Date   

Re: 576 serials

Michael W. Lynch
 

On Sun, Feb 7, 2021 at 10:26 AM, Glydeck wrote:


Is there any other meta data we should submit? HV transformer type, etc. A
simple list of SN#s doesn’t seem particularly useful.
Certainly a good suggestion. I am documenting whatever anyone shares at this point. Some are sending IC date codes, others are sending CRT information. I would certainly appreciate any other suggestions of data that folks would like to see gathered. If anyone wants to add or change information regarding their instrument, just reference your S/N and add the new data, I will sort it out.

Thanks!



--
Michael Lynch
Dardanelle, AR


Re: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Attilio
 

Many thanks Ed,
I have read everything you wrote to me, I only have a couple of questions: when I reconnect P446 and the PLL commands the oscillator at 2072 MHz, the frequency meter where I connect it, considering that if I have to make the PLL work the IF output connector will be connected to the 110 MHz amplifier input ?
I could connect the frequency meter to the 110 MHz amplifier input.
When I connect the 2nd LO of the 7L13 (SA) to the 2nd LO of the TR503, on the oscilloscope should I see a line positioned at about + 15 Vdc?
Now I have the 52.5 MHz crystal on the PLL reference oscillator, should I leave it or put the 55 MHz one back on? I think the 52.5 MHz one should be left.

Tomorrow I'll try to carry out all the tests, then I'll tell you.

Thanks again.
-- Cheers
Attilio


TEK 465 S/N>25000 Power Supply Issue

Craig Cramb
 

Got a 465 that was somewhat functional but no trace with blown F1419. Went thru Groupsio file library and replaced the C1419 and that got the signal trace. Reviewed the Power supply and here are the original results.
-8 =7.79vdc, 265mvAC
+15 =13.13vdc, 2.26 mvAC
+55 = 53.7vdc, 1.8 VAC
+5 =4.88vdc, 156 mvAC
+110= 110.9 vdc 1.8 VAC

Decided to recap the unit with all input PS filter caps. Got this completed and then I had this result.
-8= .585vdc .4mvAC
+15=1.6vdc .3mvAC
+55=46vdc .7mvAC
+5= .788vdc .3mvAC
+110= 107.3 vdc , 6.2mvAC
Replaced the CR1541

Started trying to determine the possible issue and determined that I had no +22vdc at U1524A&B input. So continued on going thru the +55 regulator and determined that if I left pin 1 out of the U1524 base socket the +22 vdc would show up. So then re-socketed the pin 1 along with all others and it would drop +22 again to 2.26Vdc. So I moved to the B section of chip U1524 and removed pin 7 with all the others in the socket the +55 V would go to 54.9vdc. At this point decided to move onto the +15 section of the regulated supply. Went thru and disconnected jumpers, and plug connectors checked components as per the troubleshooting of the +15,+5,-8 in the manual. Rechecked with power applied and the voltages all went back to the low value readings. Traced it down to the Q1544 transistor when it was removed the U1524 amplifier voltages would come up to as the markings in the manual for voltages except for the lead 6 of the U1524B. Swapped it out the Q1544 with no change. So now if I just disconnect the base of transistor Q1544 +55 and voltage readings around the U1524 a&b are as needed along with the +55. Thinking that the Q1546 is causing the issue. As I have basically gone thru and checked all the resistors, capacitors and diodes involved in the circuit down to the TP1548 +15VDC. Including the Q1546 and don't see any issue.

Any thought are welcomed on this issue.
Craig


Re: 7L13 parts needed

Joel B Walker
 

I guess these are rarer than I thought. Surely there are some somewhere.............................


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

Ed Breya
 

Reinhard said: "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."

I believe this is an alternative to my suggested method. You can indeed go through all the steps methodically, but to me, it's a lot easier to quickly check all the Ta caps in a plug-in, than it is look through the manual, determine which supply has the problem, identify the parts, and trace the power buses through the actual circuitry. I've been there and done that - it's a PITA, which is why I came up with my random direct search method. You know in advance what you're looking for, and it's easy to identify and poke around and check dozens of caps in less time (at least for me) than it takes to search around the manual and figure out where to start.After you've found the culprits, then you go to the manual and figure out what's what for replacement parts. You don't even need the schematics, and you don't have to care about which supply is affected - it's all about simply and quickly finding the bad caps, which are mostly right in front of your eyes, only an ohmmeter check away.

Try it both ways and see.

Ed


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

Jim Ford
 

I second the +/-15 V recommendation.   Had an S-4 sampling head with -15 V shorted by a bad Ta cap, and it brought the mainframe to its knees before I found and replaced it.  I'd recommend at least a 35 V rated cap for replacement.   Good luck!         Jim Ford                                        Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------From: "Ed Breya via groups.io" <edbreya=yahoo.com@groups.io> Date: 2/7/21 11:41 AM (GMT-08:00) To: TekScopes@groups.io Subject: Re: [TekScopes] Tektronix 7b92a shuts down crt & graticule illumination on 7904 mainframe 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: Spectrum analyzer Tektronix 7L13 on mainframe Tektronix 7603

Ed Breya
 

OK, Attilio, here you go:

I looked at the LO drive circuits and circuit descriptions and calibration info in the TR503 and TR502 manuals. I think you've been hung up on this 2LO BPF adjustment issue, where you're manually driving the LO with an external supply. Forget about that for now. You don't need to redesign the circuits to get higher tune voltage - it's already capable of reaching around 17 V, maybe a little more, which hopefully is plenty enough. At the plus extreme, U365A's output should rail at somewhere around +18 V or so (you should look up the NE5558 specs to see just how high it can get), since it's powered from +20 V. Q420 and the current limiter should drop about a volt, so the output will be able to get to around +17 V, and intrinsically limited there. Q445 and Q430 form a search oscillator to make sure the tune voltage sweeps around until phase lock is achieved, but apparently only kicks in if the tune voltage drops below +3 V. In the BPF tuning procedure with external supply drive, it says something like "do not exceed 20 V," so the capability of the circuit is within the limit.

In your test setup, you already have the PLL open-loop since you've run the IF into the counter, and the PLL tune voltage is disconnected. So, using your current setup, with the LO powered from the +15 V external supply, and measuring about 2095 MHz on the counter, check the PLL output tune signal with a scope - it should be either stuck high near 17 V, or sweeping up and down between there and some low value around a couple volts.

If it's stuck near 17 V, then that's perfect, just what you want for the next step. Now shut everything down and disconnect the external supply, and reconnect P446 so the PLL will run the LO. Fire it up and observe the frequency on the counter - it should be stable and well above 2095 MHz. Continue to monitor the tune voltage on the scope, and make sure it's still up around 17 V, not sweeping. If it is sweeping, then disable the search oscillator by grounding Q445's collector. You should now see the maximum tuning frequency available, on the counter. Hopefully, it will have a comfortable margin, maybe 2100 MHz or higher. If so, then shut down again, and hook everything back up to normal, and connect the 2LO from the 7L13. Continue to monitor the tune voltage. Fire it all up, and see if the PLL locks, indicated by the tune signal being constant, somewhere near +15 V. If it is, then you've lucked out, and the 2LO BPF is close enough to get a good signal through, the IF and PLL are working, and the LO is running around 2095 MHz. The rest is then a matter of perfecting the changes and tweaking it up. At this point it would be good to shut down, and solder an 18 V, 1 W, 5% Zener diode onto the LO's power supply/tune connection, from there to ground, to serve as an absolute clamp around +18 V. It will also provide reverse voltage protection. The physical location can be at the module (best) or wherever convenient, as long as it's on that line, and can't be disconnected accidentally. This will give some protection against accidents during any situations where external driving is used - later during tweaking - or if a failure in the tune driver (like if Q440 were to short) lets it go over-voltage.

Whether this all works, or doesn't, please report the results, and we'll see what to do next. Good luck.

Ed


Re: Help for DC503A universal counter repair

Attilio
 

Hi everyone,
I have isolated the "Blanking" output from U1520 (pin 11), obviously the non-significant zeroes remain on (visible on the display), but in this way the frequency meter works well and the display remains on. But there is a second problem, FREQUENCY, all AVG functions and TIME MANUAL work OK while instead the PERIOD B, WIDTH B and TIME A - B functions do not work.

Do you have any advice for the repair.

Thanks for the attention.
-- Cheers
Attilio


Re: 576 serials

Eric
 

Mine was a change from -02 to -03. The transformer cot warm over current
and the power supply collapsed do you know if I register change is
nessessary from 02 to 03?

On Sun, Feb 7, 2021, 5:17 PM Dave Brown <davebr@modularsynthesis.com> wrote:

The 576 mod summary shows the new 120-0612-03 transformer was implemented
for serial number greater than B089999. It required two resistors to be
changed. The field mod notice is dated June of 1983.






Re: 576 serials

Dave Brown
 

The 576 mod summary shows the new 120-0612-03 transformer was implemented for serial number greater than B089999. It required two resistors to be changed. The field mod notice is dated June of 1983.


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.







Scanned by McAfee and confirmed virus-free.
Find out more here: https://bit.ly/2zCJMrO


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

8521 - 8540 of 186401