AC in: supply power for the small PSU which provide 12V to the CPU board. This 12V also supply the voltage to the coil of the Relay through a Resistor bought it down to 9V. One of the AC input line (L) will go to one pin of the Relay and waiting there until the Relay closed, when this happens, the AC will be supply to the Main Transformer, supply voltages to everywhere else. The 9VDC goes through the Relay coil and come to the Collector of the 9002 transistor and waiting there. When the power on button is pushed, a voltage will be sent to the Base of this transistor to turn it on and the current will flow from its Collector to Emiter to the Ground and energize the Relay coil (the circuit is closed). Which in turn will close the AC in contact of the Relay and everything start working. You did not measure correctly when you tried to find out 12V at the beginning (wrong ground pin). 9V or 12V always present on both side of the Relay's coil. It only waiting to be connected to the ground to make a complete circuit through the 9002 transistor (acting like a switch). With this Receiver, the line from the Relay coil to the Collector of the 9002 was broken, so it will not complete a circuit does not matter if the transistor working or not.
I did not measure the wrong ground point at the start. I tested 12v & ground coming up that connection lead, which is the power supply powering the CPU, I then tested between 12v & powerd to find out if the relay was getting powered. I may not have measured as some academic may have wrote in a service manual, but my measurments told me what I needed to know. Was the relay getting activated? (it wasn't). So then I tested the circuit which activates the relay, the Apower signal from the CPU & the 9002 transistor. There was one thing wrong in the video, I mixed up the Emitter & Collector pins on the 9002 transistor. I was checking why the relay wasn't getting activated, so it did matter if the transistor was working. Sure the track was broken between 9002 and PowerD, but if I repaired that and the transistor was blown, it still wouldn't have activated the relay.
AC in: supply power for the small PSU which provide 12V to the CPU board.
This 12V also supply the voltage to the coil of the Relay through a Resistor bought it down to 9V.
One of the AC input line (L) will go to one pin of the Relay and waiting there until the Relay closed, when this happens, the AC will be supply to the Main Transformer, supply voltages to everywhere else.
The 9VDC goes through the Relay coil and come to the Collector of the 9002 transistor and waiting there. When the power on button is pushed, a voltage will be sent to the Base of this transistor to turn it on and the current will flow from its Collector to Emiter to the Ground and energize the Relay coil (the circuit is closed). Which in turn will close the AC in contact of the Relay and everything start working.
You did not measure correctly when you tried to find out 12V at the beginning (wrong ground pin). 9V or 12V always present on both side of the Relay's coil. It only waiting to be connected to the ground to make a complete circuit through the 9002 transistor (acting like a switch).
With this Receiver, the line from the Relay coil to the Collector of the 9002 was broken, so it will not complete a circuit does not matter if the transistor working or not.
I did not measure the wrong ground point at the start. I tested 12v & ground coming up that connection lead, which is the power supply powering the CPU, I then tested between 12v & powerd to find out if the relay was getting powered.
I may not have measured as some academic may have wrote in a service manual, but my measurments told me what I needed to know. Was the relay getting activated? (it wasn't).
So then I tested the circuit which activates the relay, the Apower signal from the CPU & the 9002 transistor.
There was one thing wrong in the video, I mixed up the Emitter & Collector pins on the 9002 transistor.
I was checking why the relay wasn't getting activated, so it did matter if the transistor was working. Sure the track was broken between 9002 and PowerD, but if I repaired that and the transistor was blown, it still wouldn't have activated the relay.