Well, that is a promising start, you can never be sure of what you are going to find when the seller does not show photos of them powered. So far you have an excellent score there, well worth the trip to collect them. N%*&s are sought after in meters these days.
Probably a promising finish too. I can't even find the weston standard cell in the schematics!
I haven't found a manual for the True RMS AC Unit, and I'm not sure I can be bothered to randomly twiddle pots without knowing what they do.
I've already flipped one n%*&e DVM and I'll probably flip these, leaving me only a Fluke 8300A
The Weston cell in the 1619 & 1620 is a tiny thing, in the 1619 it's hidden under a small cover behind the range switch, almost could be confused with a fuse, but it isn't one. And yes it's dead too.
If you want to flip the 1420 DVM, then I would be very interested, I have to say they both look in much nicer condition then what I've found locally.
I'll keep that in mind; what's your particular interest?
The inside is a bit messy, as you would expect with a grille top panel.
From the attached PDF, it seems it is actually an LM1420.2BA
To join my Solartron DVM collection, would be nice to have the extra AC option too, also need an input cable to test & repair the standard LM1420s I have, still need to locate a two terminal input cable for the LM1440, or convert it to the later three terminal connector used on the 1420.
Forgot to mention the 1420 has a counter mode, but frequency range is quite limited.
Some extra catalog data, must be older than the pdf you have, as there is no mention of the ohms addon. The paper LM1420 manual I have only covers the standard model, no options.
David
My pdf is marked "received 2 feb 1966". A quick AC frequency test made me think of the ~20kHz and ~100kHz figures. I saw the counter option, and it looks remarkably awkward to use. The whole thing runs from a 500kc/s oscillator.
My cable is in not wonderful condition by the plug, and has the worst 4mm banana plugs I've ever used. Neither is a real problem, of course.
I looked closer at the schematic and found the Weston cell where it ought to be, but marked as X1 not the expected B1. I delved into the instrument's entrails, and found the weston cell near the range switch, but fully encased in black plastic. I was able to measure the voltage, a remarkable 1.018725V at 25C. According to
Conrad Hoffmann, the voltage should be 1.0190V @ 20C, decreasing by 5µV/C as the temperature rises, so if new my cell should be 1.018975V. Cells tend to decrease voltage by 25µV/year (with quite a wide range), so my 250µV fall equates to 10years. Not bad for something that is at least 50yo with a life expectancy of 7-14years, with 1.0183V being the endpoint!
The pictures below show a general view including internal dust, the rather strange back panel, and two of the Weston cell, DC range, and AC electronics. The yellow Wima caps next to the Weston cell are the switchable input RC filter, 3dB at 11Hz.
In deference to Vince, I'll leave you to expand them.
EDIT: added the last photo, showing details of the condition of some digital and display boards. All digital circuits circuits are classic 2 transistor 2 diode 6 resistor 4 capacitor multivibrators, or similar.