Rockford Fosgate 100x2

[fongman]

I think i found it. Right next to the bias on that channel.

 

[Perry Babin]

From the screen cap, Q221 appears OK (assuming that it was checked in the board).

Check R265. Is it within tolerance?

If so, pull Q212. Does the amp still have positive rail voltage on the speaker terminal (black probe on chassis ground)?

 

[fongman]

I got 20.1 ohms on R265. With Q212 out i got 3.6v.

 

[Perry Babin]

With the amp powered up and the black probe on chassis ground, post the DC voltages on Q219, 220 and 224. For the SMD transistor, the pins are 1 and 2 on the bottom (left to right) with 3 on top.

Q220
Leg 1:
Leg 2:
Leg 3:

Q219
Leg 1:
Leg 2:
Leg 3:


Q224
Leg 1:
Leg 2:
Leg 3:

 

[fongman]

Should i put q212 back 1st?

 

[Perry Babin]

No.

 

[fongman]

Q220
Leg 1: 32.5v
Leg 2: 32.02v
Leg 3: 32.54v

Q219
Leg 1: 32.04v
Leg 2: 3.60v
Leg 3: 32.54v


Q224
Leg 1: 32.04v
Leg 2: 3.60v
Leg 3: 32.54v

 

[Perry Babin]

Check Q212. Use the link above the one you used to check the SMD transistor and send me the screen cap.

 

[Perry Babin]

With 212 out of the circuit, what is the DC voltage on it's solder pads (square solder pad = pin 1)?

Q212 pads
Pin 1:
Pin 2:
Pin 3:

What is the voltage on the terminals of Q202 and Q203 (see attached for layout)?

Q202
Pin 1:
Pin 2:
Pin 3:

Q203
Pin 1:
Pin 2:
Pin 3:

 

[fongman]

Q212 pads
Pin 1: .89v
Pin 2: 14.47v
Pin 3: 31.90v


Should i test Q202 and Q203 with the black on the amp ground?

 

[fongman]

I test this with the black on amp ground and red on the Q212 pins. Is this right?

Q212 pads

Pin 1: .089v
Pin 2: 14.48v
Pin 3: 31.90v

 

[Perry Babin]

Touch the black probe to chassis ground for all of these.

 

[fongman]

Q202
Pin 1: 1.524v
Pin 2: .929v
Pin 3: 13.79v

Q203
Pin 1: 2.00v
Pin 2: .801v
Pin 3: 14.53v

 

[Perry Babin]

It appears that Q203 could be defective. What's the DC voltage measured directly across R220 and R221?

 

[fongman]

I'v got 2.01v and .810v from them

 

[Perry Babin]

Is that measured with the probes directly across the resistors?

 

[fongman]

Directly across q203.

 

[Perry Babin]

directly across R220 and R221

 

[fongman]

Yes the pin 1 and 2 are across from the two 510 resistor.

 

[Perry Babin]

See attached. You need to measure the DC voltage across the 33 ohm resistors (R220 and R221). This is NOT a 100x2 but it's the closest that I have in the shop.