| Manufacturer: | Fluke |
| Model: | 1900A |
| Year: | 1976 |
| Schematic: | MF |
| |
| Max. Rate: | 80 MHz |
| Display: | LED |
| Digits: | 6 |
| Logic: | TTL, CMOS, MSI |
|
Counter with Auto-ranging feature.
Internal view.
Units with the battery option require NiCd batteries to be present for operation.
Shown here is a unit modified with a simple shunt regulator to substitute for the batteries.
The transformer used with the battery option does not supply sufficient overhead voltage to
allow use of a standard series-pass regulator.
See battery substitute schematic.
Also in the above unit, the power connector had shorted and blown a hole in the PCB.
A standard IEC power connector has been installed in its place.
- Unit Log -
| Serial Number: | 2328047 |
| Year of Manufacture: | 1979 (IC date codes of 7903-7945). |
| Date of Receipt: | 2012 Oct |
| State upon Receipt: | Functional. Line power version (no batteries). |
- Unit Log -
| Serial Number: | 1263-C |
| Year of Manufacture: | 1976 (IC date codes of 7248-7629, mostly 1974). |
| Date of Receipt: | 2012 Oct (customer repair) |
| State upon Receipt: | Counts in Total mode but does not update in Frequency mode (no gate or sample cycle).
Power receptacle had previously shorted out, burning large hole in PCB.
This unit has the battery option. |
| Date: | 2012 Oct |
| Procedure: | Sampling problem traced to bad U5 4011 IC, some gates (1-2-3, 4-5-6) are 'weak'/inadequate gain.
U5 replaced. Functional. |
| Date: | 2012 Oct |
| Procedure: | Modified for use without batteries by substituting a shunt regulator for the batteries. |
| Date: | 2012 Oct |
| Procedure: | IEC socket installed to replace original receptacle. |
| Date: | 2012 Oct |
| Procedure: | Overflow LED not lighting.
Works after resoldering. |
