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Old 16th May 2005, 11:58 PM   #1
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Default xplod amp blown please help

I have a sony xplod xm2165gtx that i got from a friend. The problem is that he blew it up some how. I believe he hooked the positive to the negative and the negative to the positive. I don't know too much about this but i think with a little help i could figure out what's wrong. There is a row of 8 black transistor looking things but i'm not sure exactly what they are and the ones that are melted are melted so bad i can't read the numbers to find replacements for them. Please help i would greatly appreciate it.
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Old 17th May 2005, 12:53 AM   #2
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They are likely the power supply MOSFET's, and the clamping reverse polarity diode must be blown too.

The MOSFET's are commonly the cheap IRF Z44 or similar, as far as the diode goes pretty much anything will work.

You will also have other problems to contend with, it is probable all the input filtering caps are now dead as well and possibly also many other parts depending on the way the Sony was designed.





-Matt
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Old 17th May 2005, 04:59 PM   #3
sdoom is offline sdoom  Germany
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As zagisrule! alreadys said, the Diode is most likely to be blown. You can check that with a multimeter (diode-testing mode) . Your meter should then read fully open , or if connected vice versa around 0,5V . the diode is most likely to be broken. You can cut one leg of it for testing purposes. If you need to replace it, any power diode with 50V /3A (or more) will do the work, this diode has no work to do, it is only there for that case, someone mixes up +12V and GND terminals.



But you will probably get a real short. Then you need to take out the Mosfets from the power supply section. Once they are out connect a small car battery charger (12V 3A will do fine) to +12V and GND terminals. use a short piece of wire that you can connect between the +12 terminal and the RMT-terminal. The amplifier should not draw more than 200mA current when the mosfets are out.

If you are not 100% sure, connect a 12V light bulb in series to the amplifier +12V power terminal. If the amp still has a big fault, the bulb will glow. then immediatly turn off the power.

If the bulb stays dark, get a scope. Turn on the 12V and connect the RMT signal so that the amplifier tries to turn on. Connect one wire from your scope to GND. The other wire from your scope goes to that curcuit line, that would connect each Mosfetīs left leg. (left leg if the Mosfet was looking towards you). Now this is the curcuit that will turn on and off the Mosfets. You should get nice squares , aprox 20kHz-40kHz.

Check this with all curcuit lines that woul go to each Mosfet.

I wouldnīt worry too much about the capacitors. most of them are pretty tough . as long as they are not blown, leaking or look like a mushroom, they should be fine.


Problem with the Mosfets is, Sony doesnīt use standard devices like zagisrule! said. Sometimes Sony uses Mosfets that are very hard to get or very expensive. the most common Mosfet I have seen in Sony is the IRF540 and IRF9540 used in the music amplifiers.

You can try to use IRFZ44 devices (or SSP50N06 or similar) . But then you really have to monitor the voltage with a scope to see if those devices are acting fast enough and dont cause trouble.

If you can get some part of the Mosfet name we can try to find a replacement part.


Steph
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Old 18th May 2005, 03:46 AM   #4
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Unhappy got the number

The number on the mosfets is fkv550 and i believe all six of them have the same number. i would really appreciate it if you could help i'm getting frustrated and i'm pretty sure the diodes are good they look to be in good shape there is two of the a fch10a15 and an frh10a15 but i hope it's only the mosfets because those are melted and everything else looks fine. Thanks again hope to hear from you soon.
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Old 18th May 2005, 01:30 PM   #5
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Click the image to open in full size.

Is this what i t looks like ? If you need to replace FKV550T , All i can
say is good luck. I remember looking for them myself and there about 6 dollars each, for me it would be around 50 dollars not worth it for a sony that you can buy off ebay for 80 dollars. you could try irfz40 and mica washers, and make something to clamp the transistors down to the heat sink. It's only a suggestion.
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Old 18th May 2005, 05:12 PM   #6
sdoom is offline sdoom  Germany
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I also agree the the FKV550T is most likely to be very expensive or hard to get.

there are a couple of other Mosfets around that also have a fully isolated package. I think there are IRFZ4x around with plastic packages, too.

Before you start looking around for the Mosfets, dissassemble them from the board and check the gate resistor signals with a scope. if you donīt get any squarewave signal, even more of the amplifier is damaged. That could be a broken transistor / mosfet from the music section (most likely) or the PWM-controller itself or the small (SMD) driving transistors are fried. If it is like this, then part it out or sell it on ebay as a broken amplifier.

the mosfets in the music section should be IRF540 and IRF9540. they are pretty common.


I just checked the datasheets for the FKV550T and the IRFZ44. They are pretty close, so if you are lucky, those would work (IRFZ44 is ~ 70 cents each). You would have to use insulating foil for the IRFZīs , but that shouldnīt be a problem.

I would give it a try with the IRFZ.

There has to be a big power-diode near the power-terminals. this diode needs to be checked, if your friend mixed up + and - cables. Usually this diode is fried and causes a permanent short. replace it with any power-diode (30V/3A or more) . Also check the mosfets in the music section with an ohmmeter, if you find a short there, the mosfets are also fried.

When you decide to give the IRFZīs a try use the above method to power up the amplifier. That means connect a 12V/10W light bulb or a 3,3Ohm/10W in series to the + power cable. If the amplifier had a fault, it would cause a very high current draw. With the bulb in series, the current causes the voltage to be dropped at the bulb . this will prevent the amplifier from burning parts.

If the amplifier is fine, you can run it at normal speaking level even with the bulb in between. If that is fine, get rid off the bulb and try the amplifier w/o it. Also, only use a 5 or 10A fuse for testing purposes.

Steph
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Old 19th May 2005, 12:02 AM   #7
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Default a little more help

Ok that is what the amp looks like but sdoom i'm not sure how to do the stuff you described to do if you could possibly go deeper into detail about what kind of meter is used and how to do it i would be ever so greatful. Thanks
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Old 19th May 2005, 04:55 PM   #8
sdoom is offline sdoom  Germany
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hi


ok, when it comes to fixing SMPS you should always have access to an oscilloscope. With the scope you can monitor the voltages and check how good/poor the signals look like.

If you have not disassembled the ampifier already, do it. Get a multimeter, switch it to Resistor-Mode (=Ohmmeter) and check each leg of the Mosfets from the Music-amplifier section. Those should be on both outer sides ( If I remember right, those are IRF540 and IRF9540). Check each leg to another from every single Mosfet transistor. If you find a short (=0 ohms) the mosfet is fried and needs to be replaced.

If there is no short in the music section you take out all the FKV550T from the power supply section. Watch the solder-points. Once the FKV550T are out make sure that there is no solder left on that part of the curcuit board which could cause shorts.


Then connect your ohmmeter to the +12V and GND (= power) terminals. If there is a short (=0Ohms) some other parts are fried, too.

Then check the diode, that is mounted close to the power- terminals. This diode is connected in reverse to the +12V and the GND curcuit lines, you can easily find the diode by following the curcuit lines from the terminals. Cut the diode out. Again check the resistance between the +12V and the GND terminal. There should be some resistance now.


If there is no short between the +12V and the GND terminal , you will have to check if the switching curcuit is working properly or not. To do so, hook up the amplifier to a power supply unit (car battery charger or some kind of 12V DC power supply) like it is shown in the picture.


Click the image to open in full size.


Now turn on the amplifier with the switch. Use the oscilloscope to monitor the switching signals. To do so, connect one wire from the scope to GND. the second wire from the scope goes to the spot , where the gate from the first FKV550T is normally connected to. Here is a picture of the mosfet legs.

Click the image to open in full size.

You should get a nice square wave form with an amplitude around 12V. Check each spot , where the gate aof each FKV550T is usually connected to. If there is always a nice squarewave signal , the controller unit has survived.

Then disconnect all wires from your 12V power supply. Get the IRFZ44 or your spare mosfets and install those (use insulation foil)
Connect the power supply again and power up the amplifier. Listen for high frequency noise coming out off the transformer and monitor the Sony indicator lights. If you made it this far check the gates (mosfets) again with the scope. There has to be a nice square wave signal. Be careful not to cause a short with the test prod. If this thing is running, turn the amplifier off. Connect a speaker to one channel and use a discman / MP3 player as a source unit. Turn down the gain all the way. Turn down the output volume of your source unit all the way. Turn on the amplifier and start playing music with source unit. slowly increase the volume. If you hear music w/o distortion, thatīs a good sign .

Turn the amp off. Connect the speaker to the other channel. Repeat the test . Donīt turn up the volume too much and donīt let the amplifier run for more than 2-3 minutes (remember the transistors do not have their heat sink yet) . always have a break between each test and check the power transistors for heat !

If this is running, assemble the whole amplifier and test it with a bigger speaker.


Steph
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Old 27th August 2005, 04:50 PM   #9
bthbmx is offline bthbmx  United States
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Default the answer

everybody here is saying that the little mosfets will be expensive and hard to find. they are also saying that you should buy a new amp or replace the mosfets with somthing else. well...has anyone thought of calling sony? the same thing hapend to my amp. 3 of the little mosfets blew. i did a lot of reasearch to se if i could fix it. i looked on here and many other places. then i figured why dont i call the people who made the amp. so my sugestion is call sony and buy the peices. it only cost me $10 to get 3 shiped to me.
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Old 27th August 2005, 05:47 PM   #10
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The fully insulated version of the irfz44 is the IRFIZ44.
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