JBL GTO 1201.1 Problem

[Perry Babin]

If you remove it, does the amp stay in protect mode?

Have all transistors tightly clamped and have a current limiter or a 15 amp fuse in the B+ line when you apply power to the amp with that transistor out of the circuit.

 

[bigpun4fubu]

q401 right?

 

[Perry Babin]

Yes

 

[bigpun4fubu]

still in protect with Q401 removed

 

[bigpun4fubu]

the protect light is extremely dim

 

[bigpun4fubu]

it has a red dot in the lens you can only see it up close , so just my glancing it looks as if the protect light isnt on , im guessing it took a lil bit to charge the caps

 

[Perry Babin]

Post the voltage on the pins of Q403 again.

 

[bigpun4fubu]

Q403 pin1 11.03v pin2 -.445v pin3 10.7v

 

[Perry Babin]

Remove Q403 and check it carefully (confirm that it has two good junctions and there is no leakage).

 

[bigpun4fubu]

The OHMS readings were steadily but slowly climbing

 

[Perry Babin]

That looks OK. Is the LED still slightly lit?

 

[bigpun4fubu]

ill check

 

[bigpun4fubu]

protect led is now completely off

 

[Perry Babin]

Reinstall Q401 and Q403. Confirm that the LED is again slightly lit.

Remove (or desolder and lift one lead) of R415. Does that prevent the LED from lighting up?

 

[bigpun4fubu]

protect lit with Q401 and Q403 installed..... Protect Led completely off with R415 leg disconnected

 

[Perry Babin]

Carefully check D404 for leakage. With R415 out of the circuit, you should be able to check it in the circuit.

 

[bigpun4fubu]

D404 diode check .545 do i need to power it up and check voltage across it with red probe on side with black stripe?

 

[Perry Babin]

Check it on resistance. Check it with the probes one way then reverse them.

 

[bigpun4fubu]

D404 .8m ohms black probe on black stripe, reads OL with red probe on black stripe

 

[Perry Babin]

That looks OK but it appears to have been leaking in the circuit. Do you have any diodes on hand?