TV GRUNDIG-GR1450 stopped to switch from operating mode to standby (STANDBY) on command from the remote control when you press the ON/OFF button.
Part of the circuit node that performs the command shown in the picture (reference designators specified in accordance with the scheme of the TV).
Let us briefly examine his work. The signal from the remote control, adopted a working TV is processed by a specialized microcontroller CTV222S-PRC1 (U101). On his the STDBY output (pin 41) you receive the high voltage, which opens the transistor Q103. In turn, this leads to the closing of the transistor Q505 and, consequently, transistor Q506 and Q507. As a result, the voltage +115 In ceases to flow through the transistor Q507 on the output stage horizontal and the TV switches to standby mode.
The audit showed that out of order transistor Q506. It was "broken" the collector junction. In this case, the transistor Q507 remained open regardless the signal level at the output STDBY microcontroller.
After you replace a failed device operability of the TV was restored, but not for long. The second TV power off command from the remote control again took out the same transistor. The same fate befell another instance. It became clear that the transistor operates in the regime close to the limit (most likely, the permissible power dissipation at the collector output), and when transients resulting from the shutdown of the supply voltage horizontal, power generated in the power transistor exceeds the limit allowed and he breaks down.
Obviously, it was necessary to choose a transistor structure p-n-p with parameters no worse than 2N5401 and greater power dissipation. Such a device has been found. This is domestic CTA. After you install the performance of the TV fully recovered.
Author: Vladimir Chudnov