How to replace an imported microcircuit in a telephone set. Encyclopedia of radio electronics and electrical engineering

Encyclopedia of radio electronics and electrical engineering / Telephony

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Materials about imported telephones have been published more than once in "Radio Amateur" both in the past and this year. The most serious publication on the repair of imported TA was published in No. 10/92 under the heading "KR1008VZH1 - in an imported telephone." Unfortunately, the editors did not have a choice of materials on this topic at that time, and they really wanted to help the numerous owners of faulty devices, and therefore this article without the author's signature, in the "market" version, was published.

Today, the editors have more complete material on the repair of imported phones, and the previously unknown author of the "market" material kindly provided "RL" with a more detailed description of the repair methodology, sent amendments to some inaccuracies of the previous publication, and also developed a drawing of an additional printed circuit board with transitional contacts for self-replacement foreign dialers to the domestic chip type KR1008VZH1.

The difficulty of replacing imported integrated dialers lies only in the fact that the pinout of the KR 1008VZh 1 microcircuit does not match any of the foreign microcircuits. However, there is always room in the phone case for a small adapter board, which can, for example, be placed between the telephone capsule and the main board, as shown in Fig. one.

Ris.1

The design of the adapter board and its scheme printed wiring shown in Fig.2, and the circuit diagram - in Fig.3. The board contains a KR1008VZh1 chip and key transistors with correction and protection elements, as well as 1 2 contact pads, to which an adapter harness of thin wires is soldered. Abbreviations indicated on the diagram: IR-pulse key (output to dialing), OTB - hang up, P - switch, + Ep - positive power wire.

Ris.3

The connection diagrams of the pads of the adapter board with the pads of the main board, from which the faulty dialer chip was soldered, are given in Table 1.

Table 1

For example, pad 4 on the adapter board (next to pin 22 of the KR1008VZh1 chip) must be connected to the pad from pin 16 of the KS5805A chip on the main board. Similarly, this contact is connected to the place from the desoldering of pins 14, 1, 18 of the WE9192B, UM9151-3, UM9151 microcircuits, respectively.

In order for the last dialed number redial to work on the phone, changes must be made to the dialing board. On this board, you need to break the track that leads from pad 7 to the "#" button, and solder the broken end of the track from this button to pad 3. The diagram of changes in the connections of the board's typesetting field with contact pads is shown in Fig. 4.

Figure 4

If all connections are made correctly, and the number is not dialed, then the cause may be a low voltage on the zener diode of the riser (less than 1,5V). In this case, it is necessary to increase the current through the zener diode by reducing the resistance of the resistor R1 to 2,2 ... 10 kOhm. (Fig.5). In rare cases (if the handset is off and there is no beep), it is necessary to add a resistor R2 with a resistance of 100 - 300 kOhm.

Ris.5

The pinout of foreign transistors used in handsets and their domestic counterparts are shown in Table 2.

Table 2

Author: A.Kizlyuk, Moscow; Publication: N. Bolshakov, rf.atnn.ru

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