I need the service manual of main amp. powered subwoofer prx618s

Q3; means transistor number-3. Refers the part number by its service manual. Gopakumar Gopalan Google

Isolate and look for possible shorted components.

Isolate the main power transformer from the board, and see if the

fuse still blow.

If it doesnt , then the rectifier and capacitors to the regulators.

But don't forget to check for possible shorted transistor

Yes this generally means a major problem - main transformer or output transistor(s) likely.

One year factory warranty on the electronics.

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Suspect an overload in either the power supply or main amp section. Chances are some kind of semi-conductor has gone gone short circuit. You might be able to spot it with either a crack or damage or signs of burning. If it is a transistor an Ohm Meter will show it up, as it will be just like you had touched the probes together, when touching two terminals with them.

Most of the time it's 2 things, first thing is a section on the PCB has burned out and this leave you with very little power going to your speaker, This is common by using incorrect wiring or peaking the amp all the time, You can start by pulling the PCB out and looking for any physical damage, If there is some you can solder a connection with copper wire. The second thing is blowing your finals, This happens when one side of the bridge for the PNP NPN transistor section blows out usually on the on position and this can send a dead short to your other final transistor. they will be in pairs of usually starting with A,B,C,D and a number grouping. This is next to impossible to fix.

The reason a fuse blows is due to some semi-conductor device now acting like it was a piece of wire. The thing could be either in the power supply part or the main amp device. If you see something like a transistor or IC that's been getting hot or is damaged that will be the culprit. If all OK, If I was you, I would replace first the main part for the amp section. It might be the biggest or on a heatsink.

Any fuse blowing is caused by an overload in either the power section or the amp part. Look arond for burnt or damaged parts first. It could be caused by a shorted transistor, but your best bet is to follow the circuit from the fuse on the PC board.

Hi again! Been thinking about this and you might not need to wait for someone to answer. I assume the transistor in question has blown apart or burnt up so you can't read the number?
However does it come off the heatsink as part of the main amp? If it does then it might have a brother around it. For if it is say the left or right channel transistor, then the other channel will have the same type transistor. Remember the left and right channels are copies of one another. If you see 4 transistors on the heat sink then it's a push-pull amp. They work in pairs, one pair for each channel. By the way it's best to replace the pair, even if only one is blown.
If on the other hand the blown transistor is from the power supply section, then you will have to wait for someone to help, or get the service manual.

You have an overload in the power supply or main amp of the subwoofer, often caused by short circuited transistor. Check this out by putting an ohm meter probe to each of it's legs. If it acts like you were touching the probes together you have found a guilty part.

What probably happened was both of the final audio output transistors shorted. This caused a higher than normal drain on the switching transistors on the primary side of the torrid power transformer causing one to short and then blowing the fuse. I replaced both switching transistors and ramped up the current to about 5 amps. I could see the power supply was not working but there was still a short. I traced the short to both audio output transistors. Replaced them and unit is like new. After I found a service manual on this item it was a breeze to find the problem.