Rockford Fosgate T400-4

[rhempz01]

So I bought an amp for cheap and opened it nothing burnt and smells new, looks great. But has irfp064n for the power supply. All are shorted legs 1-2 in circuit. No power, is this a problem elsewhere besides the PS fets. And can I use the huf75344 in power supply

 

[Perry Babin]

It's likely that the driver transistors have failed. They're on the driver board.

I use the 064 when the rockford amps use the large transistors. The fairchild transistor should work as well.

The gate resistors sometimes fail as well.

 

[rhempz01]

So I changed the npn and pnp drivers for the PS, and now the amp draws 3.3amps of current and I shut it off. Failed output somewhere, none shorted. Any other ideas?

 

[Perry Babin]

Check the waveforms at the gates of the PS FETs with no B+.

 

[rhempz01]

Same 20v 5us perry?

 

[Perry Babin]

5v, 10us

Read the oscilloscope page of the site (page 73). Pay special attention to 'best initial settings'.

 

[rhempz01]

Looks a mess

 

[rhempz01]

I can't get anything from the gates on 5v 10us even magnified its very small

 

[Perry Babin]

Can you get a clean signal on pins 9 or 10 of the tl494?

 

[rhempz01]

There 5v on both of those pins. And Perry if you touch b+ without remote it draws current immeadatly don't know if that releavent or not.

 

[rhempz01]

Do you know the designation of the outputs originally for this amp. I'm wondering if they are in the correct order originally.

 

[Perry Babin]

If the center legs for the two outputs in each channel are directly connected, the P-channel output (leg 3) connects to the positive rail.