Sundown SAZ3500D

[caraudioguy2100]

This amp uses FQA24N50 as the outputs .

Mouser shows stock but they are $5.39 each

Wondering if there is a good replacement for them that will work in this amp ?

 

[seankane]

I just repaired the output stage in one of these and it used IRFP360LCPBF.


The repair was a success and the amp is being driven hard and working great.


You will definitely have to replace the IRS21844SPBF on the driver card.


There is one driver for each side of the outputs. I replaced the one and one side of the outputs and it works great. If you have blown outputs the driver will be defective.


You will have to change all on both sides if you use these FET's. I think I purchased them for around $3.50 each if memory serves? I believe I used arrow or mouser.

 

[caraudioguy2100]

This amp is using 22 ohm Gate resistors with IRFP06N as the power supply fets .
I don’t have any 22 ohm on hand would 47 ohm gate resistors work ?

 

[caraudioguy2100]

Would anyone happen to know if 47 ohm gate resistors work in place of the 22 ohm gate resistors In this amp

 

[Perry Babin]

The 22 would be safe. The 47 would be borderline.

 

[caraudioguy2100]

Ok replaced the outputs and power supply fets .

Rebuilt the audio driverboard .

I’m getting -3.15 volts measured directly across the speaker terminals .

Any ideas where to start looking

 

[Perry Babin]

If you don't get any definitive answers, post a photo of the audio driver board.

 

[caraudioguy2100]

Here is a picture of the audio driverboard

 

[Perry Babin]

If you touch a speaker/dummy load across the speaker terminals, does the DC go to 0v or does the amp draw more idle current?

Is the relay engaging?

Have you confirmed that all power supplies going to the driver board are OK?

 

[caraudioguy2100]

I noticed it blew one of the IC’s again .

I replaced the IC and now when trying to power the amp up it it clicks on then straight into protection .

 

[Perry Babin]

Did any outputs fail?

Are you sure that the new IC survived installation? They often do not.

 

[caraudioguy2100]

No outputs failed they all test good .

I will have to check the driver Ic’s to see if they are still good

 

[caraudioguy2100]

The driver ic’s failed I’m guessing when installing them .

I have solder paste but at what temp do I set my soldering gun when using the solder paste since I don’t have a hot air rework station

 

[Perry Babin]

I never use hot-air to install ICs. You can use paste or regular solder.

Not all irons will be accurate. I think I set mine to about 600F. You want to get everything cleaned and prepared so that you just have to touch the terminals to get them soldered.

The following video is so bad that it may take down the entire internet. It was also before beta blockers so there is nothing good about it but it does show how quickly you can solder the terminals of an SMD IC.
YouTube

 

[caraudioguy2100]

I installed new ic’s again and used a lower temp and soldered them quick like in the video .

I get readings in the mega ohms besides 1

Readings from pin 5 to 7 for both ic’s read 6.61k

 

[Perry Babin]

5 and 7 are in parallel with 2 capacitors and the regulators (if the board is in the circuit).

You can desolder pin 7 and check the IC (5-7).

As a side note, someone else was reading about 6.6k from 5-7 for some unknown reason. If it's not the IC, it shouldn't be a problem.

 

[caraudioguy2100]

I have a brand new driverboard here and comparing readings from one to the other . I can’t use the new driverboard in this amp since it doesn’t belong to me and is for a different amp .

But so far everything is reading identical between the boards

 

[Perry Babin]

The ICs likely survived.

People swap driver boards but generally fail to check to see if the over-current threshold resistors match.

 

[caraudioguy2100]

Everything tests good on the driverboard .

I installed the driverboard and have the same issue .

When trying to power up it powers up for a sec then switches to protection

 

[Perry Babin]

Confirm that pin 2 is not directly connected between the two ICs. If not solder a bridge between pins 2 and 3. Does the amp still go into protect mode?