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Re: Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

n49ex
 

No sense hunting around all over. I would suggest go to the 7B92's connector in the back and directly check the power pins to ground. They are on the A connector side: +50 net pin 19, +15 net pin 18 (and it's most likely short C972), +5 lights pin 9, +5 pin 8; on the B side pin 18 is -15 (with it's most likely C976). Once you identify the shorted supply there (something in the few ohms or less region), THEN start chasing it down on that power net. Schematic and full maintenance manual is on TEkWiki  http://w140.com/smb/7b92a_sm.pdf

I've always thought the 7B92A was an absolute design masterpiece when you think about how much functionality they crammed into this space (for the time), and the astonishing analog triggering performance. One of my all time favorite Tek accomplishments, right up there with the (7904) distributed delay line CRT deflection system - and the roadrunner meep-meep cartoon on the first edition manual schematic of the vertical output!

Reinhard


Re: Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

Eric
 

If I remember correctly there is a separate small 5V rail especially for the lamps and lights. You have to add the connections for a 7603. As it does not have it. Most likely this is what is being dragged down. It wont effect the scope. I have bad news on the trigger light though If I remember correctly that is driven from a custom tech IC. I had one of those burned out in an A plugin it did share the IC with a 485 of which I had a parts unit for. If you are looking for shorts on the main 5V supply I do not think you will find them. At least for the lamps.

Eric

-----Original Message-----
From: TekScopes@groups.io <TekScopes@groups.io> On Behalf Of Dave Daniel
Sent: Sunday, February 7, 2021 1:43 PM
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

Ummm... I’m not sure hot-plugging a 7xxx plug-in is a good idea since they were not designed for that. The result will depend on the sequence of contact between the plug-in board fingers and the 7904 connector contacts when the plug-in is inserted (hint: they will not all make contact at the same time).

All hot-plug systems of which I am aware have different length pins/fingers which serve to control how the circuits on the hot-pluggable board are activated as well as active circuitry to protect things during power-up.

DaveD

On Feb 7, 2021, at 12:07, robeughaas@gmail.com wrote:

It's been a while since I've been inside a 7904, but I'm sure it has some accessible power-supply test points. With power off and the plug-in not installed, measure the resistance of each test point to ground. Then, with the power still off, insert the plug-in and measure the test points again. They may measure under 100 ohms, but should not be under 10 ohms. This should identify which supply the plug-in is shorting and suggest which caps on the plug-in to look for. Tantalums don't always show external distress when they short so dont rely on a visual check.

--
Bob Haas





Re: 549 transformer question

Joel B Walker
 

Just looking at various vintage Tektronix scope schematics, it seems to me that other "beeswax" type HV transformers could be adapted to work as in the example described in the previous post. The basic circuitry is nearly identical in many of them. Just wondering. I may try the 564 thing myself.


Re: sighting: Beaverton-built 5110 Mod 709V for Bently Nevada

 

On Sun, Feb 7, 2021 at 09:00 PM, Paul McClay wrote:

May I add that excerpt to TekWiki?
Off course

Do you have any digital copy of the manual? Or a part number for the manual?
No, only on micro fiche and I don't have a working M/F scanner.
These are not manuals but Manual Inserts which was supposed to be added to the original manual.
As such they did not have a 070- number. Some might have document number and on the scope
insert there was a handwritten number as 061-1473-00. Nothing on the plugins.

Does Mod 709V include the other colored binding posts on the plugins?
The mod info on the plugins:
//
5A19N MOD 709V
This manual insert describes the features of MOD 709V as installed in the 5A19N
Differential Amplifier. The Signal Input connector has been changed to a blue
binding post for the Minus Input. The Variable VOLTS/DIV control labeled CAL
has been removed. A +15 Volts offset, regardless of the VOLTS/DIV control
setting has been added

5B10N MOD 709V
This manual insert describes the features of MOD 709V as installed in the 5B10N
Time Base Amplifier. It removes the VAR control, changes the BNC EXT INPUT
connector to a green binding post and provides a switching mode for
Left Vertical vs Right Vertical, The last ccw position of the SECONDS/DIV or
VOLTS/DIV (EXT) switch is now labeled L vs H.
//

/Håkan


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Attilio
 

Hi Miguel,
OK, tomorrow I'll try, I act on R412.

Thank you.
--Cheers
Attilio


Re: Teitronix 492a : TUNING FAILURE - 1st LO

Miguel Work
 

I have found two defective DM74LS72 in other Tektronix equipment, in a 214 and 212 oscilloscopes with no clue why the chip failed

-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de ulf_r_k via groups.io
Enviado el: domingo, 7 de febrero de 2021 21:44
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] Teitronix 492a : TUNING FAILURE - 1st LO

Following a hint from KO4BB when experiencing occasional lock errors, in the Synthesizer unit A50 there are two IC's that I had to replace.
In the larger box, the middle circuit board has two IC's U2050 = 74LS10 and U1050 = 74LS74. I had to replace both of them.
Not sure about it, I used high quality sockets but that did not affect the function of the repaired unit/analyzer.

in order for the YIG LO to lock. Also replacing electrolytic capacitors is neccessary. Be careful arond the YIG though. Tek obvisously had a lot of problem to get the supply voltages clean, having to add several filtering components in the little harness connecting to the YIG LO.

Otherwise, the Service Note documentation on the home page of KE5FX is a good source of information.
I salvaged an old 494P that had been left in a damp shed for years. Enough to make the front panel corrode and insects having found new homes. Eventually, I was able to revive the analyzer.







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Re: 549 transformer question

Joel B Walker
 

Is that part number 120-0275-00 for the 564 HV transformer?


Re: Teitronix 492a : TUNING FAILURE - 1st LO

ulf_r_k
 

Following a hint from KO4BB when experiencing occasional lock errors, in the Synthesizer unit A50 there are two IC's that I had to replace.
In the larger box, the middle circuit board has two IC's U2050 = 74LS10 and U1050 = 74LS74. I had to replace both of them.
Not sure about it, I used high quality sockets but that did not affect the function of the repaired unit/analyzer.

in order for the YIG LO to lock. Also replacing electrolytic capacitors is neccessary. Be careful arond the YIG though. Tek obvisously
had a lot of problem to get the supply voltages clean, having to add several filtering components in the little harness connecting to the YIG LO.

Otherwise, the Service Note documentation on the home page of KE5FX is a good source of information.
I salvaged an old 494P that had been left in a damp shed for years. Enough to make the front panel corrode
and insects having found new homes. Eventually, I was able to revive the analyzer.


Re: Teitronix 492a : TUNING FAILURE - 1st LO

Miguel Work
 

http://www.ke5fx.com/49x_notes.pdf





-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Bent Andersen
Enviado el: sábado, 6 de febrero de 2021 17:32
Para: TekScopes@groups.io
Asunto: [TekScopes] Teitronix 492a : TUNING FAILURE - 1st LO

Hello all

I have now time to look at my old Tek492a there is showing up a error when it startup...pse look at the video link: https://photos.app.goo.gl/c3xCHVpAN6LVdvtq8 any idea where I start to look for broken parts ???

there is also another proble...is the key respons so slowly, from you hit the key and until the light is on 1-2sec ????

Best regards

Ben


Re: Teitronix 492a : TUNING FAILURE - 1st LO

Miguel Work
 

Hi,

Do you have a second SA to check the 1st output?

https://www.youtube.com/watch?v=G3A-4Jrtv3s

There´s is a document with 492P repair tips:

http://www.kolumbus.fi/oh5iy/HW/Tektronix.html

Regards!






-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de Bent Andersen
Enviado el: sábado, 6 de febrero de 2021 17:32
Para: TekScopes@groups.io
Asunto: [TekScopes] Teitronix 492a : TUNING FAILURE - 1st LO

Hello all

I have now time to look at my old Tek492a there is showing up a error when it startup...pse look at the video link: https://photos.app.goo.gl/c3xCHVpAN6LVdvtq8 any idea where I start to look for broken parts ???

there is also another proble...is the key respons so slowly, from you hit the key and until the light is on 1-2sec ????

Best regards

Ben


Re: sighting: Beaverton-built 5110 Mod 709V for Bently Nevada

Paul McClay
 

Thanks Håkan!

From a look at your panorama of Tek gear, and fische reader, I should not be surprised that you have the manual!

A few more questions:

May I add that excerpt to TekWiki?

Do you have any digital copy of the manual? Or a part number for the manual?

Does Mod 709V include the other colored binding posts on the plugins?

===

I wonder if the story of how this mod came to be and who bought it includes anyone other than Bently Nevada.


Re: Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

Ed Breya
 

For 7K plug-ins, you can do it on the bench, just the plug-in alone, opened up for access. Probe around with an ohmmeter and check across each Ta cap for short or very low R, and mark any that show this. Also check for signs of overheating of series Rs and Ls in the power supply buses. Don't worry about which supplies and caps are which, or that you can't necessarily see or access every Ta in there. Go for the easy stuff first. After you've marked any bad ones, lift one lead - un-solder or clip close to the board (leaving some lead to tack it back) - and check the part itself, and at the board pads. Often, more than one part spot will show bad because there may be several caps on the same bus, and any one bad will cause all of the spots to show the same. Then you just figure out which ones are actually shorted and remove. Don't replace any until the plug-in can fire up and operate without crashing the mainframe. If you can't find any easy ones to blame, you'll have to dig deeper and look for more. In my experience, shorted Ta caps in plug-ins are almost always on the +/- 15 V supplies - that's where they're used the most. Also, don't be surprised if another cap shorts after fixing. Sometimes they chain react, where eliminating the shorted one allows the supplies to return, and the next weakest one pops, and so on. I remember once in an EIP counter, I had about half a dozen or more Ta caps on the +5 V supply light up and burn, one after another - after clipping the burnt one, the next would go within a minute or so.

Ed


Re: Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

Dave Daniel
 

Yes, you are correct. I mis-read his email. My apologies.

DaveD

On Feb 7, 2021, at 13:54, Colin Herbert via groups.io <colingherbert=blueyonder.co.uk@groups.io> wrote:

It seems to me that Bob was quite clear that the power should be OFF. Maybe you just didn't read that bit thoroughly? There are often, if not always, notices on the mainframe to warn against installing or removing plug-ins while power is ON - It's a no-no.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Daniel
Sent: 07 February 2021 18:43
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

Ummm... I’m not sure hot-plugging a 7xxx plug-in is a good idea since they were not designed for that. The result will depend on the sequence of contact between the plug-in board fingers and the 7904 connector contacts when the plug-in is inserted (hint: they will not all make contact at the same time).

All hot-plug systems of which I am aware have different length pins/fingers which serve to control how the circuits on the hot-pluggable board are activated as well as active circuitry to protect things during power-up.

DaveD

On Feb 7, 2021, at 12:07, robeughaas@gmail.com wrote:

It's been a while since I've been inside a 7904, but I'm sure it has some accessible power-supply test points. With power off and the plug-in not installed, measure the resistance of each test point to ground. Then, with the power still off, insert the plug-in and measure the test points again. They may measure under 100 ohms, but should not be under 10 ohms. This should identify which supply the plug-in is shorting and suggest which caps on the plug-in to look for. Tantalums don't always show external distress when they short so dont rely on a visual check.

--
Bob Haas














Re: Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

Colin Herbert
 

It seems to me that Bob was quite clear that the power should be OFF. Maybe you just didn't read that bit thoroughly? There are often, if not always, notices on the mainframe to warn against installing or removing plug-ins while power is ON - It's a no-no.
Colin.

-----Original Message-----
From: TekScopes@groups.io [mailto:TekScopes@groups.io] On Behalf Of Dave Daniel
Sent: 07 February 2021 18:43
To: TekScopes@groups.io
Subject: Re: [TekScopes] Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

Ummm... I’m not sure hot-plugging a 7xxx plug-in is a good idea since they were not designed for that. The result will depend on the sequence of contact between the plug-in board fingers and the 7904 connector contacts when the plug-in is inserted (hint: they will not all make contact at the same time).

All hot-plug systems of which I am aware have different length pins/fingers which serve to control how the circuits on the hot-pluggable board are activated as well as active circuitry to protect things during power-up.

DaveD

On Feb 7, 2021, at 12:07, robeughaas@gmail.com wrote:

It's been a while since I've been inside a 7904, but I'm sure it has some accessible power-supply test points. With power off and the plug-in not installed, measure the resistance of each test point to ground. Then, with the power still off, insert the plug-in and measure the test points again. They may measure under 100 ohms, but should not be under 10 ohms. This should identify which supply the plug-in is shorting and suggest which caps on the plug-in to look for. Tantalums don't always show external distress when they short so dont rely on a visual check.

--
Bob Haas





Re: Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

Dave Daniel
 

Ummm... I’m not sure hot-plugging a 7xxx plug-in is a good idea since they were not designed for that. The result will depend on the sequence of contact between the plug-in board fingers and the 7904 connector contacts when the plug-in is inserted (hint: they will not all make contact at the same time).

All hot-plug systems of which I am aware have different length pins/fingers which serve to control how the circuits on the hot-pluggable board are activated as well as active circuitry to protect things during power-up.

DaveD

On Feb 7, 2021, at 12:07, robeughaas@gmail.com wrote:

It's been a while since I've been inside a 7904, but I'm sure it has some accessible power-supply test points. With power off and the plug-in not installed, measure the resistance of each test point to ground. Then, with the power still off, insert the plug-in and measure the test points again. They may measure under 100 ohms, but should not be under 10 ohms. This should identify which supply the plug-in is shorting and suggest which caps on the plug-in to look for. Tantalums don't always show external distress when they short so dont rely on a visual check.

--
Bob Haas





Re: Spectrum analyser

Miguel Work
 

Hi!

One of mines had a problem with the phase locked loop too. One of the vararactor diodes was shorted in the BAND C oscillator

Is the RF center frequency working?

When you push lock check and you moves the RF center frequency, you see DC level in screen?

I have two manuals, one is 109 Mb, the other one is the US Army that you have.

There are two versions of the BAND C oscillator, one with tube, and the other with transistor, solid state.

Manual:
http://w.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix/Tektronix_-_491_Spectrum_Analyzer

Band C varactor diode fix:

https://groups.io/g/TekScopes/album?p=Name,,,20,1,20,0&jump=1&id=86588






-----Mensaje original-----
De: TekScopes@groups.io [mailto:TekScopes@groups.io] En nombre de michel soldevila
Enviado el: domingo, 7 de febrero de 2021 18:23
Para: TekScopes@groups.io
Asunto: Re: [TekScopes] Spectrum analyser

Hi Miguel,
1. I would like to get the Tek user's manual ; the one I have was issued by the US army (TM 9-6625-2467-15).
2. I am unable to reproduce the phase locking tests described on page 2-7 of this manual. I wonder if it indicates a failure.
Regards







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Re: So while we are all here talking oscilloscopes

snapdiode
 

I've worked with Russians and really liked their pragmatic approach to things.


Re: So while we are all here talking oscilloscopes

ditter2
 

I have heard that YES, they did. I am not sure about directly viewed CRTs, but they did make scan converter tubes similar to the one Tek used in the 7912AD. I heard this second hand, from an engineer working for EG&G at the Nevada Test Site (US Atomic underground nuclear weapon test facility – for those outside of the USA). He heard it directly from one of his Russian counterparts.

I visited the NTS while conducting research for a proposed very high channel count, low frequency VXI based digitizer Tek was considering. The nuclear weapons reduction treaty in effect at the time was shutting down testing, and the NTS was preparing for their very last test. Per the treaty, Russian test engineers actually were invited to witness the previous test, and a reciprocal visit by the US engineers would occur at their next test.

Much of the technology was declassified and the EG&G were even bragging about the technology used for data capture. The transient digitizers were the latest Tek SCD5000 which had a whopping BW of 5 GHz. This was a big step up from the 3 GHz that was state of the art for nearly a decade before the SCD5000. The Russians were not impressed. They said (and was later verified) that their digitizers had 13 GHz BW. The EG&G engineers questioned, and were told that the Russian units use scan converter CRT technology, with TW deflection, similar to the design Tek used. The difference was the length. While the military specifications for the US digitizers required they fit inside a standard 19” rack with no more than 30” depth. The Russians did not restrict the depth, and used a scan converter that is over 3 m in length! The long distance between the deflection plates and target require very low deflection angle, facilitating higher BW.

The EG&G engineers went on the say what impressed the Russians the most was not the measurement technology, but rather than the NTS used tunnel boring machines which left smooth walls in the test hole. The Russians simply blasted their tunnels with dynamite.


Re: Spectrum analyser

michel soldevila
 

Hi Miguel,
1. I would like to get the Tek user's manual ; the one I have was issued by the US army (TM 9-6625-2467-15).
2. I am unable to reproduce the phase locking tests described on page 2-7 of this manual. I wonder if it indicates a failure.
Regards


Re: Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe

 

It's been a while since I've been inside a 7904, but I'm sure it has some accessible power-supply test points. With power off and the plug-in not installed, measure the resistance of each test point to ground. Then, with the power still off, insert the plug-in and measure the test points again. They may measure under 100 ohms, but should not be under 10 ohms. This should identify which supply the plug-in is shorting and suggest which caps on the plug-in to look for. Tantalums don't always show external distress when they short so dont rely on a visual check.

--
Bob Haas

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