Beta Group (Hfe) of replacement transistors
 

I'm replacing a pair of shorted outputs in an Onkyo TX-SV525 AV
Receiver. The manual states, "Replacements must be from the same beta
group (Hfe) as the original type". This has something to do with the
devices' gain, I suppose. The originals are marked "Toshiba B1557 O 5H"
and "Toshiba D2386 O 5G". MCM Electronics has 2SB1557 and they sub
2SD2386 to 2SD2387. Assuming I properly replace all the other faulty
components in the failed channel's output stage, what's likely to
happen when I power this unit up with sub's that most likely have
different Hfe than the originals? Thanks for any thoughts.

As long as you "caught" all the other likely faults and faulty
components like shorted diodes, open low ohm resistors, electrolytics,
driver transistors, cracked solder connections, etc, etc,.. then your
Onkyo amp will power up just fine even with transistors that are not
exactly beta matched.... the final product might be distortion numbers
that are very slightly off spec but not really a big problem. Put in
the transistors that you have, doublecheck for other related failures
and cross your fingers and power it up, if they blow again, it is NOT
the output transistors that you installed, it would mean that you
missed something. .... otherwise, enjoy the music.
electricitym
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