Re: 8753C VNA option upgrade
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Hello Group, I un-soldered the EEPROM from my HP8753C and went in and modified the necessary bits and I was able to enable options, 002, 006, and 010. I soldered in a IC socket and copied the original EEPROM contents to a new IC, (obtained off of Ebay), and used my programmer to copy its contents and it works fine. I also have a HP85047A and it works well with the VNA, now with options enabled. There are articles on the Internet describing what bits to modify to enable these options.
On Sunday, February 23, 2025 at 06:14:12 PM MST, Jinxie via groups.io <paul666@...> wrote:
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Here’s the deal: HP (and later Agilent) locked these options behind firmware codes tied to the instrument’s serial number. Back in the day, you’d buy the upgrade, call up HP with your serial, and they’d send you a unique key to punch in via the front panel or HP-IB interface. The process involves accessing the service menu, tweaking some settings, and entering a code that rewrites the EEPROM to flip the option on. Without that official code, it’s a bit of a gray area—legally and technically.
Now, I can’t hand you specific codes myself—those are proprietary and unique to each unit’s serial number. What I can tell you is how it’s supposed to work based on what’s out there. On the 8753E, you’d typically:
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Power it on, hit Preset, then dive into the Service Menu (usually something like System > Service Menu, though exact key combos depend on firmware—check the manual for your revision).
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Find the option enable function—might be labeled “Enter Option Key” or similar.
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Input a code, which is often a string of numbers or letters HP would generate.
The catch? Getting those codes today. HP/Agilent/Keysight don’t exactly advertise them anymore, and support for the 8753E has long tapered off. Some folks in the test equipment community—like on forums such as EEVblog or the old HP/Agilent groups—claim you can email a guy named “Caesar” (caesarv@...) with your serial number and desired options. He’s rumored to reply with codes that work, no hardware mods needed for software options like 002 or 010. For 006, though, you’re likely stuck unless your unit already has the 6 GHz source hardware—unlocking it without the right guts won’t magically extend the range.
Problem is, that email’s been floating around since at least the early 2000s, and there’s no guarantee it’s still active in 2025—or that it’s legit. Plus, messing with the EEPROM carries a tiny risk of bricking the thing if you fat-finger it. You’d need to move a jumper on the CPU board to enable writes (documented in the service manual), enter the code, and pray.
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That's about as much as I know on the subject but I'm sure there are others on this group who will further assist.
Good luck!
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