Hello all,
I have an integrated ampfiler Technics SU-A700 Mk2 . It has been working well for many years but now when connected to mains it remains in stand-by and does not want to power up. Sometimes it turns on normaly and works normaly but it looks to be absolutely randomly. I did not observe any systematic behavior in this. There is the same behavior when trying to turn it on with POWER button on a panel or using remote control. Also the same with connected inputs and speakers and disconnected.
I have done a very basic diagnostic. I have checked if the speakers are not shorted - they were not, I have opened the cover hoping I'll see something evident but I haven's seen any burned parts or blown-out capacitors. I have tried to measure the voltages on the power supply's output but not aware if they are correct (34 V, 34 V, 6.5 V, 6.3 V all AC against ground). I have also checked the switch with a beeper.
So before I start a complex diagnostics and do crazy things I would like to ask here if ti's not an "old pain" of these units being so long in service or if someone had the same issue and has already resolve it. I have downloaded a service manual which shows mainly how to operate and disassemble the unit and schematics and PCBs layouts.
Thanks all in advace.
Regards
Kamil
I have an integrated ampfiler Technics SU-A700 Mk2 . It has been working well for many years but now when connected to mains it remains in stand-by and does not want to power up. Sometimes it turns on normaly and works normaly but it looks to be absolutely randomly. I did not observe any systematic behavior in this. There is the same behavior when trying to turn it on with POWER button on a panel or using remote control. Also the same with connected inputs and speakers and disconnected.
I have done a very basic diagnostic. I have checked if the speakers are not shorted - they were not, I have opened the cover hoping I'll see something evident but I haven's seen any burned parts or blown-out capacitors. I have tried to measure the voltages on the power supply's output but not aware if they are correct (34 V, 34 V, 6.5 V, 6.3 V all AC against ground). I have also checked the switch with a beeper.
So before I start a complex diagnostics and do crazy things I would like to ask here if ti's not an "old pain" of these units being so long in service or if someone had the same issue and has already resolve it. I have downloaded a service manual which shows mainly how to operate and disassemble the unit and schematics and PCBs layouts.
Thanks all in advace.
Regards
Kamil
Suspect dried capacitor all small caps must g😵r dry solder joint. Inspect and resolder all joints under board and after that check how it's going the amp prior to replace caps.
Q814 is a relay drive; its base is driven by IC801 pin 26.
Also, IC801 pin 18 (the reset pin, normally low) has two states:
1. Floating 5V
2. Low, when the Q815 is conducting
... you should check that as well... IC802 controls the reset function
Good luck.
Also, IC801 pin 18 (the reset pin, normally low) has two states:
1. Floating 5V
2. Low, when the Q815 is conducting
... you should check that as well... IC802 controls the reset function
Good luck.