Uploaded February 2024 | Updated September 2026, 1 week ago
In this video, I describe the Weston/Schlumberger model 1240 digital multimeter, a very influential, high quality design from 1969. Amongst other things, it's circuit design and specifications were adapted by Heathkit for their first digital multimeter, the IM-102.
The video includes an introduction to the meter, details on how to disassemble and reassemble the meter for maintenance, my restoration process, tour of the printed circuit boards, a demonstration, a look at the 1240's original manual, and a detailed talk on the circuit theory as I take the viewer through the schematic diagram
Because of the difficulty in obtaining documentation for this meter, I have created detailed and fully vetted new CAD-drawn documentation, including a three page schematic diagram (analog, logic, power), tables of semiconductor part substitutes, simple calibration procedure, abbreviated circuit theory, and many other details useful to anyone trying to restore and use the 1240. This document may be downloaded from:
serpentwebsite.com/fileshare.htm
Timetable of video contents:
00:00 Introduction & history
04:35 Disassembly
17:53 Tour of printed circuit boards
38:30 Restoration
42:23 Reassembly
44:56 Demonstration
53:21 Beauty shot
53:57 Manual
1:10:34 Schematic diagram & circuit theory
2:27:45 Plans for fabricating a new handle/stand
In this video, I describe the Weston/Schlumberger model 1240 digital multimeter, a very influential, high quality design from 1969. Amongst other things, it's circuit design and specifications were adapted by Heathkit for their first digital multimeter, the IM-102.
The video includes an introduction to the meter, details on how to disassemble and reassemble the meter for maintenance, my restoration process, tour of the printed circuit boards, a demonstration, a look at the 1240's original manual, and a detailed talk on the circuit theory as I take the viewer through the schematic diagram
Because of the difficulty in obtaining documentation for this meter, I have created detailed and fully vetted new CAD-drawn documentation, including a three page schematic diagram (analog, logic, power), tables of semiconductor part substitutes, simple calibration procedure, abbreviated circuit theory, and many other details useful to anyone trying to restore and use the 1240. This document may be downloaded from:
serpentwebsite.com/fileshare.htm
Timetable of video contents:
00:00 Introduction & history
04:35 Disassembly
17:53 Tour of printed circuit boards
38:30 Restoration
42:23 Reassembly
44:56 Demonstration
53:21 Beauty shot
53:57 Manual
1:10:34 Schematic diagram & circuit theory
2:27:45 Plans for fabricating a new handle/stand
