| Manufacturer: | Weston |
| Model: | 1240 |
| Year: | 1972 |
| Schematic: | (see comment) |
| |
| Functions: | DCV, DCmA, Ohms, ACV, ACmA |
| Display: | NIXIE |
| Digits: | 3.5 |
| Logic: | RTL, Fairchild CµL |
|
Benchtop DMM from Weston.
This unit was manufactured in 1972, however the model is likely from around 1969-70.
The model has auto-polarity but not auto-ranging.
Fairchild CµL (Counter Micrologic) is used for the counter string.
CµL was a small series of RTL-class MSI devices introduced by Fairchild in the mid-1960s intended specifically for decade counter-displays.
The series is comprised of 4 IC types:
- the 958 decade counter,
- the 959 4-bit latch,
- the 960 decimal decoder / NIXIE driver,
- the 989 4-bit modulo-16 counter.
The Heathkit IM-102 uses an essentially identical circuit design,
the IM-102 appears to have been a copy of this Weston model.
Internal view.
- Unit Log -
| Serial Number: | 89463 |
| Year of Manufacture: | 1972 (Component date stamps of 7104 to 7215). |
| Date of Receipt: | 2013 Oct |
| State upon Receipt: | OK physically, ohms not functional, NEG lamp flaky, POS lamp dim.
Black plastic over metal handle fracturing. |
| Date: | 2014 Jan |
| Procedure: | Cleaned. Grease replaced on rotary switch, not replaced on pushbuttons. |
| Date: | 2014 Jan |
| Symptoms: | On all ohms ranges, overrange does not light, any R takes display to 0. |
| Procedure: | Fuse in V/Ohms connector blown. Fuse was 3/16A, replaced with spare 3A located in COM connector due to lack of fuses of appropriate size.
All fuses in model are uncommon AGX size, shorter than the standard AGC. |
| Date: | 2014 Jan |
| Procedure: | POS and NEG lamps replaced. Originals were stubby neons (~1/4" long), replaced with more common type (~3/8"). |
