Date   

Re: A Primer of Waveforms and their Oscilloscope Displays

Michael W. Lynch
 

I would be interested. This type of material needs to be preserved whenever it is found. TekWiki is the perfect repository for this.

--
Michael Lynch
Dardanelle, AR


Re: TDS 684A needs recapping?

Ray
 

I got a tds694A, it had some ripple, super imposed on the waveforms so I recapped the power supply.The 684 and 694 are very similar, the powersupply is the same as far as I knowAnyways the ps electrolytic caps are all through hole.There is about 30 +- a few. 2 where bad. The rest I changed out to get better esr and have peace of mind.Get good quality, 105 deg rated and 5000 hr or better rating.Things got better but I wound up changing all tantalums on the aquisition board as well. Then I changed the tantalums on the output of the 3.3 v dc dc converter.The converter creates a lot of ripple on 3.3 and i am actually looking to replace it with a better, modern eqivalent.Your mileage will differ since the aquisition board is different.Another area will be the display unit.There are lot of caps in there as wellBtw I used a 45 years old weller wtcp solder iron to do all the work. Small tip for the smd tanatalums.Just use a needle nose to lightly pull on the smd caps body then heat one side and switch back and forth a few times and it comes right off. The through hole caps where actually the hardest to get out. Had to use solder sucker and or just steady heat and pull on thr cap and wiggle them out.RaySent from my T-Mobile 4G LTE device------ Original message------From: Rogerio ODate: Sat, Sep 12, 2020 09:07To: TekScopes@groups.io;Cc: Subject:[TekScopes] TDS 684A needs recapping?Hi,
I have bought a tds 684A at Ebay some years ago and it was working ok.
As soon as I received it I opened it up to check if there was some indication of leaking capacitors.
It seems it was assembled in 1994.
Since I could not find any, I closed the instrument.
Everything went well for some years but the instrument started to show some "flicker" on the display from time to time.
Also the data shown is wrong, so it seems I will have to change the NVRAM.
I have already posted a question about possible causes of this flicker and it was suggested that I checked the power supply (and/or all the caps in the unit).
Since I am afraid of damaging the boards replacing the SMD capacitors I have uploaded some pictures of the boards to get an advice about the need to replace them since all solder joint (in my opinion) show no indication of corrosion.
The album is "TDS 684A needs recapping?"
Would you please check the photos and give some advice about the need of replacement?
Concerning the NVRAM, I have read conflicting information about loosing the calibration if I replace it.
What is the current NVRAM model that I can buy?
There is a person selling a FRAM replacent for these scopes but the price is a little high for me ($100).
Any advice on this issue?
Thank you all.
Roger


Re: A Primer of Waveforms and their Oscilloscope Displays

Tom Phillips
 

I'm interested too.
Thanks for bring the document to light.


Re: 2445 “A” sweep Issue

Siggi
 

Hey Chris,

it'd be mighty useful to see pictures of how your scope behaves, as I'm not
sure what "the start of the “A” sweep is off the CRT to the left" means. If
you input the calibrator signal to a channel and trigger on it, you should
be able to position the start of the sweep off the right and left edges of
the CRT as I recall. Does the horizontal position control work?
If you enable both A and B sweeps, do they start at roughly the same point
on the CRT?

Also note that the calibrator has a fairly precise frequency that adjusts
with the sweep speed you select to maintain 5 cycles of the square wave on
the CRT (up to point). You can therefore use the calibrator to assess
whether your sweeps are reasonably calibrated and whether they're linear.
Are they?
The 2445 is all drive by wire, where control voltages generated on the A5
board are used to set the sweep timing and the vertical gain of the scope.
The horizontal position control is one of those control signals, though it
should apply to both sweeps equally.
Sweep timing is also governed by control signals that are set through
calibration, so it's possible that some or all of your A sweep timings are
way off.

So far you're not giving us a whole lot of information to point you in
profitable direction though.

Siggi

On Thu, Sep 10, 2020 at 11:09 PM <christopherbath@hotmail.com> wrote:

Hi Siggi,

Thank you for your useful comments. The is a 2445 scope and not 2445A or
2445B.

I believe the scope has lost calibration data. The scope shows a failure
of Test 04. With a status of 11. Having a look at the service manual just
now I have found the following comment "If the bottom row of the readout
contains dots in the normally blank spaces, a wrong calibration constant
has been encountered. The instrument must be readjusted to remove the
incorrect calibration constant from the EAROM". This matches exactly with
what I am seeing on the CRT.

My suspicion is that the hybrid is working however I wanted to be sure as
the start of the “A” sweep is off the CRT to the left. I am assuming that
if the horizontal hybrid had failed then everything would have been to the
left.

The scope does seem to trigger. The Trigged LED illuminates when the Cal
signal is applied and trigger level adjusted.

Can the loss of the calibration constants result in the “A” sweep being
“lost”?

Thanks,

Chris








Re: A Primer of Waveforms and their Oscilloscope Displays

benwetzel
 

I would also be interested sir.


535 on CL

Bert Haskins
 


4 photos uploaded #photo-notice

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

The following photos have been uploaded to the TDS 684A needs recapping? album of the TekScopes@groups.io group.

By: Rogerio O


TDS 684A needs recapping?

Rogerio O
 

Hi,
I have bought a tds 684A at Ebay some years ago and it was working ok.
As soon as I received it I opened it up to check if there was some indication of leaking capacitors.
It seems it was assembled in 1994.
Since I could not find any, I closed the instrument.
Everything went well for some years but the instrument started to show some "flicker" on the display from time to time.
Also the data shown is wrong, so it seems I will have to change the NVRAM.
I have already posted a question about possible causes of this flicker and it was suggested that I checked the power supply (and/or all the caps in the unit).
Since I am afraid of damaging the boards replacing the SMD capacitors I have uploaded some pictures of the boards to get an advice about the need to replace them since all solder joint (in my opinion) show no indication of corrosion.
The album is "TDS 684A needs recapping?"
Would you please check the photos and give some advice about the need of replacement?
Concerning the NVRAM, I have read conflicting information about loosing the calibration if I replace it.
What is the current NVRAM model that I can buy?
There is a person selling a FRAM replacent for these scopes but the price is a little high for me ($100).
Any advice on this issue?
Thank you all.
Roger


Re: A Primer of Waveforms and their Oscilloscope Displays

Richard in Edenton NC
 

Me too please. That's one I have not seen before.

73 Richard W4MCD


2247A Counter/Timer Calibration question

tekscopegroup@...
 

Yesterday I turned on my 2247A and it immediately went into self cal and then reported a problem with the backup battery. I replaced that battery back in 2012 with a fresh one from BatterySpecialists.com, as the original one was already dead when I first got the scope. I thought its weird that the replacement barely lasted for 8 years. Guess they don't make them as they used to? I don't recall checking the date of manufacture of the first BR-2/3 replacement, or if it even had one at all, but will definitively check again when it comes out, and also record the date on the new replacement BR-2/3.

Anyway while I am going to go into the scope wanted to touch up a couple of things, like the step balance on the lower ranges, and the Counter/Timer calibration which I had noticed for some time now that it was consistently off by about 70Hz for a couple of years now, when compared to my rubidium oscillator, and which I know is dead on 10MHz as measured with another calibrated counter.

So according to the 2247A service manual (070-6367-00, page 5-15 / 147) it says to set the scope counter/timer to measure frequency, connect a TG501 set to 1uS time markers, which should be equivalent to a 1MHz signal. It then instructs to adjust C1904 (10MHz internal time base cal) "for a frequency readout on the scope between 999.994,10 and 999,995,10 KHz (0.999,994,10 to 0.999,995,10 MHz)".

My question is, why if I am using a signal of exactly 1MHz, do I have to calibrate the time base slightly lower? I would think that one would want to calibrate to match an exact reading of 1,000,000 instead. Can anyone shed some light on this? BTW the procedure as usual instructs the calibration to be done after warming up the scope for at least 30 minutes, so drift would be at a minimum when doing the calibration, and so I would assume that calibrating for a slightly lower frequency readout would not be related to initial cold start drift compensation. Or is this perhaps done for some long term drift compensation?

So why not calibrate dead on to the input signal frequency?


Re: A Primer of Waveforms and their Oscilloscope Displays

Glydeck
 

I would love to read that.

George

On Sep 11, 2020, at 10:15 PM, sdturne@q.com wrote:

I figured this might be of interest to the group. I found this little Tektronix pamphlet for sale at an ebay seller while I was looking for vintage -hp- catalogs. I couldn't pass it up. It dates from ca 1958 and the styling certainly echoes 1950s. While the technical content may not be of much use to the experienced oscilloscope user, I reckon this is the sort of material that field engineers could hand out to new or interested buyers.

https://groups.io/g/TekScopes/album?id=253524

If there is interest, I would be willing to scan this to put on TekWiki.

Sean



A Primer of Waveforms and their Oscilloscope Displays

Sean Turner
 

I figured this might be of interest to the group. I found this little Tektronix pamphlet for sale at an ebay seller while I was looking for vintage -hp- catalogs. I couldn't pass it up. It dates from ca 1958 and the styling certainly echoes 1950s. While the technical content may not be of much use to the experienced oscilloscope user, I reckon this is the sort of material that field engineers could hand out to new or interested buyers.

https://groups.io/g/TekScopes/album?id=253524

If there is interest, I would be willing to scan this to put on TekWiki.

Sean


Re: Photo Mystery Tektronix? Item.JPG uploaded #photo-notice

 

On Sat, Sep 12, 2020 at 01:19 AM, Raymond Domp Frank wrote:


Isn't that a dummy module for the TDS2xx series of LCD 'scopes?
Just checked - it is. Not much use...

Raymond


Re: Photo Mystery Tektronix? Item.JPG uploaded #photo-notice

 

Isn't that a dummy module for the TDS2xx series of LCD 'scopes?

Raymond


Photo Mystery Tektronix? Item.JPG uploaded #photo-notice

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

The following photos have been uploaded to the Mystery Tektronix? Item album of the TekScopes@groups.io group.

By: ebrucehunter


Re: Help troubleshooting a 2710 SA

Jaap Rusticus
 

Hello George and Martin,

Jaap from the Netherlands here. I have several from this series of analyzers. I had to repair a 2715 power supply two months ago and was successful in that. During the repair I also took out all the boards and disconnected the CRT, the front panel board and the reference board. Already having found a bad component in the PWM part of the supply, the supply would not start. I then supposed it had to be loaded, so I connected a 5 ohms 5W resistor between ground and the +5V output. There it went, all was fine and the +5V could be adjusted. This was a 2715 that I transformed into a 2712.

I just measured the ripple voltage for you on the main filter cap in a simple way - analog voltmeter on AC with a 100nF series capacitor - and it showed about 5V on the meter. This is not peak to peak of course but the value gives you an indication.

I assume you know about the problems that can happen with the Display Storage board. My three 2710's all have this problem.

Please keep us informed about the progress of your repair.

Greetings, Jaap


Added album Mystery Tektronix? Item #photo-notice

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

ebrucehunter added the album Mystery Tektronix? Item: I received this item with a recently-purchased Tektronix printer. The seller apparently thought it went with the printer. Can anyone identify it? Bruce, KG6OJI


Re: TDS 68x Fan replacement

Rogerio O
 

That worked for me also.
Thank you very much!


Looking for a push-pull switched potentiometer.

Jared Cabot
 

Hi all.

I'm currently repairing my TM500 module TG501A which seems to have been dropped on its face in a previous life, and I need to repair the 100ohm potentiometer inside as the rod connecting the knob to the pot has damaged the switch section of the pot when it was slammed inwards during the unscheduled impact test.

Does anyone have a Tek part number 311-2351-00 potentiometer, or any other Clarostat brand pot that looks like the one in this photo?
https://i.imgur.com/GbbAHmu.jpg

I specifically need the 4-pin switch section at the rear to swap into my pot assembly, as these pots are modular and can have sections interchanged with the liberal use of a drill bit on the rivets holding them together to disassemble them, so the actual resistance value etc doesn't matter as long as it has the NO/NC switch section.

I have paypal funds standing by for anyone who can send a part to me in Japan.


Thanks!


Re: Test Fixture Name

Dick
 

Saw those and you are right, they are pricey critters.

Thanks, Dick, W1KSZ
________________________________
From: TekScopes@groups.io <TekScopes@groups.io> on behalf of Roy Morgan <k1lky68@gmail.com>
Sent: Friday, September 11, 2020 5:47 AM
To: TekScopes@groups.io <TekScopes@groups.io>
Subject: Re: [TekScopes] Test Fixture Name

Pomona Electronics has what you need. They are expensive but they are the best there is.

Not sure what they call them.

Roy Morgan
K1LKY Western Mass

On Sep 11, 2020, at 2:03 AM, John Gord via groups.io <johngord=verizon.net@groups.io> wrote:

Ed,
The Tek and Pomona boxes are similar (including color) but I don't think that Pomona made the Tek boxes.
...
The Pomona boxes have a textured finish and connectors secured by 4 screws each.
-

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