Repairing blown up D'artagnan 5.1 channel amp

Alright guys, I come to you requesting help. I have a soundstream D'artagnan 5.1 amp. Its the older silver model.

I was running WAY too low of an impedance, not realizing my woofers in my doors were 1ohm. After running it this way for almost a year, I toasted a channel in the amp.

Its very obvious which channel it was, all the bias resistors (that is the name for the big 3w resistors right?) are burnt in half. Those resistors and outputs are toasted.

Now, I removed the output devices and burnt resistors in an effort to get other channels working. No sound output from the other channels. It is not blowing 15 amp fuses like it was before I removed the outputs and resistors.

What else got damaged? I looked online for a service manual with NO luck. I can get photos as well. I do have some experience (little) successfully repairing home audio gear, but this just looks alot different!

Thanks for looking everyone, I would really like to have this unit back working again! I miss it dearly. No, I won't run a super low impedance on it!

Evan

EDIT; I have not actually worked on this amp in over a year. Just dug it out.

One of the coils on the power supply is getting HOT when the amp is on. I also had to replace the two caps in the photo that were destroyed as well. I assume that was from taxing the power supply too much.
 
Here are a couple pictures.

Thanks Everyone!

[IMGDEAD]https://i230.photobucket.com/albums/ee225/240z4u/Soundstream003.jpg[/IMGDEAD]

[IMGDEAD]https://i230.photobucket.com/albums/ee225/240z4u/Soundstream002.jpg[/IMGDEAD]

[IMGDEAD]https://i230.photobucket.com/albums/ee225/240z4u/Soundstream001.jpg[/IMGDEAD]
 

Perry Babin

Member
Paid Member
2003-11-20 11:01 am
Louisiana
www.bcae1.com
You can get the schematic diagram for the amp.

Are the 49.9 ohm resistors open on the driver board for the blown channel? If so, the driver transistors may be damaged. The driver transistors should be checked even if the resistors are intact.

The amp should power up if you have pulled the defective output transistors.

Is there any DC on the speaker output terminals of the blown channel (or any other channels)?

Are you getting both positive and negative rail voltage to the other output transistors?

Are you getting positive and negative regulated voltage on the op-amps in the audio section?
 
Before I had not fully removed the outputs, just the bias resistors. I pulled bias resistors and the dead outputs. Now the power supply isn't getting abnormally warm. Although two of the large resistors in the power supply are getting much warmer then the rest.

Rail voltage was taken from the test points in the upper left hand part of the board in the first photo I posted above. Rail 50vdc.

.005 vdc on the outputs. Its the same on every channel (except the channel with no outputs). That one has .3v on it.

Evan

BTW, I do have a transistor tester. So I can check the drivers.
 
Okay, I figured it wasn't coincedence that 15+15 was basically 30.

WE HAVE AUDIO!

Dude, I am stoked. I am going to reassemble it without the 5th channel. I never used it and need this amp for my fiance's car.

Thanks so much man! I can't thank you enough.

Evan

EDIT; I am placing an order to mouser anyway so Ill get outputs and drivers. Might as well fix it while its apart!
 
If you have to pull the drivers, look at the ends of the legs on the transistors. If there are burrs on them, cut them with a sharp pair of flush cutting pliers to remove the burrs. Apply additional solder to the legs and lay your iron across all 3 legs (so the solder will melt on all of them at the same time). Then pull the transistor. Don't try to desolder each individual leg. You're likely to damage the board. If you don't have any flush cutters, buy a pair of Xcelite 170M cutters.

Mouser probably won't have the 2SA1381 and 2SC2503 driver transistors. You can get them from MCM Electronics.

Also check the 1.3k and 1.33k ohm resistors on the driver board. I've seen those fail also.