Tektronix 2445B calibration - Page 1
Forum section: electronics / testgear

author: flashthunder
author_rank: Contributor
timestamp: March 22, 2024, 03:13:27 pm
content: Hi all...I am looking for thoughts on programming the Dallas chip for a Tektronix 2445B. I know there are several posts on this subject however my mind is muddled with all of the moving parts, so here is my situation. I have completed the A5 leaky capacitor repair issue and have replaced some of the power supply capacitors. The scope seems to work fine once it is out of the startup error screen. On startup the error that I see is "test 04 fail 01" which I understand to be a calibrate error. Well, no surprise there as this scope is a 1991 build and the Dallas battery has never been replaced (when I display test 2 data I just see strings on the same data, 07F4 and F407) so I know the calibration data is gone. Here is what I am planning and I'd like to here some thoughts.1) I have received a new Dallas (Maxim) chip from Mouser (DS1225AD-200+) which I will be installing on a socket.2) I copied the Test 02 address/parameters from a working 2445B Youtube video (yes, I did indeed transcribe 256 locations...thank you kind Youtuber!).3) Using the copied parameters I created a .bin file.3) I purchased a V12.63 Original VGecu T48 (Tl866-3G) Programmer (which I am hoping will work). Using this programmer I will upload the .bin file to the new Dallas chip.I do realize that the calibration will not be correct for my scope. My thinking is that as long as there is calibration data present the scope should startup and pass the self test routines. For my purpose I am not concerned about calibration so long as it's close enough. I suppose that if I am not concerned about calibration I could just leave the old Dallas chip in place but this is something that I just want to do as I learn a lot in the process. Plus it is fun working on these old platforms as you can most often find manuals and parts and it would be a shame to toss it in the trash.I do welcome all thoughts/advise.Thanks!

author: MarkL
author_rank: Unknown
timestamp: March 22, 2024, 11:22:12 pm
content: I think your plan will work.You have the right offset for programming? If not:https://www.eevblog.com/forum/testgear/tektronix-2465b-oscilloscope-teardown/msg4750262/#msg4750262It sounds like you're already quite aware of the pitfalls of copying calibration data. I would still encourage you to try get through the calibration procedure once you prove the scope boots and is ok.When you boot the scope after only programming the cal values, the other areas of the NVRAM will likely have garbage in them. The scope may boot with bizarre settings which you can reset by exercising all the controls. You could try putting 0xFF in all non-cal locations, or maybe 0x00. That might work better than garbage.It would be good if there was an option to do a reset to factory defaults, but I don't see it. All I see is that EXER 08 erases all the saved setups.Good luck!

author: flashthunder
author_rank: Contributor
timestamp: March 25, 2024, 07:02:35 am
content: Thanks for your advise MarkL!I was successful with programming the new Dallas chip with the "exercise 02" data from a different scope. My error code is now "test 04 error 02" instead of "test 04 error 01" so I plan to take your advice and attempt the calibration process. Interestingly, when I removed the old Dallas chip and read it's contents the "exercise 02"data was all garbage but all (or most) other locations seemed to be populated with good data. I kept what ever data was in the chip and just added the copied "exercise 02" data to it.At any rate the scope is functioning as it did before but now with a fresh Dallas chip.Thanks again,

author: Miti
author_rank: Super Contributor
timestamp: March 25, 2024, 03:51:33 pm
content: I have a file that I extracted from my Tek 2445B before I replaced the RAM with an FRAM. I can attach it tonight if you want.

author: flashthunder
author_rank: Contributor
timestamp: March 25, 2024, 09:28:10 pm
content: Miti, thanks...I would love to compare your file with the one I currently have.

author: Miti
author_rank: Super Contributor
timestamp: March 25, 2024, 11:02:38 pm
content: Attached.Cheers,Miti

author: MarkL
author_rank: Unknown
timestamp: March 26, 2024, 05:27:17 pm
content: Quote from: flashthunder on March 25, 2024, 07:02:35 amGlad to hear the scope appears ok!I'm not sure what "good data" would look like on these systems. In addition to providing non-volatile storage, that chip is the only RAM in the system and the CPU uses it for run-time data storage. I'm sure it initializes some of it on each power-on, so perhaps you're seeing that. Like blocks of all 0x00?

author: flashthunder
author_rank: Contributor
timestamp: March 26, 2024, 11:15:12 pm
content: Miti, I programmed my Dallas chip using your file....the result was the same (fail 04 error 02) as the file I created using another 2445B "exercise 02" data. Other than than the question marks on the bottom of the screen and the obvious out of calibration the scope seems to function just fine. I believe my option is to do a complete calibration.Thanks for the advice and support!

author: flashthunder
author_rank: Contributor
timestamp: March 28, 2024, 09:48:54 pm
content: Has anyone tried a Dallas chip from Qservice with a basic calibration file already loaded? If I understand correctly their Dallas chip with the basic cal file will allow the scope to boot to normal mode (will not stop and display error message). Of course, the correct thing would be to perform a calibration...but if I could get my scope to boot to normal mode without the annoying question marks I could live with that. Any thoughts?

author: calibrationfixture
author_rank: Regular Contributor
timestamp: March 29, 2024, 07:01:02 am
content: Hi,Copying ALL Data from a good working 24XXB Scope into a fresh Dallas Chip should work with no problems. Done that before with a 2465BDM, which Dallas Chip was corrupt. I suspect a HW Issue, Most likely the Trigger-Hybrid as was the case with a serviced 2466BHD. Gives also ?'s between Scale Factors.Success,Calibrationfixture

author: flashthunder
author_rank: Contributor
timestamp: March 29, 2024, 10:47:31 am
content: Thanks Calibrationfixture...this scope sat unused for several years. Except for the calibration errors on boot-up it's a very functional scope, having been used very little over its lifetime. However, while it was in storage the Dallas chip battery died so any cal data has been lost. I don't believe it to be a hardware issue as everything functions fine, my only issue it the firmware related error message when booting up. I was thinking that using another scopes data was a viable solution and you are confirming that. I have tried loading another scopes file (thanks Miti) but no success yet.

author: flashthunder
author_rank: Contributor
timestamp: March 31, 2024, 03:30:51 pm
content: Success! So, this is what I did to clear the Test 04 error 02 message on bootup. After loading the file provided by Miti my 2245B continued to bootup with Test 04 error 02. I performed the DAC adjustment and completed Cal 08. Then (and due to not having the proper calibration equipment) I decided to just run through the calibrations without making any changes. I started with Cal 01 and after going through each step I hit the Upper Trigger button to store changes, powered the scope down, moved the Cal/No Cal jumper to No Cal...then powered back up and the scope booted to normal mode with no errors and no "?" marks! Yay! I did not go through the remaining Cals as I did with Cal 01. I do know that the scope is not properly calibrated however for my purposes I'm satisfied that coping another "like" scopes calibration data works (as verified by Calibrationfixture). Thanks for everyone's help!

author: Miti
author_rank: Super Contributor
timestamp: April 01, 2024, 01:29:06 am
content: Quote from: flashthunder on March 31, 2024, 03:30:51 pmI don't understand why my file would give you errors, it was read from a working scope with valid calibration. I've validated that file in multiple ways at the time. New Dallas chips, FRAM, and it was always ok. Unless you have a different SW version and the memory map is different, I'm puzzled.But anyways, congrats!Cheers,Miti

author: calibrationfixture
author_rank: Regular Contributor
timestamp: April 01, 2024, 06:45:25 am
content: Hi flashthunder,Also my congratulations. A few years ago I also had to service a 2445B. At Start-Up it has a Test 04 Fail 10 and no Trace on CH2. After some repositioning of the traces (knob-fiddling), Attenuator DC-Cal and some scrolling through the Diagnostics Menu it was gone. Repair successfulCalibrationfixture

author: flashthunder
author_rank: Contributor
timestamp: April 01, 2024, 09:47:02 am
content: Miti, your file did indeed work...it is the file that I am using. I was attempting to point out that I needed to complete a Cal routine before the calibration error cleared. Once I completed Cal 01 steps, and after saving Cal 01 everything worked. I don't understand how the memory section works but it seems to me that once the Cal 01 routine was written and saved then a calibration starting memory location was created. Perhaps that is why the manual states that the cal routines must be completed in sequence (cal 01 followed by cal 02 ect). It worked for me and hopefully this will help others clear those annoying question marks from their screens. Thanks,