Audio Gods AG 7000.1D

[chrisg4]

hi all,

i have the this amplifier, it is protection. I tested all the psu fets and output fets, all test good. when i remove the driver board the amp comes out of protection. I replaced the driver transistors (Q5, Q6, Q9, Q12) but it is still in protection. It also comes out of protection when i remove the inductor.

driver board

An externally hosted image should be here but it was not working when we last tested it.

 

[Perry Babin]

On similar boards, Q7 and Q11 have a high failure rate. Also check all of the 470 ohm resistors in that area.

 

[chrisg4]

Hi Perry,

will check those:

more pics

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[chrisg4]

On similar boards, Q7 and Q11 have a high failure rate. Also check all of the 470 ohm resistors in that area.

Hi Perry,

i have replaced Q7, Q11, all the 470ohm resistors are good. amp still goes into protect...

also checked the 100k pulldown resistors, quite a few of them measure 25k...

 

[Perry Babin]

Shouldn't the pulldown resistors read 100k/6 (6 outputs per side) if all of the gate resistors are within tolerance?

Is that last photo the current state of the amplifier?

 

[chrisg4]

Somehow one of the driver transistors died, i replaced it. Still went it protect but after a while its working.

 

[chrisg4]

The amp is in protect, i noticed a zener diode missing - ZD02

An externally hosted image should be here but it was not working when we last tested it.

 

[Perry Babin]

Does the 4.7v(?) next to it mean anything?

Are you sure that it was installed, originally?

 

[chrisg4]

didnt even notice that...

yes, looks like it was cut out on top of the board, the legs were still there.

 

[chrisg4]

Hi Perry,

I finally got a scope, I didn't replace the zener diode yet.

On the high side (irf9640) the voltage on the Gate and Source are not equal, there's no voltage on the drain, is this correct?

On the low side, the gate and source have the same voltage. nothing on drain.

 

[Perry Babin]

Are the outputs in the circuit?

The source legs are connected to the rails.

The drains won't have any DC. They drive the output inductor which drives the speakers.

The gates (when the amp is functioning normally) will have a 10v amplitude drive signal that drives from the rail, 10v towards ground.

 

[chrisg4]

no, the outputs are out of the circuit. when they are in circuit the amp goes into protection.

 

[Perry Babin]

Drive a strong 50-100Hz signal into the amp. Do you see a 10v square wave on all output transistor gate pads?

 

[chrisg4]

Hi

this is on gate pads

An externally hosted image should be here but it was not working when we last tested it.

 

[Perry Babin]

Unless you tell me the scope settings or post a photo sharp enough to read all of them off of your scope (including 1 or 10x probe setting), that doesn't tell me anything useful.

 

[chrisg4]

probe is set to 1x

pics:

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

An externally hosted image should be here but it was not working when we last tested it.

 

[chrisg4]

this waveform is on the gatepads regardless of the input 100hz sine wave

 

[Perry Babin]

That just looks like noise. Is it the same frequency as you find on the PS FET gates?

 

[chrisg4]

probe on 10x

Gate drive:

An externally hosted image should be here but it was not working when we last tested it.

Drain:

An externally hosted image should be here but it was not working when we last tested it.

 

[Perry Babin]

The gate pads for the outputs should have a similar signal but at 100Hz when you drive a strong 100Hz signal into the amp and driving from the upper and lower rails, not from ground.