Orion 1200 D

[mike49504]

Wondering if anyone knows what gate resistors are used in this amp?

When i recieved it they were missing I know the amp use's IRF3205's for the power supply fets but not sure what vlaue gate resistors it takes.


Any help would greatly be appericated

 

[Perry Babin]

22 ohms

 

[mike49504]

Thanks,

Next question is there is 1 resistor missing also that connects to the 3rd leg of 1 power supply fet do you know the value on that also?

 

[Perry Babin]

If it connects between the source and the trace that feeds all of the gate resistors, it's a 1k.

 

[mike49504]

Ok i replaced the power supply fets,gate resistors, the drivers.

I took out the 3 driver boards in the output section.

Amp still draws excessive current .


Wondering what i check next? since i cant seem to find anything defective

 

[mike49504]

With a current limiter in line amp will power up and produce clean audio.

But the problem im having is 4 of the power supply fets get red hot within a sec or 2 .

Wondering what i should check at this point?

 

[Perry Babin]

Does the gate signal look identical for all of the FETs?

 

[mike49504]

.5 volts div 10us ??

 

[Perry Babin]

That's a good starting point. Adjust the timebase to get 3-4 complete cycles displayed.

 

[mike49504]

Heres what i get off the gate legs for the power supply fets . They all look this way

 

[Perry Babin]

That doesn't look good. What drivers did you use?

 

[mike49504]

The drivers are C3198 Theres 2 of them on the driver board . on 1 of them the middle leg connects to the gate leg of the fet and the 3rd leg connects to the 3rd leg of the fet. The other
C3198 the first leg connects to the 3rd leg of the fet .

The on the main board a C3198's first leg connects to the 3rd leg of the fet And the 3rd leg of an A1266 connects to the 3rd leg of the fet.

If that makes any sense to you

 

[Perry Babin]

Post a photo of the power supply driver board.

 

[mike49504]

I took it out of the amp so i could get a better pic.

 

[Perry Babin]

Both of those are supposed to be a1266s.

email me.
babin_perry@yahoo.com

 

[mike49504]

I replaced them both with A1266's and it still doesnt look good Heres what i have now

 

[Perry Babin]

What does the waveform on pins 9 and 10 of the 494 look like?

 

[mike49504]

First pic is pin 9 second pic is pin 10

 

[Perry Babin]

Are the 220 ohm resistors on the driver board within tolerance?

 

[mike49504]

Yes both test 220.9 ohms