Date   

Re: 2465B Parametric Freq Measurement Error

Chuck Harris
 

Hi John,

Best would be to swap the trigger hybrid from one of your
2465 family scopes that does work into the one that doesn't
work, as a test. (as long as you restore the original to the
calibrated scope, there will be no affect on calibration.)

The trigger hybrid is crucial to everything in the parametric
functions.

An additional place to look would be to follow the signal from the
DAC to the trigger hybrid threshold inputs (TLA, TLB). The 4051's
and the TL072's and their associated sample and hold gate parts go
bad sometimes (U2521, U2520, U2420, C2421, C2621).

One repair/calibration blurs into the next. If you think I didn't
repair something correctly, send it back, and I will fix it gratis.

I know I tested the parametric functions on the unit I calibrated.
It is a standard part of the tektronix calibration routines.

-Chuck Harris

John Ferguson via Groups.Io wrote:


Hi Chuck,

The parametric functions do not work on one of my 2445Bs, the one you didn't
calibrate.? It also doesn't sync on signal on start-up but does work well manually.?
I chased this around? on EVblog a few years back, but never arrived at what to look at.

Is it possible that cleaning up the contacts and gently re-seating a hybrid could
resolve this? Would it make sense to buy a replacement hybrid just in case the
clean-up doesn't produce the desired result?

best regards

john




Re: 475A with High +110 rail

Dave Hills
 

With 134v on Q1496 collector, you should see +61v at Q1490's base. This will completely shut down the regulator by reverse biasing Q1494 b-e. That said it only leaves R1483, Q1496, CR1498, and R1488 as likely suspects. R1483 would have to have drifted VERY low, (unlikely), or R1488 VERY high, (possible, but not likely to cause these symptoms), leaving a leaky or shorted Q1496 or CR1489. Note that an OPEN CR1489 would likely cause Q1496 to subsequently fail. Also, check that CR1489 has not been installed backward.

Please forgive the caps, not shouting, just no other way to highlight for emphasis.

Dave


Re: 2465B Parametric Freq Measurement Error

John Ferguson
 

Hi Chuck,

The parametric functions do not work on one of my 2445Bs, the one you didn't calibrate.? It also doesn't sync on signal on start-up but does work well manually.? I chased this around? on EVblog a few years back, but never arrived at what to look at.

Is it possible that cleaning up the contacts and gently re-seating a hybrid could resolve this? Would it make sense to buy a replacement hybrid just in case the clean-up doesn't produce the desired result?

best regards

john


2465 repair attempt with (horizontal?) issues, help needed

satbeginner
 

Hi all,

I got (yet another for my collection) 2465, it was stated it had problems before I got it, so no problem there.
What have I done so far:

Recapped the Power Supply, cleaned the Siemens fan and powered the scope up.
Power supply is OK, all voltages are well within range in terms of value and ripple, set the reference voltage for 10V.
Control DAC and reference are checked and set for a 2.5V range.

After Power-On I have a straight trace, not really focussed perfectly, but more interesting: I got no proper readout, I have two blurry lines at the top and bottom of the screen.
When I apply a calibration signal from the scope itself when on Auto Lvl the triggered light goes on, but the image looks like if it is not triggered, because I see just two horizontal lines.
They seem to be the high and low level of the calibration signal.

When I switch on the Voltages cursors they seem OK, a little vague, but the respond to the delta-settings knobs, but when I switch to the vertical (Time Cursors) I see some vague light in the tube as if the beam is hitting the sides?
The trace stays where it is.

Now the weird thing: as I am looking for causes, I tried the following:

When I put the scope on X-Y mode using Ch2 I get a line instead of a dot??
When I check the outputs of the U800 I have clean static DC voltages (cursors and readout switched off) approx. between 20 and 60V, depending on the Ch1 position, so that should be a dot, but it is a horizontal line......????
Vertical position of this line (that should be a dot) is nicely controlled by the Ch2 position.

When not in X-Y mode, the horizontal trace appears to be way to wide as well, so it looks like something other that the U800 is causing a horizontal deflection?

Any ideas where this line / horizontal deflection is coming from?
It's a line, so it should be some changing signal, but now I could use some tips and tricks.

Thank and un saludo,

Leo

I


Re: 2465B Parametric Freq Measurement Error

Tom B
 

Hi Chuck,

Exactly!
Have you tried their product?
Nope. I found others for sale, but these were cheaper.

Tom


-Chuck Harris

Tom B wrote:
Hi Chuck,

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.
Like this:


Re: 2465B Parametric Freq Measurement Error

Chuck Harris
 

Exactly!

Have you tried their product?

-Chuck Harris

Tom B wrote:

Hi Chuck,

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.
Like this: http://smallbear-electronics.mybigcommerce.com/nut-starter/

Tom





Re: 475A with High +110 rail

tom jobe <tomjobe@...>
 

On the 474A L.V. schematic it shows the expected voltage at the emitter of Q1496 as being 135.6 volts, which is quite close to your 134.66 reading at your +110 test point.
It shows the expected voltage at the +110 test point as being 111 volts with only R1488 and Q1496 directly between the +110 test point and the expected 135.6 volts at the emitter of Q1496.
Maybe you can find the problem by probing around right in that area?
tom jobe...

On 4/28/2019 10:00 PM, 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: 2465B Parametric Freq Measurement Error

Tom B
 

Hi Chuck,

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.
Like this: http://smallbear-electronics.mybigcommerce.com/nut-starter/

Tom


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

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