Author Topic: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair  (Read 26691 times)

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Offline EEVblog

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EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« on: January 01, 2014, 01:11:35 am »
Dave tries to find out what's wrong with a Tektronix TDS3054 500MHz 4 channel oscilloscope.
SPOILER: there is no ending...
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« Last Edit: January 01, 2014, 01:13:06 am by EEVblog »
 

Online mikeselectricstuff

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #1 on: January 01, 2014, 01:36:33 am »
"Distributed element filter" at 18:30 looks more like it's a laser-trimmed part (R or cap/inductor array)  - you can see the laser cut-line on it
 
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Online mikeselectricstuff

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #2 on: January 01, 2014, 01:45:43 am »
Would at least be worth probing around that diff output & comparing to another channel with the same input.
Also try heating & freezing, and flexing the PCB a little
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Offline Vgkid

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #3 on: January 01, 2014, 01:46:13 am »
Thanks for the upload, the maxtek marked chips in the hybrid are rather interesting. It appears that Maxtek(now Infinicon) only manufacturers instruments relating to thin film deposition, and various quartz based sensor assemblies.
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Offline gxti

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #4 on: January 01, 2014, 01:59:06 am »
Sample memory would be a good guess. When you have billions of cells made as cheaply as possible and bought on the commodity market it's no surprise that RAM is often the first thing to fail in a computer. That said, from the zoomed in look at the noise it doesn't look much like a single bit error.

I was also going to suggest probing the hybrid output but Mike beat me to it.
 

Offline free_electron

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #5 on: January 01, 2014, 02:01:49 am »
Maxtec was a spinoff of Maxim.
Maxim for a long time made some custom asics for tektronix. They were eventually borged by Tektronix hence the MaxTec name.

Tek spat em back out after the danaher borging and part of it went back to Maxim.

The hybrid contains Ac/Dc gnd and attenuator relays. the maxtec has an amplifier and divider chain ( voltage divider)

the Maxtec chip also splits the signal in a HF component and LF component. From the signal corruption it looks like the problem is in the HF section as the lf signal is perfect.
I would reflow the analog devices ADG361 square chip of that channel. at 25:58 you see the two differntial pairs. one is hf the other lf. check the pins inbetween. one of the rails may be gone. they are fed using ferrite beads.


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Offline kxenos

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #6 on: January 01, 2014, 02:12:29 am »
Dave, if you probe the differential output of the hybrid would it be possible to see if the problem is already there?
 

Offline EEVblog

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #7 on: January 01, 2014, 02:15:58 am »
the Maxtec chip also splits the signal in a HF component and LF component. From the signal corruption it looks like the problem is in the HF section as the lf signal is perfect.

Interesting, thanks.

Quote
I would reflow the analog devices ADG361 square chip of that channel. at 25:58 you see the two differntial pairs. one is hf the other lf. check the pins inbetween. one of the rails may be gone. they are fed using ferrite beads.

No ferrite beads in sight.
 

Offline Jay_Diddy_B

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #8 on: January 01, 2014, 02:22:13 am »
Hi,
I would guess that the front end is o.k.

What happens if you move the trace up and down the screen?

I would guess that there is something wrong after the ADC. I have seen similar displays on TDS5xx series if there is a bad connection in the acquisition memory.

Regards,

Jay_Diddy_B
 

Offline free_electron

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #9 on: January 01, 2014, 02:30:04 am »
backside board… actually side facing the front panel.

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Offline Hydrawerk

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #10 on: January 01, 2014, 02:43:12 am »
Well, the TDS3054 internal construction is not solid... For such an expensive scope (even today) i would expect more steel parts... Compare it to the DSOX2000, that is full of sheet metal.

Or even Tektronix MDO4000 series.
« Last Edit: January 01, 2014, 02:45:44 am by Hydrawerk »
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Offline david77

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #11 on: January 01, 2014, 03:25:37 am »
I have no idea what I'm talking about, but from the video it seems to me that only the positive side of the signal is affected by that weird noise.
So I'm left thinking could it  be some issue with biasing/decoupling of something in the front end? Maybe a dead cap or a very noisy power rail?

Seeing as what people still pay for these scopes on ebay it is probably even worth your while to look a bit further.

I guess a proper manual is not available for this machine, right?
 

Offline EEVblog

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #12 on: January 01, 2014, 04:03:49 am »
backside board… actually side facing the front panel.

There are only 4 SMD ferrites on the whole board, all under the 5th chip between the ADC's, and they test fine.
 

Offline NiHaoMike

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #13 on: January 01, 2014, 04:14:05 am »
I was once assigned a 12GHz Agilent scope to use for testing. There were many problems with it, as in one channel would not properly recognize active probes, another channel was completely dead (flat line), and yet another channel was noisy. They just swapped out the scope for a new one and I never heard what was wrong with the old one.

Try tapping the board with a pen or other plastic object to see if it's an intermittent connection.
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Offline EEVblog

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #14 on: January 01, 2014, 04:24:16 am »
Just shot a Part 2 video on this.
No surprises for guessing the outcome...
 

Offline member_xyz

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #15 on: January 01, 2014, 04:52:55 am »
I find it frustrating to watch your fault finding/repair videos.
Initial mechanical inspection and some speculation is OK to a certain point, but don't go overboard.
I don't kow why you avoid using electronic test equipment to do at least some basic measurements?
You have a multi channel scope, you could easily do some signal comparisons on the front end.
At the end of the day it may not resolve the issue, but for **** sake you are running en electronics blog/forum.








 
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Offline calexanian

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #16 on: January 01, 2014, 05:01:49 am »
I find it frustrating to watch your fault finding/repair videos.
Initial mechanical inspection and some speculation is OK to a certain point, but don't go overboard.
I don't kow why you avoid using electronic test equipment to do at least some basic measurements?
You have a multi channel scope, you could easily do some signal comparisons on the front end.
At the end of the day it may not resolve the issue, but for **** sake you are running en electronics blog/forum.


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Offline TooOldForThis

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #17 on: January 01, 2014, 05:32:05 am »
What does the channel look like in single sweep mode?  If there is any sign of a changing signal when no new data is flowing into the sample memory, then the problem must be in the sample memory or display logic.
 

Offline taemun

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #18 on: January 01, 2014, 05:57:50 am »
The waveform disappearing seems to be linked to the acquisition speed (SPS). At 5:20, you go into the Acquire menu, and on "Normal" horizontal resolution, you're pulling 10MSPS (look at the bottom right), and it has a display, and then "Fast" is 500kSPS, which doesn't have a display. At 5:25 you increase sample rate to 5MSPS (10us/div @ "Fast") and that has a display again.

At 5:54 it works on "Normal" down to 5MSPS (200us/div @ "Normal"), then dies below that.

I'd guess that something changes mode below 5MSPS.
 

Offline Kryoclasm

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #19 on: January 01, 2014, 06:13:10 am »
Pull hybrid 3 & 4 and plop 4 in 3's spot. 

That will confirm or eliminate that part of the board.

PITA, but would be interesting to see.  :o
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Offline Eliminateur

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #20 on: January 01, 2014, 06:13:28 am »
Dave, if you probe the differential output of the hybrid would it be possible to see if the problem is already there?
same thing i was thinking, why not probe the diff output when fed with the test signal and compare it to the same output from one of the good channels?, it might help pinpoint the problem better.
You could also probe the rest of the pins as well and compare
 

Offline taemun

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #21 on: January 01, 2014, 06:16:17 am »
Pull hybrid 3 & 4 and plop 4 in 3's spot. 

That will confirm or eliminate the part of the board.

PITA, but would be interesting to see.  :o


Or maybe probe the outputs first. Noise as on the display would be super easy to see, surely. The EEVblog slogan isn't "don't probe it, solder it mindlessly!".
 

Offline georges80

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #22 on: January 01, 2014, 06:38:59 am »
Well, if google has anything to say:

http://www.seekchip.com/icstock-m/MM9576-VJG.html

Implies those aren't ADC chips but some kind of fancy fifo/ram controller.

My 'guess' is that the maxtek chips would have the adc (or equivalent) - I'd assume one would keep all the analog stuff on the hybrid module versus trying to feed it down to the 'digital' board.

The MM9577 again, if you believe google:

http://www.seekchip.com/icstock-%EF%BC%AD/MM9577-ACE.html

is an ADC (not very fast).

Good luck :)

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Offline Maxlor

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #23 on: January 01, 2014, 06:41:12 am »
I find it frustrating to watch your fault finding/repair videos.
Initial mechanical inspection and some speculation is OK to a certain point, but don't go overboard.
I don't kow why you avoid using electronic test equipment to do at least some basic measurements?
You have a multi channel scope, you could easily do some signal comparisons on the front end.
At the end of the day it may not resolve the issue, but for **** sake you are running en electronics blog/forum.
Yeah... as a software engineer, the random poking around kind of makes me cringe. The term we use for that is shotgun debugging. My approach would be to use bisection to find the problem area. In this instance, you've guessed at what some of the traces on the boards do, let's probe them with a scope at various points to see whether the fault exists before or after that point. Why waste time with random wild shot guesses.

On the other hand, since Dave is commenting on the various bits and pieces he examines as part of the random wild shot guesses (Dave: hey, at least they appear that way in the video. If you've done a more methodical problem analysis, it's not in the video. If I've stepped on your toes here, I'm sorry :) ), I find the video interesting to watch. There's still so much I don't know, and what might be an off-hand side comment to you is really an information nugget to me.
 

Offline EEVblog

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Re: EEVblog #564 - Tektronix TDS3054 Oscilloscope Teardown Repair
« Reply #24 on: January 01, 2014, 06:41:19 am »
I don't kow why you avoid using electronic test equipment to do at least some basic measurements?
You have a multi channel scope, you could easily do some signal comparisons on the front end.
At the end of the day it may not resolve the issue, but for **** sake you are running en electronics blog/forum.

Because:
a) That's what you do first
b) The video was already long enough
c) A ran out of time (it was new years eve)

Now, I could have not uploaded the video, and kept it until I had finished the repair or done some more stuff, and that's how some bloggers do repair videos. But that's not how I do it. I shoot some content and I upload it, even if it's not finished.
I have already shot a part 2 that does that stuff, and once again I have ran out time to finish it off (new years day + other things to do), but I'm ging to upload that, still an unfinished repair.
 


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