Reversed polarity on soundstream lil wonder 4 series amplifier

[shandev]

Good day i need help in repairing my amp I have the amplifier out of the car and connected it direct to a 12v battery, i also don't use a head unit so i bridge the +ve terminal and the remote wire for the amp to turn on, but one day i accidently reversed the polarity while connecting it to the battery and it wont turn on no lights so i opened it up and saw the on board fuse connection break it is not a pull out fuse its like a strip on the board so i solder it back in place the amp still don't turn on the wire on the battery just sparks when i connect it meaning its getting current now like it always do when i use the amp but it still wont turn on, so i don't know if when i connected it wrong the remove wire received the negative voltage and that damaged some start up ic on the board also i haven't checked the diodes i don't have a multimeter and there are mostly zener dioes in the input power side of the board so can all tell me it the ground to the remote that was bridged to positive on the amp cause some ic problem thanks you and sorry for bad engilsh.

[nevetslab]

I think you're in over your head technically with this one. Having reversed the battery connections to this amp, and you're getting sparks, the front end of the switching power supply is damaged. Whether you can get it repaired by local techs qualified to do this for less than what it would cost to replace it outright....you'll have to assess that, or take their word on their findings. Good luck

[Jazz P Bass]

By 'reversing the polarity voltage' you more than likely fried the amplifier.
These car amplifiers are very complicated.
- First the power supply circuitry:
They take the +12Vdc from the car battery and bump it up to 70-100 Vdc.
- From there it's basically a standard amplifer.
Without the skills or the tools, more than likely you will not succeed in repairing the unit.

[shandev]

thanks you all i appreciate it, i will buy a dmm and check to see if its the reverse protection diode that shorted because the amp looks fine no blown caps or resistors nothing seems like the protection circuit did its wor i will let uall know how it goes again thank uall

[shandev]

i cant seem to find to find a schematic for the amp tho soundtream don't have any online

[Enzo]

CAr stereo is a whole differnt world from what we usually service. But you get my same advice: do not rely on what you find on a web site, contact them directly and ask specifically.

[Jon Snell]

It will look something like this;

I suspect the main damage is on the primary of the power supply with IC201 and Q201 possible failures.
Probably more cost efficient to purchase a new amplifier.

[Jazz P Bass]

If you feel up to it, here is a shot of the LW II.
The components on the left are the power supply. Check the parts that are bolted down to the chassis for shorts (ie: very low resistance).
The components on the right side are the power amplifier circuitry.
Same thing. Check the bolted down parts for shorts.

I got a chuckle out of there spec sheet:

[Jazz P Bass]

This chap (Barevids) has a really good understanding of car audio.
In this video he attempts to explain how they work:
Amplifier repair - How do car amps work?? Part 1 - YouTube
Enjoy.

[drewl]

I've repaired a few over the years.
doesn't it have any input power protection?

[The Dude]

I'd bet on something like D202 in the drawing uploaded by Jon in post #7. If the OP is lucky, a shorted diode might be the only problem.

[shandev]

If you feel up to it, here is a shot of the LW II.
The components on the left are the power supply. Check the parts that are bolted down to the chassis for shorts (ie: very low resistance).
The components on the right side are the power amplifier circuitry.
Same thing. Check the bolted down parts for shorts.

I got a chuckle out of there spec sheet:

thank you so much i will check it out with a multimeter, also this amplifier dosent have those biger diodes that run foward bias to the positive strip on the board from the negative (as in the reverse polarity diode) i dont see any only very tiny orange is colored zener diodes so iam thinking it could be the power supply transistors and the driver circuitary will need to be checked

[Jazz P Bass]

Can you post some pics?

[shandev]

I've repaired a few over the years.
doesn't it have any input power protection?

look like it failed cause after soldering back the fuse its not working I will need to check the resistance on the input transissters and driver an see

[shandev]

Can you post some pics?

sure