SONY TA 70, repair help needed

jojospecial · 5th November 2008, 11:25 AM

Hello to all the experienced electronic enginneers on this forum.
I need your help to get started on repairing a Sony TA 70 mini-amp from the 70's.
I bought it from e-bay becouse I love vintage hi-fi, and I worked fine for a little while.
With the habbit of leaving the bedroom system playing all night long I woke up one morning and the amp was producing music just like it would be if someone took the output signal and passed it through a very low frequency amplitude modulation.
The sound comes out undistorted but the amplitude follows a sine wave. In the lowest ouput the sound chokes to nothing, and the again the output starts getting higher to peak defined by the volume setting, from which it descents to null again.
I have not faced such a problem again, and I am calling for help.
Thanks in advance for the time spent on my problem by anyone out there.

sakis · 5th November 2008, 02:25 PM

to my shop for repair .....

i will charge nothing for forum memebrs of course ....

the only thing i am going to do is to show you what to do and ofcourse provide all my instruments for the testings

friendly regards sakis

jojospecial · 5th November 2008, 08:15 PM

Thanks for the offer. As soon as I have some spare time, I'll come by.

5th November 2008, 11:25 AM	#1
jojospecial diyAudio Member Join Date: Aug 2008	SONY TA 70, repair help needed Hello to all the experienced electronic enginneers on this forum. I need your help to get started on repairing a Sony TA 70 mini-amp from the 70's. I bought it from e-bay becouse I love vintage hi-fi, and I worked fine for a little while. With the habbit of leaving the bedroom system playing all night long I woke up one morning and the amp was producing music just like it would be if someone took the output signal and passed it through a very low frequency amplitude modulation. The sound comes out undistorted but the amplitude follows a sine wave. In the lowest ouput the sound chokes to nothing, and the again the output starts getting higher to peak defined by the volume setting, from which it descents to null again. I have not faced such a problem again, and I am calling for help. Thanks in advance for the time spent on my problem by anyone out there.

5th November 2008, 02:25 PM	#2
sakis diyAudio Member Join Date: Jan 2006 Location: nea makri athens greece	you can bring it ..... to my shop for repair ..... i will charge nothing for forum memebrs of course .... the only thing i am going to do is to show you what to do and ofcourse provide all my instruments for the testings friendly regards sakis __________________ SERVICE ΙΑΠΩΝΙΚΩΝ ΜΗΧΑΝΗΜΑΤΩΝ ΗΧΟΥ www.eastelectronics.gr

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5th November 2008, 08:15 PM	#3
jojospecial diyAudio Member Join Date: Aug 2008	Thanks for the offer. As soon as I have some spare time, I'll come by.

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