennis! I have to look at it in more detail. I consider
repeating these tests since I have both Tek cables, though I don't have
quality SMA-BNC adapters.
Most remarkable is the slow speed of light in vacuum in the USA ;-)
Albert
--
Richard Knoppow
dickburk@ix.netcom.com
WB6KBL
The document says: "The speed of light in a vacuum is 224844343.5 m/Sec= 0.2248m/nSec. "
I guess Dennis already used some kind of velocity factor here. But this makes his following derivation invalid:
"The Velocity Factor (the speed the signal travels in the dielectric of this cable) is VF = 2* 36.0in * 0.0254m/in * 4.4475nSec/m/9.0nSec ~ 0.90. "

Albert


Re: 2465B Parametric Freq Measurement Error

Chuck Harris
 

All members of the 2465 family use interchangeable trigger hybrids.
To remove them, remove the four nuts at the corners of the module.

Tektronix considered them all to be "selected"... which I think meant
they tried them to see if they would work. the "-0X" suffix meant
changes in production usually... stuff like Tek vs Maxtek, or this
or that revision on their fabrication line...

I would suggest that your first attempted fix be to remove the module,
and clean the gold contacts with a Q-tip and IPA.

When you put the module back, seat it with finger pressure, and hold
it there as you finger tighten a pair of nuts on diagonal corners.
Then install the other pair of nuts. Tighten the nuts 1/4 turn past
where they just make contact. The tightness doesn't make or improve
electrical contact, so just 1/4 turn past the nut touching the hybrid
when it is touching the PCB.

I use one of the red plastic nutstarters that would be familiar to old
guys that built Heathkits. I wish I could find them new somewhere, but
I have enough to last my lifetime of used.

If cleaning the existing hybrid's contacts makes no improvement, then
swap in a hybrid from a working scope, and that should fix the problem.

-Chuck Harris

Tony Fleming wrote:

Is my Tektronix 2465 DMS using the same part number or do I need a
different one?
Where would I find more information how to perform the replacement?
Thanks.
Tony

On Sun, Apr 28, 2019 at 8:43 PM Chuck Harris <cfharris@erols.com> wrote:

The parametric measurements use the trigger hybrid extensively,
and their performance is directly related to how well that hybrid
performs. Some are better than others.

-Chuck Harris

joe@reforyou.net wrote:
After successfully calibrating my 2465B, it reports "All tests passed"
on start up. The question marks are all gone! My issue is with the
parametric measurement of frequency. When I attempt to measure the
frequency of a sine wave at frequencies higher than 10 MHz, the scope
reports the frequency as 35.62 kHz. Any test frequency above 10 MHz gets
the exact same report, 35.62 kHz. Below 10 MHz, it reports various
incorrect values (i.e. a 4.89 MHz signal is reported as 6.35 MHz). At
about 500 kHz and lower frequencies, the scope reports the correct
frequency. I have replaced the PAL at U975 - no change. Any suggestions?








Re: 2465B Parametric Freq Measurement Error

Chuck Harris
 

of course, but only cal03.

-Chuck Harris

joe@reforyou.net wrote:

If I replace the trigger hybrid, do I have to do the whole calibration again? Joseph Suste




Re: My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

Richard Knoppow
 

Where does it show the speed of light in a vacuum? The TDR should be calibrated to the speed of light (electricity) in the cable. For 50 Ohm cable its about 66% of c. Varies with the impedance of the cable. If you know the physical length of the cable you can determine both its impedance and the velocity from it.

On 4/29/2019 1:26 AM, Albert Otten wrote:
Interesting stuff Dennis! I have to look at it in more detail. I consider repeating these tests since I have both Tek cables, though I don't have quality SMA-BNC adapters.
Most remarkable is the slow speed of light in vacuum in the USA ;-)
Albert
--
Richard Knoppow
dickburk@ix.netcom.com
WB6KBL


Re: My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

Albert Otten
 

Interesting stuff Dennis! I have to look at it in more detail. I consider repeating these tests since I have both Tek cables, though I don't have quality SMA-BNC adapters.
Most remarkable is the slow speed of light in vacuum in the USA ;-)
Albert


Re: My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

Tom Gardner
 

Very timely: this weekend I picked up a Tek 1502B, and it came with a 012-0482-00 cable and a 011-0123-00 BNC 50ohm terminator. Apart from that I only have "generic" connectors and terminators, of variable quality.

Caveat: I don't understand the expected performance of the 1502B, and haven't calibrated it at all.

Having said that, the only significant difference from your report is the velocity factor. In order for the 1502B to show the cable's length as 3ft, I have to set the velocity factor to 0.67.

On 29/04/19 01:19, Dennis Tillman W7PF wrote:
I uploaded the results of my testing the SG503 012-0482-00 cable. In
addition I compared it to two other similar cables: a Tektronix 012-0057-00
50Ω cable, and a Pomona Electronics 50Ω cable.


It is located at:

https://groups.io/g/TekScopes/files/Evaluation%20of%20the%20Tektronix%20012-
0482-00%20cable%20for%20the%20SG503.pdf


Dennis Tillman W7PF


Re: My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

tek_547
 

I´m going to solder a 1m RG223 cable for my SG503 so this is interesting stuff for me.
Nice detailed piece of work Dennis, thanx!!


Re: 475A with High +110 rail

Renée
 

Michael-
I also would check the eb voltages  of Q1496 and Q1497 make sure nothing strange and xstrs are operating in their proper regions.
I would then take a hard look at CR1489 ( protection ec junction for pass xstr), almost seems like it might be leaking badly or possibly shorted bypassing the regulation. ( I had one go bad in a different supply....took a 5kv hit). It appears you have eliminated most everything else.
those are my guesses with the info provided. Someone else may have more insight.
Renée

On 2019-04-28 10:00 p.m., Mlynch001 wrote:
I have searched for a previous thread that was referred to in a post about a "high" 110 voltage rail on a 475 from back in 2012. I failed to find that post or any other applicable answer, perhaps I am not searching for the correct words? So I will ask for some help. I have a 475A with DM44 s/n B012228. After a thorough cleaning, I turned it on and find that for the most part it works great, no triggering issues, bright trace, all controls respond as expected, just dirty pots and switches. I supply various signals to the A and B channels and the scope displays a good trace with with amplitude matching the output of my signal generator, so calibration seems to be close enough for hobby work. The scope simply does not act as if there is anything wrong. For safety sake, I pulled the case and tested the various system voltages on the A9 interface voltage test points. I found everything to be spot on, except the +110 volt rail, Voltages as follows:
-15V = -14.998
-8V = -8.005
5V = 5.005
15V = 15.002
50V = 50.035
Unregulated 50V = 63.35
110V = 134.66

Line Voltage is 120V and the voltage calibrator on the transformer is set to the proper voltage. I pulled and tested Q1490, Q1494, Q1496 and Q1497. These all tested "good" with a transistor tester. I also replaced Q1490 and Q1494 with "Known Good" components, with no change noted in the +110V rail. I did not have exact replacements for Q1497 or Q1496, but they did both test good. I did go through to check and seat all the transistors that I could reach on all the boards. I checked the various resistors in LV +110 Supply regulator circuit (the ones I could reach) and found then to be very close to correct. I do not want to start un-soldering components without some idea of what to check next. I do not know if CR1489 has anything to do with the voltage regulation or not, but that component appears to be part of the +110 regulation system. Other than the "too high" +110 rail, the scope demonstrates no other issues, nothing smells "Hot" and no "magic smoke", The boards inside the scope are perfect, no signs of repairs, heat or damage. I just want to sort this out before I use the scope very much. Collector voltage on Q1497 is 134.5 and Q1496 at about 133.8. Almost everything agrees with the schematic EXCEPT that pesky +110V rail. Any ideas where to check next?


Re: My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

Craig Sawyers <c.sawyers@...>
 

Those are interesting measurements Dennis. And particularly interesting that although the
Pomona/Belden the impedance is not 50 ohms, although the variation seems to be very low. And it will
be more than an order of magnitude cheaper than the double shield Tek cable

Craig

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dennis Tillman W7PF
Sent: 29 April 2019 01:19
To: TekScopes@groups.io
Subject: [TekScopes] My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

I uploaded the results of my testing the SG503 012-0482-00 cable. In addition I compared it to two
other similar cables: a Tektronix 012-0057-00 50 cable, and a Pomona Electronics 50 cable.



It is located at:

https://groups.io/g/TekScopes/files/Evaluation%20of%20the%20Tektronix%20012-
0482-00%20cable%20for%20the%20SG503.pdf



Dennis Tillman W7PF



475A with High +110 rail

Mlynch001
 

I have searched for a previous thread that was referred to in a post about a "high" 110 voltage rail on a 475 from back in 2012. I failed to find that post or any other applicable answer, perhaps I am not searching for the correct words? So I will ask for some help. I have a 475A with DM44 s/n B012228. After a thorough cleaning, I turned it on and find that for the most part it works great, no triggering issues, bright trace, all controls respond as expected, just dirty pots and switches. I supply various signals to the A and B channels and the scope displays a good trace with with amplitude matching the output of my signal generator, so calibration seems to be close enough for hobby work. The scope simply does not act as if there is anything wrong. For safety sake, I pulled the case and tested the various system voltages on the A9 interface voltage test points. I found everything to be spot on, except the +110 volt rail, Voltages as follows:
-15V = -14.998
-8V = -8.005
5V = 5.005
15V = 15.002
50V = 50.035
Unregulated 50V = 63.35
110V = 134.66

Line Voltage is 120V and the voltage calibrator on the transformer is set to the proper voltage. I pulled and tested Q1490, Q1494, Q1496 and Q1497. These all tested "good" with a transistor tester. I also replaced Q1490 and Q1494 with "Known Good" components, with no change noted in the +110V rail. I did not have exact replacements for Q1497 or Q1496, but they did both test good. I did go through to check and seat all the transistors that I could reach on all the boards. I checked the various resistors in LV +110 Supply regulator circuit (the ones I could reach) and found then to be very close to correct. I do not want to start un-soldering components without some idea of what to check next. I do not know if CR1489 has anything to do with the voltage regulation or not, but that component appears to be part of the +110 regulation system. Other than the "too high" +110 rail, the scope demonstrates no other issues, nothing smells "Hot" and no "magic smoke", The boards inside the scope are perfect, no signs of repairs, heat or damage. I just want to sort this out before I use the scope very much. Collector voltage on Q1497 is 134.5 and Q1496 at about 133.8. Almost everything agrees with the schematic EXCEPT that pesky +110V rail. Any ideas where to check next?


--
Michael Lynch
Dardanelle, AR


Re: 2465B Parametric Freq Measurement Error

Tony Fleming
 

Is my Tektronix 2465 DMS using the same part number or do I need a
different one?
Where would I find more information how to perform the replacement?
Thanks.
Tony

On Sun, Apr 28, 2019 at 8:43 PM Chuck Harris <cfharris@erols.com> wrote:

The parametric measurements use the trigger hybrid extensively,
and their performance is directly related to how well that hybrid
performs. Some are better than others.

-Chuck Harris

joe@reforyou.net wrote:
After successfully calibrating my 2465B, it reports "All tests passed"
on start up. The question marks are all gone! My issue is with the
parametric measurement of frequency. When I attempt to measure the
frequency of a sine wave at frequencies higher than 10 MHz, the scope
reports the frequency as 35.62 kHz. Any test frequency above 10 MHz gets
the exact same report, 35.62 kHz. Below 10 MHz, it reports various
incorrect values (i.e. a 4.89 MHz signal is reported as 6.35 MHz). At
about 500 kHz and lower frequencies, the scope reports the correct
frequency. I have replaced the PAL at U975 - no change. Any suggestions?






Re: 2465B Parametric Freq Measurement Error

joe@...
 

If I replace the trigger hybrid, do I have to do the whole calibration again? Joseph Suste


Re: 2465B Parametric Freq Measurement Error

Chuck Harris
 

The parametric measurements use the trigger hybrid extensively,
and their performance is directly related to how well that hybrid
performs. Some are better than others.

-Chuck Harris

joe@reforyou.net wrote:

After successfully calibrating my 2465B, it reports "All tests passed" on start up. The question marks are all gone! My issue is with the parametric measurement of frequency. When I attempt to measure the frequency of a sine wave at frequencies higher than 10 MHz, the scope reports the frequency as 35.62 kHz. Any test frequency above 10 MHz gets the exact same report, 35.62 kHz. Below 10 MHz, it reports various incorrect values (i.e. a 4.89 MHz signal is reported as 6.35 MHz). At about 500 kHz and lower frequencies, the scope reports the correct frequency. I have replaced the PAL at U975 - no change. Any suggestions?




Re: 2246 no display/odd behavior

 

Take note of where the grid bias R2719 is currently set by following the setup in the manual. You will do this in XY mode. See if you can get a dot displayed.

I agree that all the power supply rails look good.

The battery can be any 3.6 volt lithium cell with leads just for a test.

Good luck and regards


2465B Parametric Freq Measurement Error

joe@...
 

After successfully calibrating my 2465B, it reports "All tests passed" on start up. The question marks are all gone! My issue is with the parametric measurement of frequency. When I attempt to measure the frequency of a sine wave at frequencies higher than 10 MHz, the scope reports the frequency as 35.62 kHz. Any test frequency above 10 MHz gets the exact same report, 35.62 kHz. Below 10 MHz, it reports various incorrect values (i.e. a 4.89 MHz signal is reported as 6.35 MHz). At about 500 kHz and lower frequencies, the scope reports the correct frequency. I have replaced the PAL at U975 - no change. Any suggestions?


My TDR Evaluation of the SG503 012-0482-00 Cable has been uploaded

 

I uploaded the results of my testing the SG503 012-0482-00 cable. In
addition I compared it to two other similar cables: a Tektronix 012-0057-00
50Ω cable, and a Pomona Electronics 50Ω cable.



It is located at:

https://groups.io/g/TekScopes/files/Evaluation%20of%20the%20Tektronix%20012-
0482-00%20cable%20for%20the%20SG503.pdf



Dennis Tillman W7PF


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: Evaluation of the Tektronix 012-0482-00 cable for the SG503.pdf

Uploaded By: Dennis Tillman W7PF

Description:
Detailed TDR examination of the SG503 012-0482-00 cable with a comparison to three other similar cables.

You can access this file at the URL:
https://groups.io/g/TekScopes/files/Evaluation%20of%20the%20Tektronix%20012-0482-00%20cable%20for%20the%20SG503.pdf

Cheers,
The Groups.io Team


2246 no display/odd behavior

Matt
 

Ok. I've removed the battery - have a new one on order. When reassembling I found that J2208 was installed backwards initially. Corrected but no change in behavior. All further testing is done with the battery removed:

Exact voltages:
+131.34
+58.201
+15.052
+7.4913
+5.2186
-5.2245
-7.5541
-16.005

These all seem to be in spec.

I have a 6kV probe on order - should be here in a few days. I will probe the HV line at that point.

Beam finder does nothing. There is no display at all - no text, no beam. No change whether the front panel is powered up or not.


Re: SG504 or 503 cable

 

Ok, compared the RG-58 Tektronix cable to an RG-400 I built of similar length.
At 200Mhz and 4Vpp (x1 amplitude) we have ....

The OEM Tektronix cable clocked in at 0.20 dBm low.

DIY RG-400 cable was only 0.01 dBm low!!

Now B4 you guys roast me over the Boonton 4210 microwattmeter with the 4210-4B sensor....
I make no claims, infer from the results what you will (expect 1.5% accuracy from the Boonton).

But...I feel pleased that the SG 503 combined with a RG-400 cable and the Boonton show what could be a nearly perfect output.
I must mention that I recently serviced the SG 503 using liquid de-oxit on the rotary frequency selector contacts and polished the brass nut and seat contact point on the variable tuning capacitor.

~A


Re: 2246 no display/odd behavior

 

How can you edit a post on this system?
Anyway-
Have you replaced the battery yet? Should do that first and reboot the scope several times to get the ram initialized.

Pay attention to the adjustments section, especially the power supply and beam (grid bias) adjustments.

What are the _exact_ low voltage measurements?

The ripples shown on your pictures all look good.

Can you measure the -2.7 kV line safely? That can be accessed by looking at the cathode or filaments on the CRT.

Does the Beam finder button do anything?

Regards

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