My alpine amp makes a high pitch squeaking sound

[wg_ski]

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

And with those old obsolete parts, I wouldn't trust E-bay any further than I could throw it. Chances of getting a phony are very very very high. I would use the Fairchild FJA4310/4210 (140V) or the FJA4313/4213 (230V) from Digi-key.

 

[Perry Babin]

There are 4 resistors (large, white, 3 legs) that you need to check.

Those are the correct transistors. You need to replace all 4 (2 of each) in the channel that failed.

 

[weesatron]

when im testing the resistors do i subtract the reading i get when i touch the two leads together from the reading i get from the resistor?

 

[Perry Babin]

Yes. You won't read precisely the rated value but you should read something very close (within ~10%).

 

[weesatron]

just tried the amp again with a good set of transistors in dud channel and all the resistors are fine what could of caused the transistors to die in the first place

 

[Perry Babin]

In an amp this old, some of the failures will be due to age. In most cases with newer amps, output transistors fail because speaker wires short together or the amp is driven into a load with an impedance that's too low.

 

[I Am An Idiot]

Sice you jumped the gun and pulled all of the transistors out of the circuit, and probably do not know which transistor was paired with the failed one, shouldn't he really replace all 8 of them?

 

[weesatron]

when i take the transistors from the good channel and put then in the bad channel that sound comes back then when i put them back in the other channel it works again so there must be something else wrong with the bad channel could it be some of the transistors on the power supply side of the board

 

[I Am An Idiot]

No do not pull the power supply transistors out. They are not your problem. You more than likely have a problem with the driver transistors on the bad channel.

 

[weesatron]

where would that be located

 

[I Am An Idiot]

Upon closer inspection of your picture, that amplifier has a chip that drives the transistors. As far as I remember, they very rarely failed. I really don't recommend pulling the driver chips until you determine that there is a problem with said chip. Did you check the 4 3 legged resistors? Maybe Perry will have some help for you.

 

[weesatron]

yep checked them

 

[ppia600]

/\ I don't think one or more of those emitter resistors being open would cause any oscillation, those are regular PnP and NpN output transistors, right?


So it has two seperate IC's, one to drive each channel's output transistors? Those are the two with the aluminum sinks, correct? Unless its something before the IC's, maybe between there and the rca jacks, I would suspect the driver IC in the cranky channel's circuit. Just looks like too simple of a circuit for anything else. But you never know what the amp's been through in its long life, lol.

 

[weesatron]

year i brought this off a guy that i brought a broken amp off before but managed to fix it just had some cracked solder joints when i got the alpine amp the right rca input had a cracked joint so the right channel has only been used recently so the left channel has had a lot moar use then the right one might have something to do with why it died

 

[weesatron]

/\ I don't think one or more of those emitter resistors being open would cause any oscillation, those are regular PnP and NpN output transistors, right?


So it has two seperate IC's, one to drive each channel's output transistors? Those are the two with the aluminum sinks, correct? Unless its something before the IC's, maybe between there and the rca jacks, I would suspect the driver IC in the cranky channel's circuit. Just looks like too simple of a circuit for anything else. But you never know what the amp's been through in its long life, lol.

as far as i know they are

 

[weesatron]

just tested the small green transistor on the dead channel and gets a reading of 001 should i swap it with the one from the good channel and see if that changes anything?

 

[Perry Babin]

If the driver transistor reads anything near 0 ohms across any of its terminals out of the board, it's defective. You can pull the one from the good channel to try it in the defective channel. Check all of the outputs that you use in the defective channel before installing them to confirm that none are shorted.

Are the driver ICs UPC1298s?

 

[weesatron]

tried the transistor the squeaking sound has gone away and the channel works for about 30 second then shuts down are the driver ICs the ones on the 2 heatsinks the numbers ive got are upc1225h

 

[Perry Babin]

The 1225 is the driver IC.

The amp may be going into protect mode. Are all of the emitter resistors back in the board?

 

[weesatron]

yep there all in