Kicker ZX750.1 troubleshooting resistors - diyAudio
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Old 27th March 2016, 10:02 PM   #1
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Exclamation Kicker ZX750.1 troubleshooting resistors

Hi!

A couple of weeks ago i went to my attic and found my kicker 750.1 and the L7 sub that i used in my previous car. I dicided to try it out in my forester, everything worked for a week or two until today.
I started up the car and played a song but there was no sound from the subwoofer, the amplifier lights were on and there was no light from the protection mode lamp.
I started to disconnect the wires and when i disconnected the cable to the subwoofer the amp started to cycle from on to off, with the protection mode light blinking as it turned on and off.
When i only have power wires connected to it, it cycles from on to off. But when i connect the subwoofer cables, the amp starts up and there is a click sound in the subwoofer. The amp remains on but there is no sound output.
I measured the power to the amp and everything looks fine, but i can't measure any output when I'm playing music.

Opened it up now and started to measure resistors, then i came across r171 wich is a 3,3kohm resistor, but i only measure 2,2kohms. There are 4 other 3,3kohm resistors nearby that seems fine, but the colour is not the same as the one thats broken.. Is this a sign of high temps or is it supposed to be this way?

And, is it most likely the r171 resistor that is causing the amp to not work?

Sorry for my bad english, Im from Norway
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Old 27th March 2016, 11:29 PM   #2
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That resistor is part of the over-current protection circuit. It drops voltage to D111 (12v Zener). It's common for them to become darkened from heat. If it's out of tolerance, it needs to be replaced but isn't likely preventing the amp from working.

The click from the speaker when the relay engages is likely due to excessive DC on the output. The amp is shutting the output down to protect the speaker.

Check D111 to confirm that it's not shorted.

A forum member (papaZBill) is a kicker tech and will be able to guide you through the repair (if you want to attempt to repair it) more efficiently than I can. If he doesn't check in a doay or so, I'll try to help.
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Old 28th March 2016, 12:15 AM   #3
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Do i need to buy some kind of high quality resistor to replace the broken one?
I was hoping to fix The amp myself if it isnt superhard?
Thanks for fast reply!
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Old 28th March 2016, 12:30 AM   #4
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Nothing special but you may want to go to the next higher wattage rating. A larger physical size will have more surface area and be able to dissipate the heat a bit better.

There are threads for other amps like yours. Do a search of this forum for the amp model number and read through the threads. That will give you an idea of what's involved and may help you to become more familiar with the operation of the amp.
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Old 28th March 2016, 12:37 AM   #5
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Okay, thanks m8! Im not so good at this, but i wil try!
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Old 28th March 2016, 04:47 PM   #6
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Post good quality photos of amp, one overall and another of the area around R171.

Do you have a soldering iron with a pencil and chisel tips, a 12v power supply and a good Volt/Ohm meter? If you have any other other test equipment such as oscilloscopes or signal generators they can be useful if you know how to use them, but not necessary.

You can disable the protection circuit by lifting R35. If you orient the amp with power terminals on your right you will find R35 in top right hand corner near Q03.

When you have R35 lifted make sure that you do not have anything connected to speaker terminals and power up amp, does this allow amp to come out of protection?(You may hear the relay click on and the Red LED will be off)

If you are not sure about any of this please ask as many questions as you need to, I will walk you through this a slowly as necessary. Feel free to send me PM's as well.

Perry and others on this forum can and will help you out if I can't get back to you in a timely manner.
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Old 29th March 2016, 07:10 PM   #7
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I have a 12v power supply, solder iron with both tips and a good volt/ohm meter.

I will try to lift the r35 when i have time, i will post as soon as its done! Thanks!

Here are some pictures.
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Old 29th March 2016, 08:16 PM   #8
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Okay, so i successfully lifted the R35 and powered the amp. When i powered up the amp the red LED flashed once and then lighted up for a couple of seconds then repeated once more (not sure if the power supply is causing this? It was making a buzz sound when the LED flashed?). Then the relay clicked and the LED turned off.
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Old 29th March 2016, 08:38 PM   #9
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You have an option to have a sig line. As you've probably seen, some use it to list the test equipment that they have. Knowing what you have helps when others are offering suggestions during the repair. Having the make and model of the power supply, multimeter, soldering iron, scope (list 'no scope' if you don't have one)... will make it easier to help you. This doesn't apply only to you. It's for anyone asking for help with amp repairs.
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Old 30th March 2016, 03:01 AM   #10
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As Perry states, knowing the make and model of the your test equipment will help in determining if in this case the power supply is not allowing the amp to power up properly, in other words not able to supply enough current. Google recommended power supplies for testing car audio amplifiers. Perry's website http://www.bcae1.com/ is a wealth of information on Basic car audio repair.

If you haven’t already remove R171 and check with an ohmmeter, and then check the ohms at the location of R171.The 2.2 k ohm reading is most likely a result of a parallel connected component such as D111,U17 or C146,C147. This may be the reason for the abnormal indications your getting when you power up the amp.

Whenever you are removing components, make sure that all power cables are disconnected and it's recommended that you test amp with the board clamped down in the chassis.
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Last edited by PapaZBill; 30th March 2016 at 03:09 AM.
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