Sony TA-F5A Power Transistor Replacement

[jjbunn]

My Sony TA-F5A amplifier has two blown power transistors on the left channel - they present as shorts emitter to collector. These are Q312 and Q313 on the attached schematic ... types 2SA771 and 2SC1986C-O respectively.

I have ordered 5 pairs of MJE15033G/MJE15032G as replacements (following a recommendation on another thread at AudioKarma). I'd welcome some advice on my options:

• Replace just the two blown transistors with MJE
• Replace all four transistors on the left channel with MJE
• Replace all eight transistors so both channels have the same MJE types throughout.

Thanks!

 

[sregor]

Replace 4 in one channel. When you have parallel output transistors, the amp is always happier if they are similar characteristics - if they are too different, one ends up doing all the work, and usually doesn't last. IMHO topology is more important than individual components in amplifier circuits, so matching the two channels isn't necessary, although many people do it. My 2 cents.

 

[daybreak2350]

If cost is not a concern, I'd replace 'em all "in one fell swoop". This presumes that the new transistors will last longer than the existing original ones.
However, were I a repair shop I'd probably replace just the bad transistors to "fix" the amp. That way you'd have to bring it back in again if/when other old transistors fail--thereby increasing my profits! ...

 

[jjbunn]

Thanks, guys ... I think I'll go with Steve's suggestion to replace the four in the same channel.