Repair of IVP Sega Mega Drive-2. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Телевидение
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We are talking about video game consoles (IVP) of the second generation, made on the basis of two LSI in QNP packages (97xx, 98xx with 160 and TA-06W, TA-06S - with 128 pins). In addition to them, the IVP board contains two HM53461ZP-12 video memory RAM chips and an R, G, B signal converter into a full video signal of the PAL KA2197D or СХА1145Р standard (the AUDIO signal passes through the same chip). As in other IVPs, an integral stabilizer 7805 is used to stabilize the supply voltage of microcircuits.
For troubleshooting, you will need an avometer and high-resistance headphones. After plugging the power adapter into a socket, measure the DC voltage (9 ... 14 V) at the plug-in connector plugged into the IVP (the "plus" of this voltage is on the external contact of the plug, and the "minus" is on the internal). If there is no voltage, look for malfunction: first of all, a break in the wires of the connecting cord, and if they are intact, in the transformer. If there is voltage, connect the connector to the TRS, turn it on and check if there is supply voltage (+5 V) on the corresponding pin of the connector board.
On fig. 1 shows a view of it from above with the cover of the IVP removed; here: 1 - network adapter connector; 2 - socket "AUDIO/VIDEO". The presence of voltage indicates that the 7805 microcircuit voltage regulator is working. Otherwise, make sure that there is this voltage at pin 3 of the microcircuit (Fig. 2, a) and a voltage of 9 ... 14 V at its pin 1 (both are relative to pin 2). The absence of voltage at pin 3 in the presence of voltage at pin 1 indicates that the microcircuit is out of order and needs to be replaced (it is permissible to use domestic KR142EN5A, KR142EN5V).
If there is a voltage of +5 V on the processor board, connect a modulator, a TV set, a cartridge, and a known-good joystick to the IVP. Turn on the IVP and start the game by pressing the "Start" button on the joystick. If the game starts, the repair is complete, otherwise the troubleshooting will have to continue.
Suppose after starting the game there is no image on the TV screen (both high and low frequencies), or there is an image, but no sound. In the first case, it is necessary to check whether there is a VIDEO signal on the corresponding pins of the board (Fig. 1) and the "AUDIO/VIDEO" socket (Fig. 2b). The presence of this signal can be judged by the characteristic rumble with a frame rate in the headphones connected to these contacts and the common wire (GND). Similarly, the corresponding contacts control the AUDIO signal.
Next, they check whether the VIDEO signal reaches pin 20 of the KA2197D (СХА1145Р) chip. After making sure that there is a voltage of +5 V at its pins 12 and 19 (relative to pins 1 and 24), connect the headphones to pin 20 and a common wire (GND). If no frame rate rumble is heard, the chip is faulty and should be replaced. In the absence of a microcircuit, it is possible to use the signals R, G, B and SYN (they are connected to pins 2, 3, 4 and 10 of the microcircuit, respectively), which are fed to a TV that has such an input.
The presence of the AUDIO signal is checked at pin 9 of this microcircuit. In the absence of a signal, in some cases (if there is a break in the circuit of this output), it is permissible to connect it to output 8, as a result of which the sound accompaniment is restored.
To "diagnose" the wires of the joystick connecting cable using an ohmmeter, you can use the connection diagram shown in fig. 3 (a fragment of the joystick board is shown from the mounting side of the droplet chip, and the socket is shown from the mounting side of the counterpart).
Author: E.Zheleznov, Gornozavodsk, Perm region
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