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Sony TA-F3A repair

R

rosaage

New Member
Hello, I'm new here.
I have an old Sony TA-F3A i got from my mom, but unfortunately it's not working. When I power it on one of the two fuses blow instantly, and one of the diodes (D303) becomes very hot. I found some diagrams for it here: http://elektrotanya.com/sony_ta-f3a.pdf/download.html
But it's too advanced for me :(
I'll bring home my multimeter tomorrow so I can to some testing, but I'm not really sure what to test.
 

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first start with checking the diodes ..you might be lucky and its just one or 2 gone short ..
next step if they are ok is checking the output transistors ..
word of warning don't power it up with the outputs not screwed down to the heat-sink .. they will cook real fast .and make sure the mica insulators are installed and insulators on the screws
 
I tried the measuring the diodes but they gave around 0,5 both ways. Does this mean they are bad or is it because of something else they are connected to? should i try removing them?
I also tried testing the 4 transistors connected to heat sinks, one of them a A771 PNP seems to have a short, my meter gives a continuous beep between the base and the two others.
and one a C1986 NPN gives 0,172 between base and emitter and base and collector. And gives the exact same readings when reversing (negative on base)
according to this http://www.audiokarma.org/forums/showthread.php?t=43186 it should read around 0.45 to 0.65V so this seems a bit low.
Both transistors have a short between collector and emitter.

Should I order replacements for these two or remove them and test?
 
Seems like there were a bit more than just the transistors. After i replaced the two bad transistors the new ones got fried instantly. One of them cracked in the middle and split in 3 parts. But i picked up a "National Panasonic RE-7860LBS" to use instead so I probably won't try fixing this sony amp any more.

Sent from my GT-I9305 using Tapatalk
 
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