Back in 1992 I bought two copies of the desktop electronic clock "Electronics 2-08". They are made on chips CIE, CIE, on KIZ the scheme, similar to that set out in article V. Bannikova "Electronic watch from radiokonstruktor Effect-4" ("Radio", 1993, No. 10, pp. 28-31, Fig. 3).
In both hours, the brightness of the indicator IVL-7/5 gradually decreased and just one year later the numbers were barely visible. The indicators had to be replaced and repeat this operation for the past 10 years four times.
Did not give a positive result and replacement (taking into account differences in the Pinout and filament voltage) indicator IVL 1-7/5 on the MD-4 is the same as in hours "Electronics 6.03" on the chip KAHL where the indicator works without replacement for nine years. Smoothly, and almost retaining the original brightness, serves as an indicator IVL 1-7/5 hours in a makeshift collected many years ago on the above-mentioned scheme V. Bannikov.
All this led to the idea to explore the "strange" watch and find the cause of damage indicators. The audit showed that all the supply voltage is normal, however the pulses at the outputs of the code Converter KIZ have a complex three-tier form, which does not happen in hours according to scheme V. Bannikov. During the inspection of the factory the PCB has detected that there are no specified hours in homemade the resistors connecting the terminals 9-15 chip CIJ with power source negative polarity. No holes and pads for them installation.
The missing resistors (R1 - R7) were mounted in hinged manner on the scheme, shown in the figure. Here C1 is available in hours filter capacitor rectifier. The voltage values indicated are relative to the common wire, which in hours connected conclusions 8 Converter code KIZ and other circuits.
After modification of the pulse shape on the findings of the Converter and connected indicator IVL 1-7/5 was the same as in self-made watches. About life the indicator placed instead of the lost brightness, too early to judge, but for since that time common to all indicators to Refine a gradual decrease in brightness is observed.
As far as the author knows, unjustified "saving" a few resistors, leading to premature deterioration of the indicator, is not only found in "Electronics 2-08", but in a similar scheme table electronic clock, released under other brand names.
Installing the resistors in question, provided standard scheme enable code Converter CIJ, the outputs of which (unlike outputs similar in structure CID) is made with "open" drain. It is strange that factory hours it was previously neglected.
Author: A. Butov, S. CORBA Yaroslavl region