Rockford Fosgate 800a2

[mike49504]

Ok sorry

The 9640's have 0 volts

The 640's have 3.37 volts

The 28 volts is positvie voltage i triple checked that my meter probe was on the right + output terminal

 

[Perry Babin]

If the 640s are 'on' (the 9640s are off with 0v gate voltage) the voltage should have been negative. There is a conflict here.

Why the right positive instead of the left negative (left channel is defective) or the ground terminal?

 

[mike49504]

Sorry my mistake Its been the right channel all this time thats defective..

with black probe on ground terminal and red probe on the right channels - terminal i get -28 volts

 

[Perry Babin]

The parts I told you to remove were in the left channel.

You need to remove the corresponding parts in the same order doing the same checks as were suggested earlier.

 

[mike49504]

I lifted D302 and D305 nothing changed

Then i lifted Q306 and Q307 voltage dropped to 2.53 volts

 

[Perry Babin]

Voltage where? Remember, you need to be specific.

 

[mike49504]

The voltage dropped from -28 volts down to 2.56 volts on the right channel outputs

 

[Perry Babin]

Positive 2.56v?

Are the outputs in or out of the circuit?

 

[mike49504]

Outputs are in circuit..

Black meter probe on amps ground terminal Red probe on left channels negative terminal I get -2.5 volts on the output

 

[Perry Babin]

Left negative?

 

[mike49504]

No left negative

 

[Perry Babin]

There's either something wrong with the meter or you have a broken ground in the amp. The left negative and the right positive are connected directly to the primary ground.

 

[mike49504]

Ok im a lil tired sorry now i got mt dew in me i can think again...


If i place the red probe on the right channels + terminal and

the black probe on the right channels - terminal i get 2.08 volts


The left channel is fine in this amp

 

[Perry Babin]

That means the DC voltage is -2.8v.

Post the DC voltage on the outputs again (gate to source, black probe on source).

If you connect a speaker across the speaker terminals does the current draw increase any?

Check the two transistors that are out of this channel. Do either appear to be defective?

 

[mike49504]

The transistors test fine..

On all 9640's and 640's from gate to souurce i get 0 volts now..

I still have the - 2.68 volts on the channel

If i connect a speaker to that channel the current draw remains the same.. it doesnt increase

 

[Perry Babin]

Did you check Q306 and Q307 after removing them?

 

[mike49504]

Ok im gonna put this amp on hold for now Since the guy called today and said he wont have money for atleast 6 months to pay for the repair So im gonna put it aside for now and work on the other ones i have here..

 

[megael9]

fogate power 1000.2

this amp have 35v at one of the speaker terminal, no shorted
output or drivers. voltage at the tl072 pin 8 is +14 volts
and pin 4 +6 volts instead of -14. any suggestion?

 

[seankane]

I am a little confused on which channel has the problem after reading this post. If the left channel is the problem.....................

Check R262,R263,R234,R235, and see if they are within tolerance. If they are they should read at or close to 20 ohms. If these resistors are out of tolerance they can produce a generous amount of DC on the channel.

 

[seankane]

this amp have 35v at one of the speaker terminal, no shorted
output or drivers. voltage at the tl072 pin 8 is +14 volts
and pin 4 +6 volts instead of -14. any suggestion?

Megael9 check the LM337 negative voltage regulator and see what it reads for pins 1,2, and 3.