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Electronics => Repair => Topic started by: ragge on December 29, 2019, 11:03:27 pm

Title: Tektronix TDS 694C - noise on input channels
Post by: ragge on December 29, 2019, 11:03:27 pm

Hi all,

I have a Tektronix TDS 694C with noisy input channels.
The examples below are with nothing connected to the inputs.
In 5 GS/s / 10ns/div mode, there is some 25 ns / 40 MHz cycles showing.
In 10 GS/s mode, it shows as some 5 GHz noise.

The input channel scaling does not seem to matter, the noise is pretty constant in amplitude on screen independent of voltage range.

Has anyone else seen this?
Could there be a problem with some power feed, or something?

The triggering only works on channel 1 & 2 on this scope. I have not yet tried moving the trigger chips around. Could those have anything to do with it?

Thanks for any hints, help and/or information!

Also, any pointers to repair information for this scope, and/or firmware never than v6.4e, would be much appreciated!

Best regards,

Ragnar

(https://www.eevblog.com/forum/repair/tektronix-tds-694c-noise-on-input-channels/?action=dlattach;attach=898930)

(https://www.eevblog.com/forum/repair/tektronix-tds-694c-noise-on-input-channels/?action=dlattach;attach=898934)

Title: Re: Tektronix TDS 694C - noise on input channels
Post by: nctnico on December 29, 2019, 11:11:57 pm

Make sure to run the SPC first. This might clear the problem.

Title: Re: Tektronix TDS 694C - noise on input channels
Post by: ragge on December 30, 2019, 05:02:45 am

Dear nctnico,

You were entirely right, an SPC solved it!
I had no idea that the signal could be this broken just because of bad self calibration.
I am most grateful and embarrassed at the same time. :-)

Best regards

Title: Re: Tektronix TDS 694C - noise on input channels
Post by: madao on December 30, 2019, 05:37:17 am

Hello

Can you save  firmware ?  (i wanna play with TDS684C Aqcuisiiton board.)
 I can tell,  Firmware from TDS500/700 is not useable in  TDS600. 

TDS600 is  CCD based DSO, it is really sensitive by deviation of SPC constant.   

regards
matt

Title: Re: Tektronix TDS 694C - noise on input channels
Post by: ragge on December 30, 2019, 05:47:08 am

Hi,

The firmware for 694C actually says only "694C" in it, as opposed to e.g. the 5xx/7xx firmware that has a lot of models mentioned. I doubt it will work on a 684C.

There is 684B v4.3e at http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix/Tektronix_-_TDS5xx_TDS6xx_TDS7xx_Digital_Phosphore_Oscilloscopes (http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix/Tektronix_-_TDS5xx_TDS6xx_TDS7xx_Digital_Phosphore_Oscilloscopes), not sure if that will work with a 684C though.

Best regards
Ragnar

Title: Re: Tektronix TDS 694C - noise on input channels
Post by: KE5FX on December 30, 2019, 06:33:19 am

Quote from: nctnico on December 29, 2019, 11:11:57 pm

Make sure to run the SPC first. This might clear the problem.

Good call there, I would never have guessed that was an SPC issue.

Title: Re: Tektronix TDS 694C - noise on input channels
Post by: madao on December 30, 2019, 07:04:35 am

Quote from: ragge on December 30, 2019, 05:47:08 am

Hi,

The firmware for 694C actually says only "694C" in it, as opposed to e.g. the 5xx/7xx firmware that has a lot of models mentioned. I doubt it will work on a 684C.

There is 684B v4.3e at http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix/Tektronix_-_TDS5xx_TDS6xx_TDS7xx_Digital_Phosphore_Oscilloscopes (http://www.ko4bb.com/getsimple/index.php?id=manuals&dir=Tektronix/Tektronix_-_TDS5xx_TDS6xx_TDS7xx_Digital_Phosphore_Oscilloscopes), not sure if that will work with a 684C though.

Best regards
Ragnar

600B is too old.   600C is right.  694C or  684C, it doesn't play a role.  Newer Firmware (since B-Serie) has  acquisitionboard-autodetection. 644, 684, 694, it doesn't matter.

thanks
matt