Tektronix TDS654c noise with higher sampling rates

[gabornemeth2013]

Greetings.

I have recently acquired a tektronix TDS654c oscilloscope, where I have found that everything works fine, with sampling rates under 25Msps, but once I go up to 25M, there is a periodic noise appearing on the signal, regardless of being in AC/DC/GND coupling, which looks to be around 250Khz. I have found online that this could be caused by a bad cap, so then I went ahead and replaced all the electrolitic caps in the PSU, which unfortunately didn’t solve the issue. I believe that this still could be a PSU issue (periodic noise suggests that), and hopefully not with the acquisition board. So this is where I’m stuck however, maybe a forum member has seen this issue, or could someone point to the right direction? Any help would be appreciated.

I have attached a photo of 10 and 25 Msps acquisition.

Thank you,
G

[sicco]

Does this model have SPC (signal path compensation) as an option under Util/Calibrate menu? If yes then see if that passes ok. Quite likely that after a pass your ‘noise’ will be gone. The noise then was systematic errors, scale or offset, in the many elements in the array of sample/hold elements in the ADC chips.

[gabornemeth2013]

Hi!

That did solve my issue, I could try it yestersay! I didn't even know about this feature, thank you for helping me!