hifonics hifi1000.1d

[Hexhclass]

This amp came in with two shorted output and some leaky PS FETs
I replace all PS FETs and remove the shorted output.Amp has + - 21.23
on the center leg of the rectifiers is that normal?Rail caps are rated for 60v.The out puts are IRF640n can i used irf540n or any other fet for test?

 

[brandes.cm]

I have use Fairchild FQP19N20 in Rockford amps, not sure if the hifonics would like it or not.

The IRF540N is only rated at 100V, not 200 like the IRF640N.

 

[timwebb]

If u use them I wouldn't use a heavy load. I always change the drive transistors when I change the output transistors.

 

[Hexhclass]

Do i need to change all to 540 or i can just mix it with the 640

so the 21.23v on the rectifiers is high enouth?

 

[timwebb]

i wouldn't mix them. the voltages are different. i think it would be safe to use all 540's. for 1000w amp 21v sounds about right

 

[Perry Babin]

Can you post a photo of the inside of the amp?

 

[Hexhclass]

hifi

 

[Perry Babin]

Are you sure that the power supply is working properly? I would expect more rail voltage for this amp.

Do you get a different rail voltage is you place the black probe on the negative speaker terminal?

 

[Hexhclass]

Same voltage with black probe on negative speaker terminal.

I think the power supply has a fault.I remove the rectifiers and the AC voltage coming to the pads is plusing up to about 53v.The power supply fets getting hot

fets
1:2.76
2:10.1
3:0.00

 

[Perry Babin]

Does your meter generally read approximately 5v DC on the gates for an amp without a regulated power supply (or in an amp without the PS FETs in the circuit)?

 

[Hexhclass]

yes,about 4 to 5vdc with fets out of the circuit

How can i no if the power supply is regulated?

I mostly work on chinese and korea made amps

 

[Perry Babin]

yes,about 4 to 5vdc with fets out of the circuit

**** Is that for this amp of for other amps?

It's difficult to tell if an amp is regulated or if a fault is causing the rail voltage to be lower than it should be.

 

[Hexhclass]

4 to 5v for other amps

This amp has 2.76

I removed half of the output Q204 Q214 and Q215.Rail voltage went up to 37.6v
I check all 4 output drivers out of the board and tested good.

PS FETS still getting hot out of the sink even when i pull both rectifiers

 

[Hexhclass]

I think i had a solder bridge on the output section.ALL outputs in circuit
I install two new rectifers rail voltage is - + 37.6v.

Amp has good audio but PS FETS still getting hot out of the sink.I put the board back
in the sink and run it for about 20min with 500w 4ohm speaker.It seems to be ok
but am just wondering how hot should PS fets get for class d amps get out of the sink?

 

[brandes.cm]

They will get hot, the package can only shed so much heat on its own.

sent from an IRFZ48N

 

[Perry Babin]

If they get too hot to touch within a couple of minutes at idle, there is likely a problem with the driver circuit. If they don't get that hot that quickly, it may be OK.

 

[Hexhclass]

The Fets get to hot to touch in less than a minute.I test all four driver transistor out of the board and they tested good.This amp has a little board in the power supply with the pwm IC on it .THe number on it is scratch out but i can see it has about two 00 on it can that IC caused that problem?

 

[timwebb]

u checked the drive transistors?

 

[Perry Babin]

Do you have a scope?

Post a photo of the component side of the driver board.

 

[Hexhclass]

yes