Products > Test Equipment
Upgrading the HP/Agilent 8714C from green CRT to color LCD
TheSteve:
--- Quote from: Hero999 on December 27, 2015, 05:04:55 pm ---Here's a constant current LED circuit which should do the job.
--- End quote ---
Thanks for the schematic. I was pondering using a single supply opamp driving a pass transistor last night which would have been easy to make vary the voltage from 8 to 12 volts going into the existing 20 ohm resistor. I thought I would bread board your schematic though and it worked fine so I went with it. The BC237 was swapped for a 2N3906 and the two BC337's were replaced with a single TIP31C and a small heatsink I ripped off an old eprom programmer. I used the 4.7K resistor during testing but after installing it I wanted a little more drive current so I paralleled a 5.1K with it. This gives me adjustable drive current from 40 to 220 mAh. The new board is mounted in the original metal box I added, everything is working great. There was a small delay during final assembly when some hardware went missing. It was in a small plastic film container. It seems "Hunky Bill" thought it made a great toy as it rattled quite nicely when batted around. Attached are pics of the driver board, one showing it installed in the metal box, a shot of the LCD with the front panel removed and a picture of Hunky Bill in his "rest state" after taking a round out of any and all equipment in the shop.
I think it is finally time to stop taking the 8714C apart and put it to work!
AF6LJ:
That's really great, looks good.
andy2000:
I just picked up an 8711C which I've turned it into an 8712C with all the software options. I found that writing 00 for the four option bytes turned it into an 8730A tuner analyzer. I had to use 8B as found on this page:
https://translate.google.com/translate?hl=en&sl=cs&u=http://minolta1.cninet.cz/HP8712C/&prev=search
Next I'm going to try to use the digital LCD interface. It looks like a standard 4 bit parallel output which should work with many LCDs. The LCD gets its data from the same source as the DAC for the VGA output, so assuming there's no issue with timing, I think it should work.
Keysight was nice enough to post schematics for the 871XC:
http://na.support.keysight.com/871x/schematics/
andy2000:
I finally go around to adding the digital LCD interface. It all went smoothly and worked the first time. I just need to remove the CRT and mount the LCD. I used a Mitsubishi AA084VC03 LCD panel. I'll post some more detailed pictures soon.
R005T3r:
Nice upgrade! :-+ :-+
I'm very interested in these mods, maybe I can try to upgrade my old HP5402A with an LCD panel. The thing is, if something goes wrong I don't have any other scope...
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