Crossfire CFA602

[mike49504]

This amp wont power up heres the voltages on the 494

1:0
2:4.93
3:.05
4:4.93
5:1.43
6:3.59
7:0
8:13.93
9:0
10:0
11:13.93
12:13.93
13:4.92
14:4.93
15:4.93
16:0

[Perry Babin]

Have you replaced any components?

Have you checked the outputs?

[mike49504]

Havent repalced anything yet . Outputs test fine in the board i havent taken them out to check for leakage yet. Power light comes on for a sec then shuts right off

[Perry Babin]

Pin 4 is being driven high. Follow the circuit back to see if you can find what's driving it.

[mike49504]

I see a Transistor A1266 that goes to pin 4 I will test that and see what i come up with.

[mike49504]

After the transistor it goes back to a thermistor. Which measures 4.95k across it. Do i need to follow the circuit back more?

[Perry Babin]

Is the emitter of the 1266 connected to pin 14 of the 494?

If so, remove it to see if it will power up but be prepared to shut it down if the amp begins to draw excessive current.

[mike49504]

With the A1266 removed amp powers on and idles perfectly and also produces audio.

[Perry Babin]

Does the base of the 1266 connect to a transistor in the audio section (near Q130, 131, 132, 232)?

There may be a resistor in series between the transistors.

[mike49504]

Q131 connects to it. (C3198) between legs 2 and 3 i get 2.5 ohms in the board.