Rockford 800.2

[imraneesa]

Hi

I fixed power supply. It had a mosfet bad. Now amp comes on a d has all the voltages. Signal is good until R201. After that the signal is very weak on outputs. Tested all transistors but everything looks good. Does it have mute signal any where.

 

[Perry Babin]

Short Q11 C-E with a jumper and power up through a limiter. Does the amp produce audio at a normal level?

 

[imraneesa]

Short Q11 C-E with a jumper and power up through a limiter. Does the amp produce audio at a normal level?

Yes amp came on with 1.7amps with limiting resistor and got 15v rms output signal on speaker terminals and it is 100hz signal it is clean.

 

[imraneesa]

One channel is pulling current mostly irf9640 0.1 ohm resistor is have 6.8 millions. On one resistor when I remove that mosfet other resistor now having 6.8 to 7 milliohms. I removed all 9640 except one and this mosfet resistor also having same value. Other side channel only has 0.2milliohm. Bias pot turned all to anti clock side.

 

[Perry Babin]

What's the PC# for this amp?

 

[imraneesa]

What's the PC# for this amp?

PC-3083-C.


I removed all the mosfets on that channel now other side one mosfet is pulling 6millivolts across rresistor.So the amp is still pulling current.

 

[Perry Babin]

See attached.

List which FETs are now out of the circuit and which FET has high current across it's 0.1 ohm resistor with the bias fully CCW.

 

[imraneesa]

See attached.

List which FETs are now out of the circuit and which FET has high current across it's 0.1 ohm resistor with the bias fully CCW.

Out of circuit fets
Q215 Q214 Q212 Q211

Q220 Q219 Q217 Q216


Current across 0.1 resistors

Q213. 5.7mV

Q218. 5.7mV


Q315. 1.2mV
Q314. 2.3mV

Q313. 1.0mg
Q312. 1.1mV
Q311. 1.2mV
Q320. 0.5mV

Q319. 4.1mV
Q318. 0.6mV
Q317. 0.8mV
Q316. 0.6mV

 

[Perry Babin]

Q319 or it's gate or source resistors appear defective.

 

[imraneesa]

Q319 or it's gate or source resistors appear defective.

I removed the fet. But the amp still trying to pull current. Other channel still showing 6.4mV across Q213 and Q218 source resistors.



After removing that fet causing high current across resistor and few more gets. I am having balanced current draw on left and right side fets. But the amp still trying to pull current

 

[Perry Babin]

How did the current change across the 300 series source resistors?

 

[imraneesa]

How did the current change across the 300 series source resistors?

I did not understand?

 

[Perry Babin]

What is it that you don't understand?

 

[imraneesa]

What is it that you don't understand?

What is 300 series

 

[caraudioguy2100]

He is asking what the voltage is now across the source resistor for the fet you pulled out (Q319)

The 300 series parts are marked on the board for example R301,R355 ect if you look at the silk screen printing on the board 1 channel all the resistors diodes ect are marked 3xx and the other channel are marked 2xx

 

[imraneesa]

What is it that you don't understand?

I dont see any current across resistors who's fets are out of board.

 

[imraneesa]

He is asking what the voltage is now across the source resistor for the fet you pulled out (Q319)

The 300 series parts are marked on the board for example R301,R355 ect if you look at the silk screen printing on the board 1 channel all the resistors diodes ect are marked 3xx and the other channel are marked 2xx

Thank you for explaining. I was so dumb lol

 

[Perry Babin]

You can't have current flowing through the resistors that have no FETs. You need to post the voltages for the resistors for the remaining FETs.

 

[imraneesa]

Q315. Out of board
Q314. Out of board

Q313. 1.7mV
Q312. 1.4mV
Q311. 1.6mV
Q320. Out of board

Q319. out of board
Q318. 1.6mV
Q317. 1.5mV
Q316. 1.7mV

 

[Perry Babin]

Are these the original FETs?

Is the other channel reading about the same?

Bias pots fully CCW still, correct?