Hi guys, I had a dead Xetec Gravity G500 monoblock on hand, the power supply keep dropped into the short circuit protection mode. Someone has messed with it before but seemed no luck yet more torn PCB pads.
After I remove the module with defaced chip, which I think most likely to be the Class-D modulator, the amp was able to power up without any output.
I wanna ask is anyone had the schematics or able to identify the defaced chip?
After I remove the module with defaced chip, which I think most likely to be the Class-D modulator, the amp was able to power up without any output.
I wanna ask is anyone had the schematics or able to identify the defaced chip?
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That amp appears to be a scaled down version of this basic type of class D amp.
http://www.bcae1.com/temp/bp1200p1_sm.pdf
The IC is an MC14060. U106 in the service manual.
http://www.bcae1.com/temp/bp1200p1_sm.pdf
The IC is an MC14060. U106 in the service manual.
The service manual you provide is very similar to the Class D module. Yes, I do have scope, and you're right the IC didn't fail.
I removed the output FETs to check for the switching waveform, but it only present DC voltage to the gate pin. Right now the module has triangular wave around 80khz input to the LM361N pin 4, but only DC -15V is input to the pin 3, and around DC 5V output on pin 11, doesn't react to analog input signal.
I think I need to understand more on how each section works.
I removed the output FETs to check for the switching waveform, but it only present DC voltage to the gate pin. Right now the module has triangular wave around 80khz input to the LM361N pin 4, but only DC -15V is input to the pin 3, and around DC 5V output on pin 11, doesn't react to analog input signal.
I think I need to understand more on how each section works.
It was much different on that part, but I went through the issue. The audio input op-amp was faulty, like in the U105A.
I can't get the switching waveform from the LM361N output without the feedback from the output stage. But without feedback, I was able to check it by short circuit the input op-amp pin 1 and pin 2 like the U105A in the diagram.
Right now I'm facing another problem where I was able to get the output to start switching, but very high current draw.
The switching frequency was at 80.6Khz, is it normal?
I can't get the switching waveform from the LM361N output without the feedback from the output stage. But without feedback, I was able to check it by short circuit the input op-amp pin 1 and pin 2 like the U105A in the diagram.
Right now I'm facing another problem where I was able to get the output to start switching, but very high current draw.
The switching frequency was at 80.6Khz, is it normal?
This is what I got.
Later then I tried screw back to chassis for cooling and crank up the current limit, it was able work. But sometimes it take very high current, >10A way over my bench supply limit to start, then it cycles in protection state.
When it was able to on, the idle current is ~1.8A @ 14.4V and 2.7A @ 12.8V. It seemed higher than usual car amplifiers.
Sounds ok and good when it is running.
Later then I tried screw back to chassis for cooling and crank up the current limit, it was able work. But sometimes it take very high current, >10A way over my bench supply limit to start, then it cycles in protection state.
When it was able to on, the idle current is ~1.8A @ 14.4V and 2.7A @ 12.8V. It seemed higher than usual car amplifiers.
Sounds ok and good when it is running.
Attachments
It's odd that the current increases at lower 12v supply voltage. That typically indicates a drive problem. It may be normal for this amp. I don't know anything about the power supply drive circuit beyond what you posted.
The 10 amps to start isn't likely a problem if the current drops back down after the rail caps charge.
The initial photos you posted seemed to show some sort of problem with the insulation on the inductor. I don't know if that was a real problem or just an illusion.
The audio drive signals look OK but the final test is generally whether the FETs heat quickly or not. If there is a question, clamp them tightly to the heatsink (with new heatsink compound) and let it idle for 10-15 minutes. Does the heatsink heat up significantly?
The 10 amps to start isn't likely a problem if the current drops back down after the rail caps charge.
The initial photos you posted seemed to show some sort of problem with the insulation on the inductor. I don't know if that was a real problem or just an illusion.
The audio drive signals look OK but the final test is generally whether the FETs heat quickly or not. If there is a question, clamp them tightly to the heatsink (with new heatsink compound) and let it idle for 10-15 minutes. Does the heatsink heat up significantly?
Yes the isolation is okay. Out of the housing it can't turn on for long, the FETs will get very hot. Output filter coil and transformer looks okay too.
Have you try to run your G1200 under a current limit condition? Like how does it react when it hits current limit from the supply side.
Which part of the inductor you saw have insulation problem?
The amp heatsink gets warm after 10-15mins, and operates around the same temperature on idle for hours.
On the inductor, it was the top coil where it was pulled away from the rest of the windings.
Bertje will be able to tell you what's normal but slight heating, especially when it stabilizes is typically OK. Very slight differences in replaced components can cause the dead time to be too low which can cause heating. In these amps, I generally used the (discontinued) IRFB31N20D that eliminated the heating of the output, but either way, the amps were reliable.
Bertje will be able to tell you what's normal but slight heating, especially when it stabilizes is typically OK. Very slight differences in replaced components can cause the dead time to be too low which can cause heating. In these amps, I generally used the (discontinued) IRFB31N20D that eliminated the heating of the output, but either way, the amps were reliable.
As a shop I sold these Xetec amps a lot, and they had a low failure rate. I don't have them on stock for many years, Xetec stopped in 2007/8 ...long time ago.
When switching on it has the normal inrush current peak, like any other amp, within 1 second or less is idles about 2A as I remember correctly.
When loaded with 4 or 2 ohm resistive dummyload, just check the current draw and heat carefully. Maybe it's just normal and ok...
When switching on it has the normal inrush current peak, like any other amp, within 1 second or less is idles about 2A as I remember correctly.
When loaded with 4 or 2 ohm resistive dummyload, just check the current draw and heat carefully. Maybe it's just normal and ok...
I tested it again on a car battery supply directly, there is no startup and cycles in protection issue, everything seemed normal and fine.
Heat and current draw are maintained, as long as the driver board transistors is contacted with the bottom cover with thick thermal pad for some cooling. The current draw will slowly goes up to about 2.7A if the bottom cover is left open.
For now I think considered good and normal for this amp.
Heat and current draw are maintained, as long as the driver board transistors is contacted with the bottom cover with thick thermal pad for some cooling. The current draw will slowly goes up to about 2.7A if the bottom cover is left open.
For now I think considered good and normal for this amp.