I have this machine in for repair. On one channel the output amp is totally destroyed. All the Semiconductors are completely useless. I have already installed new resistors and capacitors - no point even discussing whether they were worth salvaging.
I do not believe in buying old-stock semiconductors, as I have been burned by counterfeits too many times, and I do not have the time to waste installing parts, only to find that it's not as was advertised. Therefore ALL my repairs are now done ONLY with currently available genuine parts sourced from Mouser or Digikey. There is not a large non-SMD selection any more.
This brings me to the current problem.
There are 2 driver transistors MPSU05 NPN and MPSU55 PNP - no problem to match them and install.
The 2 NPN output amp transistors - I selected BD809's instead of the original 2N5492's.
On the good channel, the 2N5492 HFe's are 80 and 100 - close enough.
The BD809 HFe's are 500 - all 50 of them.
I contacted OnSemi Technical, expressed my surprise at measuring such a high HFe on a Power Transistor, and the rep replied that as there is no maximum HFe specified, that they meet specs.
For reference, I have the complementary PNP BD810's, and their HFe is 150.
So now I have to make do with these High HFe BD809's.
What do I need to be careful with when installing these into the circuit?
Do I need to make changes in the resistors in the circuit, or just install them, and do the normal Bias current adjustment?
See attached schematic.
Thanks
M Yachad
I do not believe in buying old-stock semiconductors, as I have been burned by counterfeits too many times, and I do not have the time to waste installing parts, only to find that it's not as was advertised. Therefore ALL my repairs are now done ONLY with currently available genuine parts sourced from Mouser or Digikey. There is not a large non-SMD selection any more.
This brings me to the current problem.
There are 2 driver transistors MPSU05 NPN and MPSU55 PNP - no problem to match them and install.
The 2 NPN output amp transistors - I selected BD809's instead of the original 2N5492's.
On the good channel, the 2N5492 HFe's are 80 and 100 - close enough.
The BD809 HFe's are 500 - all 50 of them.
I contacted OnSemi Technical, expressed my surprise at measuring such a high HFe on a Power Transistor, and the rep replied that as there is no maximum HFe specified, that they meet specs.
For reference, I have the complementary PNP BD810's, and their HFe is 150.
So now I have to make do with these High HFe BD809's.
What do I need to be careful with when installing these into the circuit?
Do I need to make changes in the resistors in the circuit, or just install them, and do the normal Bias current adjustment?
See attached schematic.
Thanks
M Yachad
