Help with an amp, turns on but no sound

[HeavyD'sCustom]

Originally posted by Perry Babin
Are you sure the fuse isn't blown?

If not, you probably have a broken solder connection between the B+ connector and the power transformer. The inductor is a prime suspect.

OK u are right, so power didnt go from one end of the straight one to the other. So I took it off the board it one end wasn’t soldered anymore, so I re-soldered it in.

And here is the is what I got off of the 4 transistors:

the first two:
Pin 1: 0.0
Pin 2: 12.0
Pin 3: 0.0

the second two:

Pin 1: 2.33
Pin 2: 2.64
Pin 3: 2.33

[Perry Babin]

What are the numbers on the faces of these 4 transistors?

[HeavyD'sCustom]

Originally posted by Perry Babin
What are the numbers on the faces of these 4 transistors?

#1 - LRF**4 - could not read good - even tried
#2 - LRF**4 - magnifier with light.
#3 - C2500
#4 - BY028E

[Perry Babin]

Do the transistors look like they are the original parts?

Are you looking at the 4 on the left (two top, two bottom)?

Could the numbers be IRFZ44?

Sometimes, if you rub some of the white heatsink compound on the face of the transistor, it makes it easier to read the numbers.

With the amp powered up and the black probe on a non-bridging speaker terminal, what is the DC voltage on the center legs of the large output transistors?

[HeavyD'sCustom]

Originally posted by Perry Babin
Do the transistors look like they are the original parts?

Are you looking at the 4 on the left (two top, two bottom)?

Could the numbers be IRFZ44?

Sometimes, if you rub some of the white heatsink compound on the face of the transistor, it makes it easier to read the numbers.

With the amp powered up and the black probe on a non-bridging speaker terminal, what is the DC voltage on the center legs of the large output transistors?

ok Here is how i was #ing them, tell me by the # on the pic so we are on the same page(transistor).

Thanx D

[HeavyD'sCustom]

Oh and i did reinstall the # 10 transistor.

[Perry Babin]

1, 2, 5 and 6 are the power supply FETs (from what I can tell).

3 and 4 are the rectifiers.

7, 8, 9 and 10 are the output transistors.

When you measure the voltage on 1, 2, 5 or 6, you need to have the black probe on the chassis ground terminal. When you're measuring the voltage on the rest of the transistors/rectifiers, you need to place the black probe on a non-bridging speaker terminal.

[HeavyD'sCustom]

ok new readings.

1 - 2 - 5 - 6:
Pin 1: 0.0
Pin 2: 12
Pin 3: 0.0

3:
Pin 1: 0.0
Pin 2: 0.66
Pin 3: 0.0

4:
Pin 1: 0.0
Pin 2: 0.31
Pin 3: 0.0

7 - 8:
Pin 1: 0.28
Pin 2: 0.66
Pin 3: 0.09

9 - 10:
Pin 1: 0.28
Pin 2: 0.31
Pin 3: 0.28

[Perry Babin]

Post the DC voltage on the pins of the TL494. Black probe on chassis ground. Amp powered up.


Pin 1:
Pin 2:
Pin 3:
Pin 4:
Pin 5:
Pin 6:
Pin 7:
Pin 8:
Pin 9:
Pin 10:
Pin 11:
Pin 12:
Pin 13:
Pin 14:
Pin 15:
Pin 16:

[HeavyD'sCustom]

Ok the # on that chip is KIA494P

Pin 1: 0.01
Pin 2: 4.9
Pin 3: 4.95
Pin 4: 0.20
Pin 5: 2.0
Pin 6: 3.54
Pin 7: 0.0
Pin 8: 12.1
Pin 9: 0.0
Pin 10: 0.0
Pin 11: 12.1
Pin 12: 11.24
Pin 13: 5.03
Pin 14: 5.03
Pin 15: 5.03
Pin 16: 9.73