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Upgrading the HP/Agilent 8714C from green CRT to color LCD

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rfdes:
I see that this original post is from several years ago but wanted to reach out and see if anyone would be interested in a software patch for a timing issue that I discovered while modifying my HP87xC unit to accommodate an LCD display.

I took the approach of populating the CPU assembly with the LCD display components and using a raw LCD panel (NEC NL6448BC26-03). All went without a hitch and I was very happy with the outcome(almost).  However, I discovered that the default horizontal/vertical timing for 640x480 60Hz was not as accurate as needed  for an LCD panel.  The default timing would leave a white line on the left and top of the screen.  Using the 'CRT adj' controls would not allow precise enough adjustment for an LCD screen.  For an analog CRT it works fine.   The first two pics show the issue that I am describing, i.e. I had no way of accurately centering the image.  I tried using the analyzer's CRT manual entry timing parameters with no luck.  Now most people would say: 'Why bother?' but I could not leave good enough alone and decided to reset the default H & V timing to the proper values.  I reverse engineered the UNIX firmware and created an new version of the C.04.52 firmware that fixes the issue. See Pic 3.  If anyone is interested in my version of the main firmware, send me a PM and I will email you a copy.  I also have patched the Boot Rom to also fix the timing problem during boot.  You're welcome to a copy of my Boot patch also.
Thanks
Jim

TheSteve:
I don't have my 8714 anymore but you did some great work, I really appreciate you sharing it with others.

rfdes:
I've owned my analyzer for about 10 years but only recently did I decide to upgrade the LCD screen after reading your original post.  When I first got my unit I had spent some time designing a key-gen for enabling the different options (enjoyed the challenge).  Unfortunately, the Key-Gen option algorithm will not work for enabling the full Vector capability.  You still needed to patch the boot ROM.  I had planned at the time to reverse engr and patch the main firmware so that the user would only need to perform a firmware install in order to enable ALL options plus vector capability. 

Well, while I was working on the timing issue patch, I went ahead and created a modified firmware to force all options+vector.  I guess I should go back and patch the 'A' and 'B' versions as well and then submit them to the HP-Agilent-Keysight-equipment@groups.io.  Not sure anyone would care to use this method, but the hope was that this would eliminate the need to yank out the CPU assembly and reprogram the boot ROM.  Many people don't have access to a device programmer.

Take care -
Jim

VSS:
Hello

I have purchased an HP8712 and want to replace the CRT screen.
I have read your description and I have a few questions:
1. Can you describe exactly to which pins you connected the RGB signals from the VGA port? I don't see it in the picture.
2. Where is the synch H and synch V signal and power +12V on the tape?
3. How do I remove the picture tube? Do you need to disassemble the coils on the tube?

Thank you for your response
Artur SP3VSS

VSS:
Hi all

My HP8712 has a new display: D
LCD panel bought on Aliexpress: https://www.aliexpress.com/item/4000328921850.html
Display and driver holder designed in Fusion360 and printed on the Ender3.
Files at https://www.thingiverse.com/vss/designs
Controlling the display by a remote control and an infrared receiver.

Thank you for your inspiration!

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