Seems a well known problem: https://www.diyaudio.com/community/threads/technics-se-a100.301090/post-4925914
KCT is right.
Still waiting for replacement parts.
I'll keep you informed.
KCT is right.
Still waiting for replacement parts.
I'll keep you informed.
So finaly all is well..
Sourcing the replacement transistors took a lot time and effort (incl. fake China power trans...) OK I've been warned 🙄
Beware of ebay seller globewin concerning at least Toshiba transistors.
Original: Non magnetic, weight 9.4 gr.
Fake : Magnetic, weight 7.1 gr.
At the end I ordered at digikeys...
The smaller ones at different vendors.
All transistors had been matched by me.
Left/ right and NPN/ PNP.
I like this amp very much. To me it sounds nicer than my NCores and Abletec Anaview ALC 1000-1300.
If someone experience the same problems with this amp (popping noises after some time running, current amp bias not adjustable):
Replace the small transistors on the voltage controll amp and change R147- 150 from 100 to 460 ohm. Or place heat-fins on at least Q115 -Q121 and on the 2SA1309s.
And if you can't adjust the bias on the current amp board, check Q151 and Q152.
On my board one side didn't change bias,
although adjusting the trim pot. At the end Q151 was defect.
The BOM states the classifications of all transistors, so matching hfe ist a good thing.
Thanks a lot for your support.
Sourcing the replacement transistors took a lot time and effort (incl. fake China power trans...) OK I've been warned 🙄
Beware of ebay seller globewin concerning at least Toshiba transistors.
Original: Non magnetic, weight 9.4 gr.
Fake : Magnetic, weight 7.1 gr.
At the end I ordered at digikeys...
The smaller ones at different vendors.
All transistors had been matched by me.
Left/ right and NPN/ PNP.
I like this amp very much. To me it sounds nicer than my NCores and Abletec Anaview ALC 1000-1300.
If someone experience the same problems with this amp (popping noises after some time running, current amp bias not adjustable):
Replace the small transistors on the voltage controll amp and change R147- 150 from 100 to 460 ohm. Or place heat-fins on at least Q115 -Q121 and on the 2SA1309s.
And if you can't adjust the bias on the current amp board, check Q151 and Q152.
On my board one side didn't change bias,
although adjusting the trim pot. At the end Q151 was defect.
The BOM states the classifications of all transistors, so matching hfe ist a good thing.
Thanks a lot for your support.
Attachments
