SONY TA-F319R amp problem

[Joe Black]

Have a weird issue with this one:

Amp doesn´t allow me to select ANY input.
When I press input selector button (AUX, TUNER, ie), that LED lights, but only while the button is pressed. When I release it, LED goes off, and amp doesn`t work (since there`s no input selected I guess).

How can I determine if that´s a selector problem, or protection is activated or maybe something else?
When I leave it on, output transistors remain completely cold.

SM : https://www.manualslib.com/manual/11...9r.html#manual

[R_J]

Re: SONY TA-F319R amp problem

After you turn the amp on do you here the speaker relay click? Check that you have + & - 37 volts on the large capacitors, then check that you have close to zero volts on R525,R526,R625,R626 emitter resistors.
Next check that you have +9 volts on ic902 (3) and -9 volts on ic903 (3)
Also check that the 5 volts coming from IC901(5) is ok.

[Joe Black]

Re: SONY TA-F319R amp problem

I think it clicks, but really hard to tell. ON large caps (both) 40V.

emitter resistors all close to zero, but IC 902 and 903 are real fun.

IC902 input 60V, output 24V.
IC903 input 3,8V, output 3,0V.

According to schematics both should be near 20v input \ 8V output.

Weird things at work here

[Joe Black]

Re: SONY TA-F319R amp problem

Found out that IC 902 & 903 have been changed by someone, and while they are same type, pin order is different.

After rewiring, I have 8V on the one side, but 37 on the other (same as the input)

I´ll order new regulators and go from zero.