Hi I have just joined the forum and new to this . I am trying to repair my Yamaha AX 700 . I have the left channel working . I have ran comparisons against the right ch. which keeps blowing the outputs , driver and predriver transistors. I have noticed that the dc . voltages on the emitters and base of the working channel as well as the blown channel pulses.The collectors are stable at -64 and +64 . any one has any suggestions
Regards,Jeeva
South Africa
Regards,Jeeva
South Africa
Hi Jeeva
Where did you buy your replacement transistors? Are you aware of the proliferation of counterfeit transistors? See here Counterfeit Transistors .
What are the device types?
Where did you buy your replacement transistors? Are you aware of the proliferation of counterfeit transistors? See here Counterfeit Transistors .
What are the device types?
We would have to see a circuit.
Also always use a bulb tester in the mains lead... it will avoid destroying transistors.
Also always use a bulb tester in the mains lead... it will avoid destroying transistors.
yamaha Ax 700
Hi shaun ,thanks for the reply and my thanks to Ebbe for the schemastics.
I have purchased the output transistors from a supplier here in Durban ,South Africa. Yes I have heard from Jim in Madrid about the suspicious components been supplied worldwide. I have been directed to a company in Johannesburg to repurchase my components needed, Your suggestion about the spares used been faulty is believable ,since all measurements against the working channel seem okay. I will be getting the new spares on Monday . I will keep you posted
Best regards,
Jeeva
Hi shaun ,thanks for the reply and my thanks to Ebbe for the schemastics.
I have purchased the output transistors from a supplier here in Durban ,South Africa. Yes I have heard from Jim in Madrid about the suspicious components been supplied worldwide. I have been directed to a company in Johannesburg to repurchase my components needed, Your suggestion about the spares used been faulty is believable ,since all measurements against the working channel seem okay. I will be getting the new spares on Monday . I will keep you posted
Best regards,
Jeeva
The problems you describe mirror my experiences with fake transistors. I do not trust the local outlets such as Communica, etc. Perhaps the official distributors are a better bet, but they usually demand minimum order quantities such as a full stick of 25 devices. For Sanken devices I finally resorted to importing.
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