Digital Test
Para-Time Instruments Inc. 130

Manufacturer: Para-Time Instruments Inc.
Model: 130
Year: 1967
Schematic: RE
Max. Rate: > 90 KHz (measured)
Display: dekatron
Digits: 4
Logic: tube, transistor, RTL

A nice little dekatron-based counter.

This model is notable for it's combination of old and new technologies. The counters/display are dekatron tubes. Dual-triode tubes are used for the inter-digit dekatron drivers. RTL integrated circuits make up the timebase and control logic, and a few discrete transistors interface between the RTL and the tubes.

Two types of dekatron counter tubes are used. The first two digits (LSD) use high-speed type 6909 dekatrons, while the remaining digits use 6802 dekatrons. The 6802's have the orange glow typical of neon while the 6909's have a purplish-pink glow. Other than that, their physical appearance and internal construction appear identical. A tube manual indicates the 6802's are good to 5KHz while 6909's should count up to 100KHz. This unit seems to count reliably to over 90KHz.


- Unit Log -

Serial Number: 0012
Year of Manufacture: 1967 (Capacitors stamped with 6621, 6708).
Date of Receipt: 1997 Jun
State upon Receipt: Non-functional. Fair physical condition.

Date: 1997 Jun 30
Procedure: 2N3877 for reset replaced.

Date: 1997 Jun 30
Procedure: Neon bulb in gate lamp bad. Housing opened and terminal strip installed to provide contacts for replacement bulb.

Date: 1997 Jun 30
Procedure: Input circuit rewired.

Date: 1997 Jul 03
Procedure: One 6909 dekatron not functional, modifications to bypass the 1st digit (LSD).

Date: 2003 Nov 28
Procedure: Fuse blown (1A), two 1N4002 diodes in logic power supply (ground side) shorted, all 4 replaced.

Date: 2011 Jul 04
Procedure: Three 6802 tubes and one 6909 received from defunct Coulter Counter from 1963. Bypass circuitry undone and 6909 placed in 1st digit. Unit counts to over 90KHz.

  .. | Para-Time Instruments Inc. 130 | ..
Early Digital Test Equipment