Solid Audio 2500D - pls identify U2 & U3

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nonprof

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Joined 2011
Hello!!! Good Day!

Could somebody help me to find the part number of U2 and U3(maybe identical?) for a driver board of a class D amplifier Solid Audio 2500D?. These drives output MOSFETs.

I'm thinking that this is the culprit of DC offset protect and heating of IRF9640s and IRF640s.

Thank you so much guys! help is very much appreciated...we dont have much resources here in our country. Sorry for my poor camera...

IMG_0710e.jpg
 
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nonprof

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Joined 2011
Perry Babin said:
It's not likely that these parts are defective. The IC with pins 1 and 4 connected is an LM211. The other one is a TL072.
Click to expand...

thanks! for having these numbers.
.
do you have an idea what is the problem? the first problem of this amp is when the relay turns on, it goes to protect. I notice that there is a +80V on the other side of this amp, measured after the output inductor.

Can you please give me one more information? how to find the exact part number of the SMD transistor? It's written as AG and DK (SOT), any technique to get the part number? I broke one of this transistor. I'm planning to order it today, im so very cautious and the list must be complete. It takes a couple weeks and costly when ordering this parts offshore.

thank you so much!

I will try to contribute as I can...I have complete schematics of JL brands, electtromedia/audison amps...
 
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N

nonprof

Member
Joined 2011
nonprof said:
thanks! for having these numbers.
.
do you have an idea what is the problem? the first problem of this amp is when the relay turns on, it goes to protect. I notice that there is a +80V on the other side of this amp, measured after the output inductor.

Can you please give me one more information? how to find the exact part number of the SMD transistor? It's written as AG and DK (SOT), any technique to get the part number? I broke one of this transistor. I'm planning to order it today, im so very cautious and the list must be complete. It takes a couple weeks and costly when ordering this parts offshore.

thank you so much!

I will try to contribute as I can...I have complete schematics of some brands...
Click to expand...
 
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Perry Babin

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bcae1.com
Those driver boards have a lot of problems. The smaller transistors often short or become leaky. The small 470 ohm resistors often open or drift in value. Bad solder connections are common on many of the transistors.

If it's going into protect as the relay clicks, it's likely due to having DC offset on the output transistors. That can be caused by virtually any component on the driver board but most commonly due to an open resistor or defective transistor.
 
N

nonprof

Member
Joined 2011
Perry Babin said:
Those driver boards have a lot of problems. The smaller transistors often short or become leaky. The small 470 ohm resistors often open or drift in value. Bad solder connections are common on many of the transistors.

If it's going into protect as the relay clicks, it's likely due to having DC offset on the output transistors. That can be caused by virtually any component on the driver board but most commonly due to an open resistor or defective transistor.
Click to expand...


thanks! Ill check all of these...
 
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nonprof

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Joined 2011
Guys! Why the capacitors of this amp were blew up again after ran it for 2 days? I replaced the 10 caps with rating are 2200uF/100V and 3600/100V, rail voltages are fine with +-80V. Any ideas why the capacitors keep blowing? thank you very much!
 
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Perry Babin

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Joined 2003
bcae1.com
Caps typically fail when there is excessive ripple current, excessive voltage or reverse polarity.

When you get it working again, confirm that every output transistor has a good drive signal. I don't know if a lack of a proper drive signal on some of the outputs can cause the caps to fail but it's a common problem with these amps.
 
N

nonprof

Member
Joined 2011
Perry Babin said:
Those driver boards have a lot of problems. The smaller transistors often short or become leaky. The small 470 ohm resistors often open or drift in value. Bad solder connections are common on many of the transistors.

If it's going into protect as the relay clicks, it's likely due to having DC offset on the output transistors. That can be caused by virtually any component on the driver board but most commonly due to an open resistor or defective transistor.
Click to expand...

Hi Perry,

Again, I resolder those small transistors and protect goes away, I had done this before the rail capacitors blown up. Now that like before the driver board heats too much...Is it normal to this amp? I'm afraid that if i'll return this amp, another tragedy will happen.

Thank you!
 
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nonprof

Member
Joined 2011
Hello guys,

Why i've seen a little sparks either underneath capacitors or in-between gate resistors? why is this happen? could some fluids, chemical induces the sparks? or do I have unfiltered rail voltages?

I have of bulk of capacitors and half of them were burnt...Is it recommended to replaced them all?

What is the best way to determine a weak rail capacitors? I have a portable oscilloscope.


Thank you very much!
 
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Perry Babin

Member
Joined 2003
bcae1.com
Many times, capacitors will leak which deposits electrolyte onto the board. The electrolyte is conductive and will cause the board to heat between the pads. This can cause the board to carbonize and eventually can cause the board to burn.

This is not likely between gate resistors. Soot from failed FETs can sometimes be conductive but it generally has to be fairly dense for it to cause problems. Have you cleaned to board in those locations so that you could better determine the condition of the board?

If the failed capacitors were in parallel with other capacitors, I'd suggest replacing all in the parallel group.

With the rail caps in the board, you can look at the high frequency ripple on the rail voltage. With the scope set to 2ms and whatever allows the scope to display the trace for the rail voltage (lowest possible setting), look for the line to become 'fuzzy'. That's high frequency noise. This has to be done with the amp driven to full power into its toughest rated load to be meaningful. Removing them and testing them on a proper capacitor tester will provide more definitive results.
 
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