My alpine amp makes a high pitch squeaking sound

[weesatron]

Today when i went to turn on the stereo in my car my sub woofer amp wasn't putting out any sound. So i checked my crossover, curict barker,cables,sub and all that stuff and was all fine so i took it inside to test it with a atx power supply and noticed it was making a hi pitch squeaking sound so disconnected the speaker i was testing it with but the sound was coming out of the amp its self so i open it up to take a look inside cant see any cracked/dry solder joints and nothing looks burnt i just cant figure out why the amp squeaks

so if any of you guys have any idea's what the problem is please let me know

the model number is alpine 3539 if that helps
the area circled in red appears to be where the noise is coming from

 

[an2ny888]

mine makes the same sound as well, works fine though

 

[Perry Babin]

The 12v output of many ATX supplies is not regulated. With no significant load on the 5v output, the 12v output may be very noisy and may cause the switching power supply in the amp to produce noise.

You need to troubleshoot the problem in the vehicle if it produced audio on the ATX supply. With a multimeter, you need to check the voltage at the terminals of the amp to confirm that you have ~12v on the B+ and remote terminals (black meter probe on the ground terminal of the amplifier).

 

[weesatron]

just tried running it off a car battery and it dose the same thing also do you know what components make noise when they fail

 

[weesatron]

if any one has the curict diagram that would also be helpful

 

[weesatron]

i just ran a moor thorougher test and found out the right channel works but is distorted and the left dose nothing could it be one of the power transistors?

 

[lumanauw]

You have to replace the capacitors, especially the 12V input capacitors, like the ones above the green chokes in your pic.
In old alpine amps, these capacitors usually already leaking.

 

[weesatron]

do you know websites that would sell replacements for the 2 big ones because the local electronics shop dosent sell them

 

[I Am An Idiot]

Before you go changing parts, I really think you need to find the problem. If you do have an output transistor problem, the amp could be pulling extra current and placing the power supply in a bind, this could cause an audible noise coming from the supply. I would put a 5 amp fuse in the amp and see if it blows that fuse. Power the amp up with whatever fuse you have in it. Turn it off and quickly replace the fuse with a 5 amp fuse, power it back up. If it blows the fuse you have a possible current draw problem. The reason I said quickly was to not allow the capacitors to discharge. If they discharge, it may pull more than 5 amps briefly when powering up.

 

[weesatron]

ill try that i think it is drawing quite a bit of current because the power cables get abit hot

 

[I Am An Idiot]

Don't waste the time with the 5 amp fuse. If the cables are getting hot, I am sure it is pulling extra current. Do you have an Ohm meter? If so set it to the diode test function, it should be the only picture on the selection knob. The output transistors are the 4 large green ones and the 4 large black ones right next to the green ones. Using the meter touch and hold one lead to the middle leg of a transistor, and touch the other lead to first the right leg of the same transistor, notice the reading, then move the lead from the right leg to the left leg, notice that reading also. You need to repeat for all 8 transistors. Do not cut any legs off of the transistors yet. Chances are there is one bad green one and one bad black one. There are 2 greens and 2 blacks per channel. You will need to replace all 4 of them. 2 Green and 2 black, but we can determine which one is bad and you can cut it out, you can then test the amp,(at very low volume) if it works and sounds right, then you know you have no driver problems. If it works it will be as simple as replacing the 4 outputs. One set of them will show very near .004 the good set of transistors will not read anywhere near that. let us know what you find out.

 

[weesatron]

i unsoldered all 8 from the board 3 gree ones and 3 black ones read about 700 and 1 black and 1 green one read as 001

 

[Perry Babin]

The ones that read 001 out of the board are defective.

What are the numbers on the defective transistors?

 

[weesatron]

i put the good ones back in and 1 channel works fine now the numbers are a1265n and c3182n im guseing that they have been discontinued by now dose any one know what the replacement would be?

 

[Perry Babin]

Add a 2S prefix to the numbers.

2SA1265N
2SC3182N

An ebay seller has both.

I don't know if the N suffix is important. 2SA1265 and 2SC3182 are likely the same exact part. The following are from MCM.

http://www.mcmelectronics.com/product/MCM-TOSHIBA-2SC3182N-/2SC3182

http://www.mcmelectronics.com/product/2SA1265

 

[weesatron]

is there any other components i should test before putting in any new transistors

 

[Perry Babin]

You should take the transistors from the good channel and install them in the dead channel to confirm that there are no other problems with the dead channel.

Insert a 10 amp fuse in the B+ supply line to protect the amp in case there are problems with the dead channel. All transistors should be clamped tightly to the sink before applying power.

You should also check the large white emitter resistors. Pull them out of the circuit. They should read the rated resistance (printed on the resistor) from the center leg to each outer leg.

 

[weesatron]

just tested it with the good transistors in dodgy channel and the sound came back so tested all the transistors again and all were fine so i removed them one by one and found out that when the one circled in the attachment is removed the sound disappears

 

[Perry Babin]

Did you check the resistors?

Do you still have transistors that read 001 out of the circuit?

 

[weesatron]

yes tested resistor but i will double check just in case and the dud transistors were removed from the board

should thees transistors work in place of the dead ones

http://www.sicom.co.nz/xurl/functio.../0/searchtext/6333313832/grpid/0/content.html

http://www.sicom.co.nz/xurl/functio.../0/searchtext/6131323635/grpid/0/content.html