Peter Strickland

Mike,
The 744A should have a DS1486 and a DS1650 (or DS1250) NVram on the CPU board.  There is code on the DS1486 that has to be there to boot properly.  Did you copy the old NVram image to it?  I have tons of images from such scopes and can provide one or more if you don't have it.

If by chance you have an older CPU board that has the same watchdog timer as the older TDS500 series, then that code will have to reside on the DS1650 as there is these are not ramified timekeepers.

Also, you did not say if the LED on the CPU board increments from 0 to F and then starts to flash alternating segments (like top/bottom on one side).

Strick

Jesus,
Sorry for late reply, we were on a vacation in Canada.  
My old programmer (a CQ-3 made by MCUmall would refuse to write to the first "D" (hex) and would immediately stop writing the file.  My new CQ-4x4 that I just bought has no problems writing to the chip from the beginning.  
Have you tried just writing the file to the chip?  When you read it after writing, (or if it verifies), it will certainly fail as the first 3 bytes will have changed.  the remaining 11 bytes of the "D" (or 14 decimal) bytes don't change rapidly.

Anyway, if your programmer refuses to write like my old CQ-3, then when you read the file, do an offset of -D and when you write to the chip, do an offset of D.  you need to look at your documentation to see how you do that.  For my CQ-3, when you request to open a file, it asks if you want to off set and when you write, it displays that offset and requests any offset for the write.  Doing a -D read and +D offset will include all the important stuff from the file and the timekeeper will fill in the first D all by itself.

Strick

<p>The 131K (20000 hex) file is for the DS1486 and the 524K (80000) file is for the DS1650.&#160; Quite frankly, I think you could leave the DS1650 blank and it wouldn't matter.&#160; I've seen them with nothing in them and the scope still works.&#160; TEK put the necessary stuff in the earlier part of the memory.&#160; The memory starts at 4000000 and the DS1486 ends at 4020000.&#160; the DS1650 starts at 4080000 and occupies 80000 bytes.</p> <p>When using Tektool, I read and write to both chips with the following:</p> <p>Tektool -r Nvram.bin -b 0x4000000 -l 0xfffff&#160;&#160;&#160;&#160; This covers both chips and works fine.</p> <p></p> <p>Remember, your burner will probably complain about the first 14 bytes (D hex) when flashing the DS1486, as these are owned by Timekeeper.&#160; Also, there is one byte that indicates that the scope is calibrated and you may have to restart to clear or reset it.&#160; Reading and Writing using Tektool avoids this issue and it's handled by the CPU, not a burner.</p> <p>Strick</p>

For some reason, the site will only allow one file... all three zipped below.<br> <br> Strick

<p>Jesus,</p> <p>here is one link from the US:&#160;&#160;<span style="font-size:11pt;"><span style="line-height:115%;"><span style="font-family:Calibri,&quot;sans-serif&quot;;">https://www.ebay.com/itm/153848991230?hash=item23d21d4dfe:g:EvQAAOSw-F1eWjYs&amp;amdata=enc%3AAQAIAAAA4Elfm2%2FlVsmuV2GfmDzBUVYnuIV1RIuWG%2BY0chpldiktcBvvLzDTC5TYe8E%2FxSSHLmmmjVDGzjO6wL8h3b8VA38jQdCL06mwbgWq1Qy074kn1p59cW%2Fm4COQLIWCkGVmJwY%2B%2FlB6odn9BB9Ro7dMFsMO%2Bgf3L%2F2dKXn%2F1xZwTYgtB1hmmlini8pMfI7ksDh0xJY2%2B4gYz%2FxrrK65d2EaCdTXabA8M9O%2BZrRRr8eKucrvfuHIX%2BXSlZ1kYTjoHD7JgGmOhAN2C3lr1Az5l5F1ZbsA7PvqejHi%2BcN9CfOXx%2BgN%7Ctkp%3ABk9SR_a8ppuUYg</span></span></span></p> <p>And another from China:&#160;<span style="font-size:11pt;"><span style="line-height:115%;"><span style="font-family:Calibri,&quot;sans-serif&quot;;">https://www.ebay.com/itm/181266663238?hash=item2a3455c746:g:gx4AAMXQfvlSjtrN&amp;amdata=enc%3AAQAIAAAAwKQk1Xj4AW%2FB3Kk%2FDchkZeR9uL9y3iVzPICfS9NR0TEo%2F3flQ1y7zqudPpwQnMy%2BgAAjytKsqnJBQLGgIqO639Ww2E9sHUa5xxpRg4OkSCBy33VLVET5MvB8wrduvRp5hRQBmKjMxJ1Fq65hQ3wNTmKqSadGVW6ixYf3PyxsYkDvgVcmXT9cN9%2FTjzWO%2FLX4KVGwExBYetWlef4nCk4Ss2yq0zSbaLl77JE3sKsSd02Ktu9if%2BPTlwH%2Bd15e7qEWbA%3D%3D%7Ctkp%3ABk9SR57wyJuUYg</span></span></span></p> <p>I'm attaching the image from the DS1486 and DS1650 alone as well as the combined images of the DS1486 and DS1650 (or DS1250).&#160; The combined image is written with Tektool and avoids the error when writing to the DS1486.&#160; Your rom burner may be different from mine and not care about trying to write to the first &quot;D&quot; bytes.&#160;&#160;</p> <p>The DS1486 file is 131,072 bytes, the DS1650 file is 524,280 bytes and the combined file is 1,048,575.&#160; If you decide to try Tektool, let me know and I'll send the proper parameters.&#160;&#160;</p> <p>I'm also enclosing the DS1486 document.</p> <p>Strick</p> <p></p> <p></p> <p></p> <p></p>

Jesus,<br> You can buy replacement DS1486 chips on greedbay.&#160; Most are clones or refurbished chips from China.&#160; However, some of them seem to work ok.&#160; You can also buy a new manufacture DS1486/DS1650 pair of built up circuits that are available.&#160; Cost is about $100.&#160; Look on the same source.<br> <br> Big deal is that you have to have certain TEK unique information in the first part of the chip that tells the scope about options and other information.&#160; Without it, the scope won't boot fully.&#160;<br> <br> As part of my repair process on these TEK scopes, I record the NVram contents before and after calibration on each scope. Thus, I have several 784A images.&#160; If you want a couple, let me know.<br> <br> To burn to the chip, you can either use a rom burner or Tektool (discussed in length in the old TEK forum) through gpib.&#160; You can also record and reinstall using the floppy system, but I don't currently have a 784A on hand to get the proper image.&#160; Some other reader might.<br> <br> One issue with the rom burner is that you cannot write to the first &quot;D&quot; bytes of the DS1486 chip and there is a test byte that will probably fail your calibration on first startup.&#160; cycling or rerunning the POST should clear it as the calibration is stored on the ACQ board, not the CPU board.<br> <br> Strick