Early
Electronic
Calculator		 TEAL IME 41 Calculator

Manufacturer: TEAL
Model: IME 41
OEM: TEAL
Year: 1970
Form: Desktop
Functions: Basic four, Accumulate
Number of Digits: 12
Display Type: VFI
Display:FUTABA DG12C
Logic Technology: DIS,SSI,MSI
Memory Technology: MSI-MOS
Diodes: 458 =256+42*4+7*4+6
Transistors: 34 =4+1+12+3+10+2+2
Principal ICs: JMOS
IC Complement:NEC µPD112C (1), Hitachi HD3107 (5), Mitsubishi M5811 (3), Mitsubishi M5812 (2), Mitsubishi M58201 (2), Mitsubishi M58204 (1), Mitsubishi M58206 (5), Mitsubishi M58212 (11), Mitsubishi M58214 (1), Mitsubishi M5825 (3)
(34 total)
Tech. Data Level: 3
Tech. Data Source: RE
Tech. Data Pages: 18
Tech. Data:Schematic (pdf)

Another basic four-function-with-accumulator OEM'd by TEAL, here for the Italian IME. The electronics & logic design of this model and the TEAL Riccar are essentially identical. The main differences between them are the display - vacuum-flourescent for the IME-41 versus Nixie for the Riccar, and the IME having additional features of 5/4 rounding and a double-zero key.

The calcuseum site shows the apparently same OEM model badged as the Busicom 121-DB and as an NCR model.


Internal view.
Main logic board with registers and state machine. This appears to be an earlier version of the board. A later version has alterations making the circuitry closer to that of the Riccar.
Display board, with timing and keyboard logic.

- Unit Log -

Serial Number: 523-002032
Year of Manufacture: 1970 (PCB edge connector labeled 70.6.01)
Date of Receipt: Correspondance with Jef Ongena / 2023 Aug.
Source: Physical repairs by J.O.
State upon Receipt: Non-functional, several non-sensical patches and apparent repair attempts in unit.
Current State: Functional (2023 Sep).

Date: 2023 Sep
Symptoms: Display is filled with either 0s or 9s and multiple decimal points.
Analysis: Patches and alterations had been made which logically make no sense.
  • ST11~ connected to NO12SINCE11~ around DA20 & DA21.
  • NO12SINCE11~ connection to ST19~ opened.
  • K00INJ~ replacing STRYLA~ into BCD-correction circuitry.
  • DA1 installed backwards.
Solution: Undoing these restores most functionality. Subtraction and division still have faults.

Date: 2023 Sep
Symptoms: Subtraction producing a negative result does not set the negative-sign indicator on, although the numeric result is correctly presented.
Analysis: SNO not being set. TN1 has CE short.
Solution: TN1 replaced with BC556.

Date: 2023 Sep
Symptoms: Division hangs.
Analysis: State machine stuck in state 32. FDAT not being asserted to terminate loop. RY not being shifted up.
Solution: UB3.14 input faulty. Passive 2-input NORN gate constructed at pin 12 to create input to substitute for pin 14.

- Unit Log -

Serial Number: 523-002750
Year of Manufacture: 1970 ~
Date of Receipt: Correspondance with Jef Ongena / 2023 Sep.
Source: Physical repairs by J.O. for S.
State upon Receipt: Non-functional.
Current State: Functional (2023 Sep).

Date: 2023 Sep
Symptoms: Master clock ΦC absent. 2SA611 driver transistor faulty.
Solution: Transistor replaced with BC312. Some confusion over lead order, installed as EBC.

Date: 2023 Sep
Symptoms: Master clock ΦC LOW period is quite short, ~ 7 µS. Results in ΦEOD and ΦEON in or near violation of IC clocking specs.
Solution: LOW period lengthened by paralleling pulser 330pF capacitor with 200pF.

Date: 2023 Sep
Symptoms: Display varies at power-up, some digits may be off, may be multiple decimal points on, zero-blanking ineffective. Pressing a numeric key changes the display to a single 0 in LSD. LSD 0 excessively bright when "00" key pressed.
Analysis: ST11 not being asserted. ST12, 35, 34 overlap for numeric key presses. Hypothesize overlap is a result of NO12SINCE11 remaining asserted. If inverter UP2.11-12 has short(s) to GND, could explain both overlap and ST11 absence as ST11~ would be pulled HIGH through diode DP27. Inverter UP2.11-12 found to be faulty.
Solution: For testing, unused inverter in IC on main board wired in to substitute for UP2.11-12. In final, to avoid extra wires between boards, simple inverter constructed from bipolar to replace UP2.11-12.


  TEAL IME 41
Calculators | Integrated Circuits | Displays | Simulations
EEC 		bhilpert