Lighting Audio B2-300.4

[mike49504]

I must be off my game today. I cant figure this amp out. The amp is stuck in protection mode So i pulled the rectifiers and outputs Amp is still in protection mode.

This is the voltages i got

Tl494
1:0.13
2:0.50
3:.07
4:0
5:0
6:0
7:0
8:1.45
9:0
10:0
11:1.45
12:1.46
13:0.69
14:0.69
15:0.68
16:0

Power supply fets irfz44
1:0
2:13.91
3:0

Any ideas on where to check?

 

[Perry Babin]

Follow the circuit back from pin 12 to a PNP transistor (Q2?). If you can't determine if the transistor is defective, post the voltage on it.

 

[mike49504]

Q2: 2n4403

1:1.43

2:2.78

3:0

 

[Perry Babin]

The problem is farther back. The emitter should be near 12v (if the collector is connected to pin 12). Follow it back to see why the emitter doesn't have 12v.

 

[mike49504]

it goes back to another 2n4403 and thoose voltages are

1:13.91
2:10.59
3:1.44

do i need to track it back farther then that yet?

 

[Perry Babin]

That one is defective.

 

[mike49504]

ok yes i can see that one is defective but still have more issues im gonna follow it back some more

 

[mike49504]

Perry,

amp is still stuck in protect mode. This is what i have now

Q2:

1:13.80
2:13.80
3:0

Q3:

1:13.91

2:13.17

3:13.80

TL494

pin12:13.80

 

[Perry Babin]

Those voltages look OK. Post the voltage on all of the pins of the 494.

 

[mike49504]

TL494

1:0.98
2:3.66
3:.06
4:.03
5:1.50
6:3.39
7:0
8:11.18
9:4.60
10:4.60
11:11.18
12:13.79
13:4.99
14:4.99
15:4.99
16:0

Power supply fets
1:4.60
2:13.83
3:0

 

[Perry Babin]

It doesn't look like it's in protect mode. Did you check to see if it was producing audio?

 

[mike49504]

Ok its powerd up and producing audio Thank you.

Not to change amps on you but im working on another amp which has 2 resistors behind the speaker terminals they got hot at 1 point and only color bands i can read are green blue -- gold. It measures 5.6 on my meter A 5.6K resistor??

 

[Perry Babin]

It's probably a 5.6 ohm if it's in series with a film capacitor (~0.1uF).