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Transistor Identification Help
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Robbie010:
Hi all,

I'm currently trying to identify the components on an old amplifier circuit so that I can try and draw up a schematic, but I'm struggling to indentify some transistors.

The markings on them read as follows:

MHPS L01

MHPS L51

BF2 45A M131

F420 PH5N

They all look pretty much the same as per the attached picture but can anyone tell me the correct values for these transistors??

Thanks in advance.
helius:
MPSL01
MPSL51
BF245A
BF420
Mortymore:
See if this make sense on your circuit:

MPSL01 NPN

MPSL51 PNP

BF245A JFET-N

BF420 NPN high-voltage
Robbie010:
Thats excellent, thank you very much!! :-+

I am yet to fully test the components but, assuming the transistors are all functioning properly would there be any benefit to swap these out for a modern replacement whilst I've got the amp stripped down?

I note that some of the transistors are now obsolete so would there be a benefit to swapping the out for modern replacements?

Thanks again.
Mortymore:
You actually may be forced to move to compatible replacements if you can't find the original references.

My advise is, since it's an audio amplifier, the transistor replaced in the right/left channel  should be replaced on the other channel also. It would be even better, even if it's just one transistor needed to be replaced, that you buy not only one for each channel, but a few more and try to match a pair of them with the same gain (hfe), so you wont end up with unbalanced right/left channels.
Try to put the amplifier working, first of all. Next you can play (an educated play) with different components to achieve better results.

Good luck.
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