|Schematic: ||RE, MF|| ||
|Max. Rate: ||30 MHz|
An early entry into the lower end of the counter market, as inexpensive ICs became available.
Based on standard 7400 TTL - 7490, 7475, 7441 counter string.
Very simple from the user interface side (frequency only) but note the reasonably
high count rate compared to far more expensive counters from just a few years earlier.
- Unit Log -
|Serial Number: ||03313|
|Year of Manufacture: ||1972 (IC date codes of 72xx).|
|Date of Receipt: ||Apr 1997|
|State upon Receipt: ||Input triggerring seems a little erratic.|
Some reorganisation of wiring and cleanup of PCB.|
|Date: ||28 Apr 2008|
|Procedure: ||Power cord replaced with IEC socket.|
- Unit Log -
|Serial Number: ||(not specified)|
|Year of Manufacture: ||1973 (IC date codes of 7140-7307).|
|Date of Receipt: ||Aug 2011|
|State upon Receipt: ||4 of 5 NIXIEs gone, faceplate cracked, case-top screws missing.|
|Date: ||Aug 2011|
|Procedure: ||With NIXIEs installed, display lights up but is unresponsive.
Input sensitivity COARSE control adjusted till responsive.
Unit now counts, but displays a number 2 or 3 times the proper frequency, i.e. 1KHZ displays as 3KHz.
Output from U25 (74H102, Heath 443-43) mimics clock input rather than being divided by 2.
Replaced with 7472 (lower speed).
Input sensitivity also needs to be properly adjusted to minimum needed, otherwise multiple counting may occur.
LSB still flaky, not displaying all numerals.
Board removed and examined. PCB traces between LSD driver and NIXIE are a mess, several had been replaced with wires.
Earlier repairs removed, socket removed, area cleaned, traces replaced with wires.
Case-top screws replaced.