Products > Test Equipment
Tektronix 2445B calibration
(1/3) > >>
flashthunder:
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!

 
MarkL:
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/#msg4750262

It 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!
flashthunder:
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,
Miti:
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.
flashthunder:
Miti, thanks...I would love to compare your file with the one I currently have.
Navigation
Message Index
Next page
There was an error while thanking
Thanking...

Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod