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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.
523-002032 | |
1970 (PCB edge connector labeled 70.6.01) | |
Correspondance with Jef Ongena / 2023 Aug. | |
Physical repairs by J.O. | |
Non-functional, several non-sensical patches and apparent repair attempts in unit. | |
Functional (2023 Sep). |
2023 Sep | |
Display is filled with either 0s or 9s and multiple decimal points. | |
Patches and alterations had been made which logically make no sense.
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Undoing these restores most functionality. Subtraction and division still have faults. |
2023 Sep | |
Subtraction producing a negative result does not set the negative-sign indicator on, although the numeric result is correctly presented. | |
SNO not being set. TN1 has CE short. | |
TN1 replaced with BC556. |
2023 Sep | |
Division hangs. | |
State machine stuck in state 32. FDAT not being asserted to terminate loop. RY not being shifted up. | |
UB3.14 input faulty. Passive 2-input NORN gate constructed at pin 12 to create input to substitute for pin 14. |
523-002750 | |
1970 ~ | |
Correspondance with Jef Ongena / 2023 Sep. | |
Physical repairs by J.O. for S. | |
Non-functional. | |
Functional (2023 Sep). |
2023 Sep | |
Master clock ΦC absent. 2SA611 driver transistor faulty. | |
Transistor replaced with BC312. Some confusion over lead order, installed as EBC. |
2023 Sep | |
Master clock ΦC LOW period is quite short, ~ 7 µS. Results in ΦEOD and ΦEON in or near violation of IC clocking specs. | |
LOW period lengthened by paralleling pulser 330pF capacitor with 200pF. |
2023 Sep | |
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. | |
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. | |
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 |