archiebald
New Member
Hi, just found this site and its my first post.
I have a question that I would like to ask.
I've had this Technics amp since new (1994) although it hasn't had a huge amount of use. I love it but it has started playing up in the last few months. I have some basic electronics knowledge, but no experience of this type of troubleshooting.
From power on, everything is fine - but then after anything from 10 minutes to 3 or 4 hours it starts cutting out. On the front panel, all the LED'S except the power supply go off - at the same time the power supply lamp flickers a little but never goes off. It is obvious that relays are switching off/on at the same time.
It sort of looks like it is going into protected mode, but then it resets itself coming back on almost immediately then repeats this randomly for a few seconds or minutes. According to the manual, once it goes to protected mode, it will stay there until the power is reset so I don't think this is really the case.
Sometimes, it will clear itself completely and work flawlessly for hours, other times it will keep stuttering until I power off then on again. This usually clears it for another 20 to 30 minutes.
I have tried different speaker cable and different speakers, in case there was anything triggering the protect mode.
It does this at more or less any volume setting, even playing very quiet background music.
Another symptom is that when I press one of the input buttons or speaker output (A or B) buttons, it sometimes skips to an incorrect setting. Seems as if the contacts are dirty and it is giving corrupted signals to the processor.
Sound quality is still superb, no signs of humming or buzzing even at ridiculous volume settings.
I have managed to find the schematics for the SU-A900 Mk2 which I think is almost identical in layout (just some different components). I have a suitable multimeter.
I am willing to start diving in with a soldering iron and replacing parts but would appreciate any pointers or simple tests that I can do.
I have a question that I would like to ask.
I've had this Technics amp since new (1994) although it hasn't had a huge amount of use. I love it but it has started playing up in the last few months. I have some basic electronics knowledge, but no experience of this type of troubleshooting.
From power on, everything is fine - but then after anything from 10 minutes to 3 or 4 hours it starts cutting out. On the front panel, all the LED'S except the power supply go off - at the same time the power supply lamp flickers a little but never goes off. It is obvious that relays are switching off/on at the same time.
It sort of looks like it is going into protected mode, but then it resets itself coming back on almost immediately then repeats this randomly for a few seconds or minutes. According to the manual, once it goes to protected mode, it will stay there until the power is reset so I don't think this is really the case.
Sometimes, it will clear itself completely and work flawlessly for hours, other times it will keep stuttering until I power off then on again. This usually clears it for another 20 to 30 minutes.
I have tried different speaker cable and different speakers, in case there was anything triggering the protect mode.
It does this at more or less any volume setting, even playing very quiet background music.
Another symptom is that when I press one of the input buttons or speaker output (A or B) buttons, it sometimes skips to an incorrect setting. Seems as if the contacts are dirty and it is giving corrupted signals to the processor.
Sound quality is still superb, no signs of humming or buzzing even at ridiculous volume settings.
I have managed to find the schematics for the SU-A900 Mk2 which I think is almost identical in layout (just some different components). I have a suitable multimeter.
I am willing to start diving in with a soldering iron and replacing parts but would appreciate any pointers or simple tests that I can do.
