is there an earth for the cd player ?

[robster247]

Okay having some trouble with getting my 6x9's working through my amp. Everything is wired up correctly but when you turn to ignition on there is a red light comes up on the amp instead of the normal green light any ideas people ? Cheers

[stevo67]

Yes there is an earth mate & if no power was getting to the amp then you wouldn`t have a red light on.

[danny-vts]

re-do your earth cable for the amp, move it somewhere else or clean the connection up and sand the paintwork down to bare metal.
failing that...it could be a blown amp.

[robster247]

Okay will go through the whole lot tomorrow, hope its not the amp at fault as it was £400 :(

[danny-vts]

ouchhh

[devilsadvocate]

Okay will go through the whole lot tomorrow, hope its not the amp at fault as it was £400 :(

Most Saxo's are not worth more than £400 these days ;)

[robster247]

Haha nope they arnt, tried everything and it still doesn't work so will be getting thrown away.

[mechsman]

^ Send it to me (for a bit of postage money) instead of chucking it? Pretty please? What amp is it?

[robster247]

Theloudest.com 3000w

[mechsman]

Hmm, interesting. Is it a multi channel or is it their single channel class D (for driving subs)? Gussing it's a multi channel given you said you are driving 6x9's off it? Either way, could be fun stripping it down to find out what's gone pop. If you really are going to chuck it do you fancy posting it to me so I can strip it down to see which component has let the magic smoke out?

[robster247]

Will get some pics of the board as it has a lot of black aroung a coil thing, looks like its been hot :/

[mechsman]

Ah, that's not a good sign!

[robster247]

Think I have found what's up with it, just need a scap amp to take a tiny block off it

[mechsman]

Do what now? lol!

[robster247]

There are 8 little black chip things going into a coil of copper wire and it has snapped a connector off one of the little chips, what are these for ?

[mechsman]

Erm, not sure buddy. Would need to see pictures of the bit in question, or part numbers off it. Might be a mosfet or a voltage regulator from your description. When you say snapped a connection, does the connection look like it's been twisted/vibrated off, or has the chip actually blown off around the leg?

Still think you should send it to me instead of binning it though! lol! Would the manufacturer not accept a return as it's defective?

[robster247]

It is a mosfet irfz46n, and it looks like the heat has got the better of it and melted the casing, where can I find one of these ? Will there be one in a house cd player ? If I can't fix it then yeah I will send it to you :)

[mechsman]

Jesus! That mosfet is rated for 53 AMPS continuous drain! You've done well to melt that! Is there only the 1 in the line or is it paralleled with a couple of others?

RS components look to carry that model but they are out of stock until December. Is it in a TO-220 package? i.e. 3 legs + bolted down via a tab at the top?

[mechsman]

oh, and no I don't think you'd find one in a house hold cd player. It's only rated for 55 Volts, so it's a high current, low voltage style one, which is what you would want for a automotive application. House hold ones are more likely to be rated for higher voltage and lower current I would think.

[robster247]

Yeah that's correct, held down by a metal plate and has 3 legs coming off it yes.

There is a row of 4 on each side. Need one just to see if that's the problem haha

[mechsman]

Yup, sounds like the standard TO-220 package. That tab also acts as the heat sink, usually with thermal grease between it and the plate that it attaches too. It may well be that the grease dried out, that mosfet overheated and when it melted it shorted to ground. The amp controller has detected this and shut the amp down to avoid further damage. It's basically equivilant to shorting the speaker output wires.

You could try unsoldering the dead one, cleaning up the connections so it's no longer shorted and then carefully powering up the amp (on a limited current and voltage supply) with nothing connected to the outputs. If it clears the protection light you have the answer. It may not clear the fault though as the controller make still think there is an issue, or there may be something else at fault.

[robster247]

How the hell do you know about all this stuff haha, I have found them on ebay and for £1.80 its worth a go I have a soldiering iron etc so will get one ordered tonight and let you know what happens, thanks for your help mate

[mechsman]

I'm an engineer by training, lol! Not an electrical engineer admittedly (I'm mechanically bent) but power mosfets are used in most modern electronics where you need to drive any reasonable current, and can't make do with a relay (i.e. when you need to switch it on and off very fast repeatedly for years). TO-220 packages are pretty much standard for through hole components at this kind of power level.

The amp controller shutting down is pretty much common sense. Conceptually it basically goes like this: power up signal from head unit arrives, amp controller on, amp controller fires up the power stages in the amp and ramps up the output (this is why you sometimes get a pop when turning on an amp, it's the controller ramping the power stages a bit quickly), controller notices 1 ouput channel voltage is rising way too high/way to much, or is not rising at all compared to the other channels/set values in program (depends on the failure mode of the mosfet), controller continues to monitor the situation and decides that something is not correct, controller powers down or isolates (if it can) the output stages according to program parameters, controller may record this fact in memory if possible, controller lights the amp fault/protection mode light to inform user that something is kaput.

If the power is cycled the process will repeat or if the controller has a memory it may check if it was in protection mode last time and run a test to check if the fault still exists before attempting to power up the output stages.

[mechsman]

Oh btw, it looks like farnell have these in. Try here:

http://uk.farnell.com/jsp/search/browse.jsp;jsessionid=1B0WUHKNSBKIICQLCIRJKBQ?N=0&Ntk=gensearch&Ntt=irfz46n&Ntx=mode+matchallpartial&exposeLevel2Refinement=true&suggestions=false&ref=globalsearch&_requestid=259005

[robster247]

So that's what that noise is when I turn the key haha, I don't know a lot about electrics but I'm sure I can put a new one on, if that fails, I will pm you and if you cover postage, its yours haha. Will be coming out soon anyhow but if it works it should be worth a bit more but hey ho :)

[robster247]

Ordering now, thanks again mate

[mechsman]

Yup, pretty much. Older, high power amps used to be pretty bad for turn on "thump" which is basically the speaker cones being driven to one end or other of their travel. Amps nowadays (half decent ones anyway) ramp the voltage output relatively slowly to avoid this issue.

Lol fair enough chap. Let us know how you get on.

[mechsman]

One thing, make sure you get the thing the right way up when you put the new one in! lol! Personally i'd leave the old one in untill the new bit turns up so you can make sure it's exactly the same. I've seen it done where someone reversed the legs of a component due to the part looking similar from the front and back. Makes for unhappy controllers and normally lets the magic smoke out again! lol!

[robster247]

haha yeah ive left it as it was and will be living in the house untill it comes< you dont know anything about leds do you ??

[mechsman]

Gdgd. Erm, a little chap, what do you need to know?