Fusion NV AM25001

[mike49504]

Im working on this amp it does some strange stuff.

If you power the amp up it will play fine until it warms up a lil bit then it sends straight dc voltage out to the sub (29.69 volts) And a cap ticks also its a big cap like the fosgates have in them the red ones

Wondering what this might be

[Perry Babin]

If it's actually heat causing the fault, use a blow dryer or a heat gun to heat various components. Go slowly because the lag between hitting it with the heat and it showing the fault could easily be 10-15 seconds. When you get the general area narrowed down, use your soldering iron to heat each individual component.

[mike49504]

Ok the other crazy thing is the amp works until it gets hot but wondering if u seen one of theese boards?

Looks to me like there were burnt traces at one time and there is a crap load of 47 ohm resistors jumped all over the board in the output section

So wondering if that factory or someones cobble job

I left it alone since the amp plays until it gets warm

Also they are using lm318n for the op amps and 1 of them shows 20.86 volts on pin 8 of it wondering if this may be the problem

[mike49504]

Ok I check this op amp out when its cold and on pin 8 its -4.37 then it warms up a lil and boom 29.68 volts on pin 8 .

And 29.68 on the outputs

[Perry Babin]

The only fusion amp that I can remember seeing was an AM15001.

20.8v with what as the reference? Use the RCA shield as the reference (black probe).

What's on pin 4?

Are these in the audio or in the power supply section?

[mike49504]

pin 4 has - 4.09 pin 8 went to test it the amp made a wine and blew the fmg22r

[Perry Babin]

It could have had ±12v that was shifted up 8v. This could be due to an intermittently shorted power transformer.

Does the rectifier read shorted or open out of the board?

[mike49504]

Its not thoose its one of the 640's that blew

[mike49504]

ok on this amp i am an idiot i pulled the diodes off the board awhile back they are in line with the fets and misplaced them wondering how do i tell which one goes where for the pos and neg also dont remember what they were using in this amp could i use a 1620 and 1620 r?

[Perry Babin]

The 1620CT center leg would go to the positive terminal of one of the rail caps.

The 1620CTR center leg would go to the negative terminal of one of the rail caps.