TDS7254B Signal Coupling Stuck at GND - Page 1
Forum section: electronics / repair

author: sprit
author_rank: Regular Contributor
timestamp: August 20, 2025, 01:59:22 pm
content: Hello everyone, have a nice day!I have a TDS7254B bought from a Flea market. It has a broken screen and a broken hard drive. After bringing it home, I cleaned it and did a preliminary test and found that it booted normally. Then I replaced it with a new screen and reinstalled the OS. Luckily I still had a backup of this model. But everything starts from here. After starting the tekscope app it shows waveforms in all 4 channels. I waited for the device to warm up and did user calibration and diagnostic, everything passed.But when I look closely, the scope is stuck at GND coupling, unable to switch to AC or DC. Do you guys know what this error is? I I have attached the photo below. All coupling options are greyed out as shown in the picture. Looking forward to your help.I'm wondering if the machine lost calibration data or not. I haven't checked the NVRAM battery to see if it still has power. Thank you very much. My English is not good so if there is any mistake, I hope you will forgive me.Sincerely,Feng

author: coromonadalix
author_rank: Super Contributor
timestamp: August 20, 2025, 02:14:21 pm
content: what fw / sw you put in it ?

author: sprit
author_rank: Regular Contributor
timestamp: August 20, 2025, 02:23:06 pm
content: hi coromonadalixi put the tds7404b image to it, sw ver 5.1.3

author: picburner
author_rank: Frequent Contributor
timestamp: August 20, 2025, 02:44:48 pm
content: "From the Menu bar, select Help->About TekScope" If you do this test, does the correct scope name and firmware appear?

author: sprit
author_rank: Regular Contributor
timestamp: August 20, 2025, 02:47:09 pm
content: hi picburnerIn the tek info menu, its appear right model and serial

author: picburner
author_rank: Frequent Contributor
timestamp: August 20, 2025, 02:53:50 pm
content: There are two versions of the same firmware, I wanted to check that you loaded the right one.So the problem is somewhere else.

author: calibrationfixture
author_rank: Regular Contributor
timestamp: August 20, 2025, 03:34:19 pm
content: Hi sprit,A CSA/TDS7000(B) and TDS6000(B/C) without TCA-Adapters on its Ports is always grounded. You can't switch between GND and DC (50R Terminated). With a TCA-1MEG Adapter you can switch between GND, AC and DC.Calibrationfixture

author: sprit
author_rank: Regular Contributor
timestamp: August 20, 2025, 03:43:48 pm
content: Thank youuuuu. I thought it was faulty, turns out it needs a TCA jack to work, I thought the mobo was faulty. I don't have that TCA jack on hand, I'll order a few and try them later. Thank you, thank you so much. That makes me feel much better. I must have misremembered that with the old TDS7104 it could detect the input and change it. I thought this 7000B would too. Thank you very much.

author: sprit
author_rank: Regular Contributor
timestamp: August 20, 2025, 03:46:39 pm
content: By the way I'm uploading a backup of this model, will have a download link soon. Just hope no one reports my drive account lol.

author: coromonadalix
author_rank: Super Contributor
timestamp: August 20, 2025, 04:41:02 pm
content: if you had or have a chancecheck the mobo capacitors, and yes the famous nvram battery, once it really dies you'll loose the scope functionality, since the power pc board will be brain washed ...you have a console port idc connector, you could connect and backup / copy the settings, there are some nvram export scripts in the huge tds7k threaddo theses backups too while the scope works ... as well as your hdd as you said you would dofor some boot speed upgrades there are some ide ssd with no trim support.do checks all the fans and mostly under the scope, the big acq / analogic board to gently remove any dust accumulation, and you could check the trigger chips and maybe add some small heatsinks on them, they heat a lotat some point you can upgrade the cpu and ram qty, it will help a bit, but mostly do a good clean up in windows for any non related / started services / applications / crap removal would help a bit toothe only problems i have on our tds7254b we are not able to calibrate the touch screen ?? we are slightly off a bitsometime you may snatch some tca adapters on ebay, we have the bnc / sma ones

author: calibrationfixture
author_rank: Regular Contributor
timestamp: August 20, 2025, 05:31:12 pm
content: Hi sprit,The Scripts to which coromonadalix refers to are at:https://www.eevblog.com/forum/testgear/tektronix-tds6000b7000b-series-nvram-dump-script/Contrary to the CSA/TDS7000 Non-B's all Trigger Chips in the B-Series are more substantial and have big Factory installed Heatsinks.Calibrationfixture

author: calibrationfixture
author_rank: Regular Contributor
timestamp: August 20, 2025, 05:54:31 pm
content: @ coromonadalix,When you minimize the Scope Application the Windows Start Menu normally unveils a Touch Screen Calibration Program (also the TekConnect Adjust feature in case this Software is installed).Calibrationfixture

author: sprit
author_rank: Regular Contributor
timestamp: August 21, 2025, 05:41:56 am
content: Hello everyone, have a nice day.Here is a link to my TDS7404B backup in case anyone needs it. The backup was done with Terabyte imager software.Link GG Drivehttps://drive.google.com/file/d/1TnzH0W40DAz7-lC_tM4i1hs6xF4IPSN1/view?usp=drive_link

author: sprit
author_rank: Regular Contributor
timestamp: August 21, 2025, 05:47:31 am
content: Hi calibrationfixture,I was wondering if I could bypass the need for the TCA jack so the scope would work properly? What is the actual connection that Tektronix calls TCA called? I mean does it have another name or is this a Tektronix proprietary interface and I can't find something else to fit in that little hole?Thank you

author: calibrationfixture
author_rank: Regular Contributor
timestamp: August 21, 2025, 06:08:07 am
content: Hi sprit,To limit the investments I should look for one TCA-BNC Adapter. Then you can also use the same Active Probes (P6243 e.a.) as for the TDS7054/7104 and TDS5000(B) Series.The Special Connector Tektronix uses for the TCA Ports is called BMA. This is Signal only. The Pogo Pinned Data/Power-Interface is another story. LeCroy uses a similar Interface.https://www.eevblog.com/forum/buysellwanted/wtb-tektronix-tekconnect-female-connector/msg5688883/#msg5688883Calibrationfixture

author: sprit
author_rank: Regular Contributor
timestamp: August 25, 2025, 02:59:50 pm
content: Problem solved. It was just me not connecting the TCA adapter. Thanks a lot calibrationfixture for the advice and everyone else. Wish you all good health and peace.Sincerely,Feng

author: coromonadalix
author_rank: Super Contributor
timestamp: August 25, 2025, 04:51:07 pm
content: just tried on our 7254b i confirm this behaviour without any tca adapter