Tektronix TDS350 Calibration Error NVRAM changed - Page 1
Forum section: electronics / repair

author: slowolitus
author_rank: Newbie
timestamp: October 21, 2018, 07:52:26 pm
content: Hello everyone!I have Tektronix TDS350 oscilloscope with Cal Initialization fail message after power up.NVRAM was changed with new one (filled with "FF"s) but after first power up a have a bunch of save/recall memory errors in Error log and if I perform voltage calibration (witch Fluke 715 calibrator) it ends always with "Cal error, CVR source gain"...But a new NVRAN ds1630 seems to be working fine because the number of power ups and an error log will be not lost after full power off.The both channels shows the waveforms on the display normally.There is no smd caps in this model witch could dry out with the time.Please respond who faced the same problem or if you know that doese it mean "Cal error, CVR source gain" and why there is a memory error if NVRAM works fine. Maybe this error is not caused by NVRAM...Maybe someone has a working dump for ds1630 for this model, then I could flash it and attempt to recalibrate the scope.Thank you in advance and sorry for my english, I am from Germany an my native language is Russian.

author: Samogon
author_rank: Frequent Contributor
timestamp: October 22, 2018, 04:06:29 pm
content: Well calibration data is nonexistent, you have to calibrate scope in order to record new, if you didn’t preserve original

author: Hexley
author_rank: Regular Contributor
timestamp: October 24, 2018, 12:33:14 am
content: Just checking -- did you remove the Cal Jumper J609 from the main board? It appears that it protects the calibration settings if installed.See Figure 6-19 in the TDS 350 Service Manual, page 6-36 for more info.

author: hardcoreman
author_rank: Contributor
timestamp: October 24, 2018, 07:59:32 pm
content: btw. on fluke 8840 with new cal. memory, i must run erase cal memory from cal. menu and then cal mem error disapeared. and after that i make full calibration.

author: slowolitus
author_rank: Newbie
timestamp: October 28, 2018, 11:03:12 pm
content: Samogon, it fails after first calibration step described in manual... with "Cal error, CVR source gain" and I don´t really understand what does it mean...Hexley, yes I removed it. If not you can´t enter in calibration menue at all.hardcoreman, I have installed new empty NVRAM and it is calibration memory, so it should be erased.I have checked the relays in first channel by applying 5V signal with 40mA current limitation, so all relays are OK...In the service manual there is no instructions about what user should do after changing NVRAm memory chip.If someone changed NVRAM in tektronix scope please tell me about your experience.

author: zainka
author_rank: Newbie
timestamp: October 31, 2020, 10:36:34 pm
content: HelloI know its some time since the last post but did you succeed to fix this issue? I am about to do a NVRAM replacement on my TDS350 (new generation with S/N > B030100) but as you I have no binary-image to load into the new nvram before replacement. But I have a lot of issues and no visual damage to start on but the problem lays on the main board and NVRAM is one of the problem.Do you by any chance have the schematic? The service manual I have only have block schematics.I might get my hand on a TDS350 with intact memory which, if lucky, i am able to dump memory from before it is corrupted aswell, (maybe by offering a replacement chip to the lucky owner).BregZainka

author: Labrat101
author_rank: Unknown
timestamp: November 01, 2020, 07:11:20 pm
content: Hi I had the same error after I refurbished my TD340 .The only way is to remove the Cal jumper and then restart .there is now another option on the calibration setting .you will have to go though the whole sequence of cal its a little tricky took me about an hour.Follow the instruction in the service manual .you will need a digital voltmeter 4 place decimal.a DC volt source that can supply -6v to +6 stable .& a signal Gena 50 ohm though load . Tee's and patch leads , and a BNC banana pluglarge cup of coffee and a quite hour .All the instruction are displayed on the screen .you must have the 50 ohm connected during the entire operation or it will fail.also remember when it asks for say 1v you have to set your source to 2v.same as when the minus are requested .all source voltages must be compensated for 50ohm . or double all voltages onthe source . and it will pass .

author: zainka
author_rank: Newbie
timestamp: November 01, 2020, 08:19:11 pm
content: Thank you, I have all the equipment available so that should not be any issue. I have the jumper removed but the strange thing is that the CAL menu is available regardless off the jumper setting (measured the jumper and it is ok). I hope that does not indicate issues with the CPU not reading I/O as it should. I also noticed an different issue with the Acq (acquisition memory) which fails. This is the DRAM and it needs replacement, Service-manual calls for a main board replacement for such issues but I give it a try repairing it.. I have purchased one TC514260BJ-70and will have it replaced when arrived. It will take some time but hopefully it will work.By the way, I do not drink coffee, I hope a cold beer or cola will do..Meanwhile I also have a 54601A with trigger issues to keep me busyThanksVidar

author: Labrat101
author_rank: Unknown
timestamp: November 01, 2020, 09:07:16 pm
content: You must remove the jumper .. with the jumper on you can see the cal but that is all.Must remove the jumper .and keep a 50ohm terminator connected at all times during cal . follow the intrusion on the screen.and remember to put twice the voltage ask for to compensate for the 50.ignor the errors you have after the cal has completed without any errorsit will boot correctly . take your time the voltages must be exactA cold beer will do fine but don;t get drunk or you will see wavy linesupdate I hope the manual helps .

author: jpdesroc
author_rank: Newbie
timestamp: May 08, 2021, 12:28:47 am
content: Quote from: Labrat101 on November 01, 2020, 07:11:20 pmI don't understand the doubling of the DC voltage source or not regarding the 50 ohms termination..For example in the voltage calibration process,if the calibration ask for 1 volt and I'm connected directly to a 'through 50 ohms' adapterto channel#1 why set the external power supply to twice this voltage (2 volts)while the BNC voltage is at 1 volt ?I'm loosing it here..

author: Labrat101
author_rank: Unknown
timestamp: May 08, 2021, 07:10:35 am
content: Quote from: jpdesroc on May 08, 2021, 12:28:47 amI posted a complete how to do it and why here..https://www.eevblog.com/forum/repair/upgraded-tds340-to-tds360-200mhz-1gsas-for-any-one-interested/msg3425856/#msg3425856I know there are some difference between the 340 & 350 . but the calibration is basicly the same ..You must give the scope 1v after the 50terminator so the scope see 1v and Not 0.5v .If you have the correct Tek scope calibrator that does the corrections for the 50 ohm .But I guess you don't so you have to double the voltage apx . I showed howto in the link with pictures .the voltage must be set correct before applying it to the scope .https://www.eevblog.com/forum/repair/upgraded-tds340-to-tds360-200mhz-1gsas-for-any-one-interested/msg3425856/#msg3425856