Doug and all,
I just acquired one such unit (HP8904A), and indeed, it is exceptionally accurate. Its 10MHz internal reference measures at 4.1ppm off on my oven conditioned HP5328A, and the DC levels are almost as accurate as I can measure them with my Fluke 8840a (for instance, the 10V DC level reads at 10.0003V). AC amplitude levels read with my HP54522A are at 0.00000V off for the 0.1 and 1000Hz signal. Wherever I am seeing deviations, they are usually an order of magnitude less than the allowed tolerance.?
Anyway, VERY impressed. This is a unit which, as far as I could put it together, was in a maintained lab until some part of 2020, but since has been on eBay at least twice. Funny thing is it's been last looked at by a metrology lab in my literal neighborhood, then spent these 1-2 years somewhere in AZ, then came back to the neighborhood in CA to join my herd.?
Now, on to the issue at hand - I'm very interested in replacing the LCD with a hopefully far more legible unit. Can anyone indicate some clear directions, if available anywhere, and maybe LCD units to use for this? I've seen Doug's recommendation, but I'm a bit weary the shield doesn't seem to fit behind it. The other concern is with the 80V source for the old unit that seems to need a load of sorts to be happy.
Radu.?
