Strange problem on tds3054b - Page 1
Forum section: electronics / repair

author: pasta2018
author_rank: Regular Contributor
timestamp: September 05, 2024, 04:20:38 pm
content: Recently i have got a tds3054b,it can pass selftest and spc.However, for each channel when vertical range is 1v/div or up,there is clutter ,each channel is the same. when the range is 500mV or below, it is ok. I checked the ±5V and ±15V is stable and correct.

author: pasta2018
author_rank: Regular Contributor
timestamp: September 05, 2024, 10:28:16 pm
content: I take some photo

author: inse
author_rank: Super Contributor
timestamp: September 05, 2024, 11:11:27 pm
content: Is the phenomenon also visible with 50Ohm termination enabled at the inputs?

author: pasta2018
author_rank: Regular Contributor
timestamp: September 05, 2024, 11:15:34 pm
content: yes，and AC/DC model also the same

author: pasta2018
author_rank: Regular Contributor
timestamp: September 06, 2024, 03:40:28 pm
content: sometimes，it can not pass spc. but selftest is always ok

author: inse
author_rank: Super Contributor
timestamp: September 06, 2024, 05:34:04 pm
content: Do you have a second scope to verify the supplies are also noise free?

author: sicco
author_rank: Regular Contributor
timestamp: September 06, 2024, 06:05:03 pm
content: Can you show screenshots with the time base in the nano seconds / div range?Does the scope level-trigger on these spikes? (trigger mode normal, level at halfway the highest spike level)Looks like an issue on the digital data bus in between the 4 ADC chips and the largest (MM9595?) chip. Corrosion / moisture / conductive dust bad soldered pin?Try local cooling / freeze spray at that area.

author: pasta2018
author_rank: Regular Contributor
timestamp: September 06, 2024, 11:45:13 pm
content: yes,the supply is ok

author: pasta2018
author_rank: Regular Contributor
timestamp: September 07, 2024, 12:25:32 am
content: yes,this is the triggered signal

author: sicco
author_rank: Regular Contributor
timestamp: September 07, 2024, 06:13:10 am
content: That seems to rule out that the problem would relate to the digital bus between 4 ADCs and MM9595.The 2.5V reference - is that showing any AC unrest?This reference also feeds a + and - 2.5V power rail that feeds the ADC chips and also the attenuator modules. Do those +/- power supply rails show any unrest relative to GND when looking at those with another scope?Some hints on what reference and power supply lines i meam inhttps://www.eevblog.com/forum/repair/broke-my-tds3000b/post#20.

author: sicco
author_rank: Regular Contributor
timestamp: September 07, 2024, 07:02:49 am
content: is this the same problem?https://www.eevblog.com/forum/repair/help-!-strange-issue-with-tek-tds3054b/msg4532654/#msg4532654https://www.eevblog.com/forum/repair/help-!-strange-issue-with-tek-tds3054b/msg4532654/#msg4532654Is it the same unit maybe?Do you also run same (quite old) firmware? Tried upgrading to version 3.41?

author: pasta2018
author_rank: Regular Contributor
timestamp: September 07, 2024, 09:05:40 am
content: A little different, for my scope,the four channel always display a same wave,the clutter appears randomly.

author: pasta2018
author_rank: Regular Contributor
timestamp: September 07, 2024, 09:07:41 am
content: I have upgrade to 3.41. when the clutter appear, I can here there is little low noise inside,but I can not distinct where it from

author: pasta2018
author_rank: Regular Contributor
timestamp: September 07, 2024, 09:36:35 am
content: I checked some voltage，2.562V3.302V-3.340Vare these all right?

author: sicco
author_rank: Regular Contributor
timestamp: September 07, 2024, 10:44:42 am
content: The “little noise inside” might be a hint that a power supply rail is overloaded?But could also be a hint that you have bad caps on those rails.There’s a bunch of TO220 linear voltage regulators, two do +5 and -5 for just the attenuator modules. Check with another scope if there’s ripple on these lines.The DC average voltages that you quoted say nothing about AC ripple amplitudes.Another thing to confirm: if you bypass the mains power supply, and inject 15VDC from a 3 amps capable power supply instead, rigth at the output of the mains power supply, is the problem still there?No battery pack inside?

author: pasta2018
author_rank: Regular Contributor
timestamp: September 07, 2024, 01:25:12 pm
content: when I power on, there is no clutter,after 2-3 minutes,the clutter began to appear.

author: pasta2018
author_rank: Regular Contributor
timestamp: September 07, 2024, 01:26:06 pm
content: maybe something wrong with MM9595