Kicker ZX750.1 Green Light No Output

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This is an older 06/07 model ZX
This is my first amp repair and I've done a lot of research and have most of all the tools needed new ones on the way.

Thing is about this amp is I can not find a schematic anywhere online.
So I looked up many amp problems and 90% is caused by a bad mosfet

I found two mosfets that seem to be a little darker at the base like possibly somewhat burned and seem to go with this. But if these where bad wouldn't they kick my amp into protect?
But they are on the output side of the amp

Also if I replace these I know I have to replace all those that go with it... Again no schematic so would I just replace all or would all that are that mosfet type be good enough. I have a few pictures and videos I could possibly post up for you guys to look at if you like I just don't have a good multimeter to test them and I am waiting on mine to get here.
 
If you measure the resistance between drain and source then a faulty mosfet is usually shorted. Rarely I have found a short between gate and source.

I have designed a few irs2092 based maps and when it fails it usually takes out the 2092 with the mosfets so I always now change both just in case. It seems a shame to risk new mosfets with a possibly faulty 2092.
 
So you think it may be the amp as a whole?
I never used this amp very hard it was turned quite a ways up but always ran at 4Ohms while I used it. When it stopped working it didn't pop or crack, I turned car on and just nothing. turned off tried again worked and that was the last time. after I turned car off the amp never made sound after that. still powers on and off as should and doesn't go into protect. I put in a new amp in its place and everything works flawlessly and my new amp sound more crisp (not loud) than this lovely kicker which dumbfounded me at first.

It is again a old amp and I have pictures but what would I need to test and how would I go about it.

Again my first amp repair and I am just trying to learn, I never did electronics just computers and cars. Expanding a little more now lol

What setting on my multi will I need to use to test MOSFETs correctly, and to see if it's possibly another problem.

Thank you for the advice
 
Also want to get these ordered and if I'm right the output ones are the cheaper ones but again no schematic and just guessing from looking inside of the amp.

Are the Output Mosfets the
IRF640 and IRF9640
and is it possible that I can just replace these or do I need to replace all 22 Mosfets?

There is no where around my BFE area that sells these or knows what I'm talking about so I'm getting them online and most are across seas + they are cheaper.
But if just needing these its like $10 but if needing al its more like $50
 
I have worked on many of these amps and can walk you through the repair if you like.If the relay clicks after a short delay upon turn on the relay contacts may be corroded and not outputing to the speaker terminals.If you do not hear the relay click the relay is not getting its turn on voltage from the soft start circuit,which could be a number of things, such as an open via, a break in the trace that runs from the power supply to relay, a bad switch transistor or a bad soft start.If and when you replace all 10 of the output mosfets, make sure that the resistance (with the power turned off of course) between the outside lead(Gate to Source) of each output approx 50 Kohms for the IRF640's and 33 Kohms for the IRF9640's and that the 10 ohm(?) gate resistors are in value and connected to the gates. If this checks out( you can do this check prior to soldering the mosfets in place). Once you have the board back in the chassis, and the pressure bars tight (you can use a power driver, but be careful not to crack the FETS or other devices, I prefer a hand driver myself). Do you have a scope? If so, there are some test points to see if you have drive from the LM361(heart of the class D amp) to the output mosfets. If you don't have a scope, you can use your VOM or DVM and check the voltage across the output FET's, same as the resistance Gate to Source. The voltages 4.5 volts DC on the 640's and around 4 volts on the 9640's. If this is what you find the the basic operation is of the amp is good and if you still don't have output check the relay as I stated above.
 
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To save sets of output transistors I always remove them (or disconnect them) and loop back the output of the driver back into the LTP.
I can then power up with very little chance of a short across the power supply.
I then check for DC on output. If that is OK I apply a sine wave and check the output.
I also check bias voltage after resetting it to zero volts.
Only when I am happy with that do I even consider fitting output transistors.

This technique has worked well for me over the years.
Just repaired a 1980 Maplin amplifier module that way. Turned out to have a bad transistor plastic insulator which was cheap to fix.
 
One more thing, If you have a scope it will be easy to determine whether the relay is bad. Assuming the amp is working and the amp is passing audio, you will see audio on the input and the output of the relay. If you can post a pic or two, I can point to some test points to look at. Let me know if you have any questions.
 
What do you mean a Scope, like I said I'm still new to this stuff. I have a MMS that will be here in a couple of days. What are you wanting pictures of and I can have those uploaded. Testing fets are just set to Ohm resistance and place onto leg 2 and 3 correct?

What other things are possible to test with my MMS and what do you think I should test before I actually start replace parts on the board?

Thank You all for your time to help me on this. Most parts I order are from over seas and take time to get here but are cheaper.
 
A oscilloscope is like a voltmeter, but with a time aspect to it. It can show voltage over time in a graph (voltage axis + time axis). It makes it a lot easier to repair amplifiers and other electronics because you can SEE how the voltage is changing over time, unfortunately most scopes are expensive.

An externally hosted image should be here but it was not working when we last tested it.



Don't just replace the mosfets and power it back on. Failing transistor amps have the nasty habit to create an 'avalanche' of failing components. You might be lucky, but you will have to check the other parts too to be sure nothing else is broken.
 
Okay that's what I was thinking just wanting to make sure. Yeah I'm sure I can find someone I know with one of these. Now if I did buy one for something like this would I need a big expensive multi channel one? Or would a single channel cheap 60 dollar one work like http://www.ebay.com/itm/2013-New-ARM-DSO201-Portable-Pocket-sized-Handheld-Digital-Storage-Oscilloscope-/221293234021?pt=BI_Oscilloscopes&hash=item33861ac765

I've also seen the now they have scopes that connect to you PC and are multi channel and look more in depth than the cheapy. Which for me works great for my PC is next to my work desk. http://www.ebay.com/itm/Hantek-6022BE-PC-Based-USB-Digital-Storag-Oscilloscope-2Channels-20MHz-48MSa-s-/221270085136?pt=BI_Oscilloscopes&hash=item3384b98e10

I can come back when I have one of these if need be to come what I need to have tested, and how to test them. Thank you guys for your help
 
Don't buy a PC based scope, they really aren't useful for this type of troubleshooting. You can find an earlier model(70's,80's maybe newer)dual trace 20Mhz or better Hitachi,HP or Tektronic scope for around $100 ,but you can use what you have in the MMS in the meantime. Can you take pictures of the circuit board? Maybe three pics,one of the whole board,and two more close ups splitting into two halves(one of the power supply and one of the output) The power supply will have a bigger doughnut shaped coil,the output will have two smaller doughnut shaped coils.I work for Kicker as a repair tech and have worked on many KX750.1's. It may take some time but I can talk you through the repair. I'm thinking the power supply and output mosfets are not burnt or shorted, based on your description. If the power supply where burnt or shorted the Green Power LED would not be lit. If the output mosfets where shorted the Red LED would flash on and off. Does this amp have red vinyl seals running along the top of the amp on both sides,btw? If so, this amp would be an 06KX750.1, if not it would be an 08ZX750.1 or newer. Describe what happens when you power up the amp. The 06KX will have a red and green LED behind an opaque lens,and when first powered up the red LED will be lit and slowly fade out and the Green LED will lit and the clicking sound of the relay can be heard. The 08ZX750.1 only has a red LED on the end panel, and the name badge on the top will light up after a short delay along with the sound of the relay.This sequence can tell you the something's about the amp.
 
Okay this is an 06 Model Kicker 750.1 Amp

I have 4 pictures here two on left of output and two on right for Power
<a href="TinyPic - Free Image Hosting, Photo Sharing & Video Hosting" target="_blank"><img src="http://i42.tinypic.com/vi39c2.jpg" border="0" alt="Image and video hosting by TinyPic"></a>


I also have a video of how I have this all ran and powering on and off
I here a Click when powering off but no sounds while coming on and it seems to be coming from The Blue part next to the capacitors and says 105k100 across the top.
https://www.youtube.com/watch?v=TxCQBx2Amzo&feature=youtu.be

My MMS should be in the mail today, so once you mark what to test and how to test I will be back with part #s and their values.
 
Can you describe your MMS, is it a Digital or analog volt/ohm meter? Some people call them Digilal volt meter (DVM),Volt/Ohm meter(VOM) or Digital Volt meter(DVM). I'm guessing the MMS is another abbreviation for Multimeter,correct? With no power applied,check the resistance/ohms across (outside to outside leads/legs) each of the mosfets. There are ten output mosfets(five on either side of the board), four IRF640's and six IRF9640's. The 640's should read about 50 kohms/each. and the 9640's should be about 33 kohm's/each. There are six power supply mosfets IRF3205's(looking at the pic,these are located in the bottom right hand corner near the power terminals) and should read about 1 kohm's(?)/each. I will look at my schematics/notes when I return to work on Thursday the 26th.
 
An externally hosted image should be here but it was not working when we last tested it.


Use this as a a guide and measure between Pins 1 & 3.

Also, the video showing the sequence of the red and green LED's was textbook and looks like the power supply is healthy and the rails and small supply are coming up to voltage. I was not able to hear the relay turn off. But we will cross that bridge when we get to it.
 
This is a Digital Multimeter with most all basic functions
Current Measurement, AC volt Measurement, Resistance measurement, Diode Test, Transistor Test, Audible Continuity Test, measure frequency, and Capacitance.

Multimeter set to resistance 200k

All IRF640's are from 49.3-49.4
All IRF9640's are from 32.3-32.4
All IRF3205' are 46.4 or .045 @ 2M resistance
 
okay,they are will within range. I quess we should play it safe and return the board back to the chassis. You will only need to bolt in the board and pressure bars.Don't worry about end panels etc...Power up the amp and measure the same mosfets again outside to outside (be very careful with your probes) If you measure one mosfet per bank, you won't need to measure all mosfets. Just measure one 640 and 9640 on either side. Don't worry about the IRF3205's.
 
again be careful not to brush your probe to adjacent leads or pressure bars. you will know immediately when you make a mistake. :-/ try to probe straight in and out. and probe mosfets that are easily accessible. That is why I recommend measuring a minimum # of FETs to lesson the odds. Don't let this discourage you. If you short something out it will add more time and parts to your repair. No Worrys!
 
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