Products > Test Equipment
Agilent 34401A VFD replacement
Veteran68:
2-3 years back I purchased a very good condition 34401A from a fellow eevBlog Forum member, and it's been a great meter for my hobby use. I have over a dozen handheld meters ranging from a Fluke 87V and Dave's BM786 on the higher end to Aneng and Voltcraft meters on the low end, but I always wanted a quality high-digit bench meter and this 34401A fit the bill nicely.
While we were in between houses, I had it packed up and in (climate controlled) storage for nearly a year. After getting the basement of my new house remodeled into an office/lab/makerspace I got it setup but hadn't used it for some time. Recently I've been working on a laptop repair and noticed that the VFD is flaky in places. Some spurious extra segments are appearing and disappearing at random. See photo I just took showing the extra segment on the "V" making it look like a "K". They've also come and gone from different areas of the display. Sometimes, I think after it's been powered up for a long time and warmed up, they disappear and everything looks normal.
Is this as simple a repair as picking up a $50 VFD off of eBay? Or is there more to it? I've seen comments online that indicate old vs new models have different video driver boards that aren't compatible. Does this look like a driver board issue vs just a VFD issue? Looking for input from anyone who has seen a similar issue and undergone a repair.
Thanks!
David
daisizhou:
Compatible displays are made of LED,It is recommended that you first disassemble the host for inspection before determining the maintenance plan
JenniferG:
I ran across the following mod for this meter. It replaces the VFD with OLED display. Uses an STM32 microcontroller. THe HP uses SPI for the display I read in the article. He shares the kicad files, gerbers and firmware source.
https://hackaday.com/2018/08/29/faded-beauty-dmm-gets-an-oled-makeover/
I have no clue how good the mod is.
Hydron:
If you're lucky it's just the VFD driver (scope it to check I guess), and you'll be able to get one off ebay or something. Schematics are available in the service manual.
IIRC the units with black LO connectors use the newer display design with separate driver and micro-controller, so you've avoided the ones with an un-repairable display. The VFD itself looks nice and bright (better than mine at least!).
HighVoltage:
The original front panel PCB with VFD is still available from Keysight.
Navigation
[0] Message Index
[#] Next page
Go to full version