Hi
This amp was on standby and not powering up. Upon checking Q201(relay drive) was open. After replacing the transistor, the amp turned on as normal. Some of the input source (tuner,tape1) were not functioning. Upon inspecting the front board, I realise that the solder joints were bad, so I took out the front board and resoldered the whole board. After reassembling, the amp does not turn on. It is on standby again. There is 5V present on pin34(Vdd) of the cmos microproccesor, but no voltage on pin80(standy relay). No voltage on pin80 means no base voltage for Q201, the relay drive. I am not familiar with CPUs, and wonder what could have gone wrong. I have checked Q201 and all other components on the power supply board, they are OK. Could the CPU itself be the problem. Pls assist.
Thanks
This amp was on standby and not powering up. Upon checking Q201(relay drive) was open. After replacing the transistor, the amp turned on as normal. Some of the input source (tuner,tape1) were not functioning. Upon inspecting the front board, I realise that the solder joints were bad, so I took out the front board and resoldered the whole board. After reassembling, the amp does not turn on. It is on standby again. There is 5V present on pin34(Vdd) of the cmos microproccesor, but no voltage on pin80(standy relay). No voltage on pin80 means no base voltage for Q201, the relay drive. I am not familiar with CPUs, and wonder what could have gone wrong. I have checked Q201 and all other components on the power supply board, they are OK. Could the CPU itself be the problem. Pls assist.
Thanks
An accidental short in the resoldering process?
Or also likely, more cold joints on other boards.
Hugo
Or also likely, more cold joints on other boards.
Hugo
Prior to that I have resoldered the other boards as well. After resoldering the other boards, the amp did turn on as normal. I removed this board from rest of the circuit before soldering. I totally isolated it.
Thanks
Thanks