Power Acoustik A2400db

spooney

Member
2006-12-01 4:41 am
Just received this amp in a trade.It blows fuses at turn on but it doesn't appear to have toasted output fets.I did notice that an inductor directly next to one of the transformers and near what I believe to be the rectifiers has some charred windings that look to be the result of it coming in contact with the bottom plate of the amp.There is green and copper colored windings on this inductor that appear to be shorted together.Is this possibly causing the turn on issue? Also one of the inductors near the speaker outputs has one strand of wire that appears to have been burned but other than that it looks fine although it isn't mounted very securely to the board.It just kind of bounces around.I snapped a couple pics of the problem areas that can be seen here : http://www.putfile.com/album/177422
 

spooney

Member
2006-12-01 4:41 am
it doesn't pull current until the remote turn on signal is applied.It turns on for a split second,the fans starts to run and then poof goes the fuse.I was just poking around on it and I noticed one of the rectifiers was completely broken off of its leads at the board.
 
usually you can take the rectifiers out off the board , that seperates the music amplifier from the power supply section. If you try to turn the amp on and it stays on without pulling high currents you ´ll find the fault past the rectifiers in the music amplifier section.

For your testing insert a very small fuse (5A max ) or a 2Ohm resistor (some high wattage 20W or more) in series to the 12V power line. That way you will keep the amplifier from going up in smoke.
 
Shorted inductors are a VERY common problem on these amps (and all of the various clones).

You'll need to repair the inductors before you can do further testing. The common mode chokes (green and yellow) generally short where the terminal winding goes over the top of the other windings. They also short at the bottom where the terminal windings turn 90° to go into the board.

If one strand of the inductor is burned, you should rewind it if the amp is going to be sold or if it belongs to someone else. If it's yours and you don't want to rewind it, the amplifier will work normally with only one broken strand.

The output inductors generally short where the 'inside' terminal winding goes over the inside edge of the windings. These rarely burn open and insulating the windings will solve the problem. Both of the output inductors tend to short in the same way so you need to insulate both of them at the same point. If yours has shorted at a different point, you still need to insulate them as described. It's a weak point and virtually all of them will short.

If you pull any of the inductors, they will be difficult to get back into the board because the windings are cut flush with the bottom of the board. Try to insulate them without removing them.

Use a current limiter (as was previously suggested) when doing initial testing. After you believe that you've repaired all of the problems with the inductors, twist and otherwise apply pressure to the windings to insure that there are no other shorts or weak points in the insulation.
 
Power acoustic may sell the parts. They are one of the few of the clone 'manufacturers' that are willing to offer support.

If you can buy the inductors, you need to insulate the weak points before installing them.

When you call them, ask if the parts are new (with long leads) or 'pulls' from other boards. If they aren't new with long leads, you may as well use what you have (rewind them).

There's a good chance that the new inductors will have a single large strand instead of the litz wire of the originals. If that's the case, the hole in the board will be significantly lartger than the wire. To make the connection reliable, scrape the solder mask from the bottom of the board and bend the wire so it lays down on the board. This will help relieve the stress on the solder connection and will provide more surface area for soldering.

When testing the amp, check the fan. It should turn freely and should operate quietly. If it whines when running or turns slowly, it needs to be lubricated. If it fails due to poor/dry lubricants, the amp may fail.
 
I have one of these and I seperated the windings on the core far enough where they weren't touching and epoxied them. The amp works aok now. The core actually got so hot it de soldered itself from the board.:bigeyes:


I've tried to call the guy several times and I'm going to keep it for a few more months. If he doesn't call back... guess where its going.:D
 

spooney

Member
2006-12-01 4:41 am
when insulating the common mode choke does every individual strand need to be insulated form each other or just the green from the yellow?I know my pics don't really show it but this thing is burnt pretty good and I don't really see a possible way to isolate all the windings from each other.
 
I ´d suggest you get coated copper wire and rewind the whole thing. It´s not as hard as it seems (thumbs up). While spooling the old wire off the core count the windings and write them down . Hopefully the core itself is ok.

I had an old Altai amp years ago where the core was split into 2 pieces.
 
Each twisted bundle of wires acts like a single, larger wire. The wires of the same color in a bundle can contact the others in the bundle but only at the same point in the length of the bundle. They can NOT make contact with the next turn/wrap around the core even though they are essentially the same wire.

The yellows cannot contact the greens at any point.

Did you check with PA to see if they would sell the inductors?
 
Measure the individual strands (with a dial caliper) to determine the proper gauge. Make a bundle of wires with the same number of strands and re-wrap the core precisely as it is now. If the winding starts at the bottom and goes into the center of the core, that's how it has to be wound when you re-wrap it.

When you pull the old wire off, you can use that to estimate the length of wire needed. Cut the new wires to at least 6 inches longer than the original wires to make sure you have enough.

When you buy the wire, you'll probably have a choice of solder-strippable or high temp insulation. Solder-strippable insulation burns off as you apply heat with a soldering iron. High temp insulation is more durable but you have to scrape the insulation off of the wire which can be very time consuming.

When you reinstall it, apply an adhesive like Goop or E6000 to the point where the insulation wore through on the windings. Also apply a bit of adhesive (between the wire and the core) at the point where the windings leave the core and go into the board. This will hold the core and prevent damage in the future.
 

jol50

Member
2007-11-08 2:14 am
I have a clone that pops the inductors in the outputs. They did not short just come out of the board and start to unwind. I put zipties on them and when back on board I goop them down and goop the zipties too. They seem to work ok. I put extra solder on the ends, they don't have much on them. I think this is from vibration more than anything, and I have seen where they don't have them tight against the board to start with. I get done and have to cut them off the back side.