Sansui AU719 protection relay repair....please help!

[Beau Geste]

Do you have the service manual? You can find it here :https://www.hifiengine.com/manual_library/sansui/au-719.shtml.. I will check the driver stage...

 

[petehall347]

we are homing in on it ..tr11 is in trouble or a resistor around there . i have other thoughts too .possible shorted capacitor c14 c15 .

 

[mcgreg66]

R31 58 Ohm

 

[petehall347]

best test tr11 .

 

[mcgreg66]

Solder out and test?

 

[petehall347]

Solder out and test?

that is best way but i would test in circuit first .

 

[mcgreg66]

How I should do testing?!

 

[petehall347]

6 way test .use diode test function on your meter ..
http://audiokarma.org/forums/index.php?threads/bipolar-junction-transistor-testing-basics.43186/

 

[petehall347]

http://audiokarma.org/forums/index....-transistor-testing-basics.43186/#post-432830

 

[mcgreg66]

TR11 right channel tests like this.....
B-E 640
B-C 640
C-E 1890
C-B 1990
E-C 870
E-B 930
And TR11 left channel tests nearly exact the same....
Should be alright? Or not?!

 

[petehall347]

yes at least it isnt shorted .
its late here so cant concentrate too well right now . if you could test resistors values in that general area in the meantime .
tr10 tr11 collector voltages are telling us something put cant put my finger on it right now . might be a transistor . give them all a quick in circuit test . pull and test again if any look bad .

 

[petehall347]

quick note you could check resistance between tr10 tr11 collectors .

 

[mcgreg66]

Don’t want to keep you up.....
Just answer if you have time.
CTr10 - CTr11 56Ohm
Checked C15 correct 1uf and C14 is 46nF
I will check transistors and resistors around and compare to left channel

Good night!

 

[petehall347]

sorry but had to do this ..

 

[petehall347]

p.s not connected to the thread at all ..

 

[mcgreg66]

Hey Pete,
I tested all transistors left and right channel and compared all readings.
Same with all resistors - they all read the same.
The only suspect to me was TR10
TR10 left/right
BE 816/ -
BC -/-
CE 910/ -
CB 635/650
EC - / 1300 going up
EB 630/680

I pulled it out and tested again - hfe 132 - seems low for me but I don’t have comparison!
I can try to get recommended substitute KSA1381 or KSC3503
What do you mean- Worth a try or how to goon?

 

[mcgreg66]

What about transistors with testing E to C low but climbing up and up to no reading?!

 

[petehall347]

What about transistors with testing E to C low but climbing up and up to no reading?!

capacitor in circuit charging up

 

[petehall347]

[QUOTE="What do you mean- Worth a try or how to goon?[/QUOTE]

lost me there

 

[petehall347]

r17 820 ohms may be open
c16 might be bad .