Privileg 861 MD

Date of introduction:  1976 Display technology:  Fluorescent
New price:   Display size:  8
Size:  5.4" x 3.3" x 0.8"
 138 x 85 x 21 mm3
Weight:  4.8 ounces, 135 grams Serial No:  76987
Batteries:  2*AA Date of manufacture:  mth 04 year 1976
AC-Adapter:   Origin of manufacture:  Far East
Precision:  8 Integrated circuits:  TMS1071 (KAΔ7611)
Memories:  1 Displays:  ISE DP89A
Program steps:   Courtesy of:  Joerg Woerner

Quelle AG was - together with its arch rival Neckermann - one of the leading department stores in Germany and distributed most of their electronic products under the "privileg" label. This Privileg 861 MD calculator caught our attention in 2023 while researching Texas Instruments' TMS1070 Product family of "single-chip calculator circuits" and noticing the [+/−] key missing on the keyboard of the related TI-2550 II. But a much bigger surprise was the ancient Vacuum Fluorescent Display (VFD) used with the featured calculator.

Dismantling this Privileg 861 MD calculator manufactured in April 1976 by an unknown OEM (Original Equipment Manufacturer) in Far East reveals a very cost effective design using a single-sided printed circuit board (PCB) centered around a TMS1071 single-chip calculator circuit connected to a 9-digit VFD, a keyboard assembly and powered by 2 AA-sized alkaline batteries.

The TMS1071 is a member of the TMS1000 Microcomputer family introduced in October 1974 with the SR-16 calculator. While the TMS1000 design was mainly intended for designs using power-hungry LED displays with external display drivers, uses the TMS1070 redesigned output drivers for the 11 R-Outputs (Display Scan) and 8 O-Outputs (Segments) that can withstand voltages up to -35 Volts and hence allows direct operation of low-voltage VFDs.

The Privileg 861 MD makes fully use of the TMS1070 design and we could identify on the PCB both the voltage converter to generate a -30 Volts supply for the Ise Electronic (ISE) DP89A display and the external "pull down" resistors for the R- and O-Outputs. ISE invented VFDs in 1967, selling most of their displays under the Noritake brand. The DP89A with its unique bathtub-style glass construction and two 14-pin connectors is one of the first multi-digit VFDs ever made and branded with the rarer ISE logo.

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Joerg Woerner, February 13, 2023. No reprints without written permission.