Unknow mosfet

[picco76]

Hi, i have on JL 300/2 4x irf540 and 4x unknow mosfet, somepeople know this mosfet? I don't found info about this device...

 

[Perry Babin]

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[picco76]

Done

 

[Perry Babin]

All of the outputs in the 300/2 are the IRF540.

 

[picco76]

All of the outputs in the 300/2 are the IRF540.

Ah ok, thanks, but don't is strange? This ampli have 4x IRF540 and 4x this unknow mos..

 

[Perry Babin]

I did this work for more than 30 years. Nothing really surprises me anymore. They could have been installed by anyone. The solder doesn't look like flow soldering.

 

[picco76]

Ok, maybe, i don't know..
Maybe you know voltage bias adjust on ceramic resistor for this amplifier?

 

[Perry Babin]

I don't know what the factory recommends. I've found a lot at 4mv which I believe is excessive. I prefer setting them as in the demo below:
http://www.bcae1.com/temp/ausettingbias.swf

 

[quasi]

Ah ok, thanks, but don't is strange? This ampli have 4x IRF540 and 4x this unknow mos..

I could not find that part number but it could be a fast schottky rectifier similar to this. https://static6.arrow.com/aropdfcon...21ff47d54a448a832ed42182/sdp20s30_rev.1.4.pdf

It might be sitting near / connected to the coil. Do you have a schematic?

 

[nigelwright7557]

IR9118 comes up as Chinese mosfet.

 

[quasi]

Hmm...schematic will show I guess.

 

[picco76]

I have changed all r-channel mosfet, but i have this situation on power supply mosfet, drain pin (see picture).
The amplifier work normally, but after 5 min. The square wave is unstable and i hear the strange sound from power supply ( i think from toroid)

 

[Perry Babin]

What are you powering the amp with?

How high is the DC voltage feeding the amp after 5 minutes?

If you lower the 12v power supply voltage, that waveform will probably look more like you're expecting.

 

[picco76]

What are you powering the amp with?

How high is the DC voltage feeding the amp after 5 minutes?

If you lower the 12v power supply voltage, that waveform will probably look more like you're expecting.

I powering with 40A switching power supply, 12.6V.
What is "dc voltage feeding the amp"? You mean rail voltage?

 

[Perry Babin]

is the voltage steady at 12.6v?

Is it adjustable?

 

[picco76]

is the voltage steady at 12.6v?

Is it adjustable?

Yes, i have tryed also with 14.0V, but is the same. I have this square wave unstable also on sg3525 output..

 

[Perry Babin]

If you play music at a fairly high level, does the amp do this?

Does it produce music normally when the instability starts?

 

[picco76]

is the voltage steady at 12.6v?

Is it adjustable?

Yes, i have tryed also with 14.0V, but is the same. I have this square wave unstable also on sg3525 output..

 

[picco76]

If you play music at a fairly high level, does the amp do this?

i have played low volume music, i must try with high volume.

Does it produce music normally when the instability starts?

i don't know, let you know.

i have misured also square wave on SG3525 output, is clean, but when instability start (change frequency), also this square wave is unstable. can be sg3525 broken?

 

[Perry Babin]

I doubt that the is a defective 3525.

We need to check quite a few more things. For now, test at high power.