Yamaha DXR15 Powered Speaker Fault LED On

[MobileXT]

Hello Everyone! I have a Yamaha powered speaker DXR15. The problem was the RED LED Fault indicator is steady on when I power the speaker. I did open the module and I don't see any burnt component. I Downloaded the Schematic but I don't know where to start the diagnostic. Any help would be greatly appreciated. I also attached the schematic here

[madan1]

Well, start with the power supply - page 99 -> +/-VB, VDR, +VS, +/-18A, +5V. Check if all that power rails are present. Then check the DSP board and see if the +/-15, +6V, +5 and +3.3 rails are generated.

[MobileXT]

Thank you! and found that Q107 was shorted to ground. I order the replacement parts and I will update soon once I get the parts.

[MobileXT]

Update: After replacement of the Q107 still have the same issue Q107 still getting hot from the infrared camera. Q106 is not shorted, I Removed Q106 and there's no reading on the diode mode drain and source. Testing D10 with Diode Mode seems like D104 is not shorted.

[madan1]

If you have a red LED or indeed any other LED, then you have +5LD rail, +6V, +18A and DC+25V power rails, all of them are on the secondary/low-voltage side of the power supply. This most likely means that the primary side is working.

[MobileXT]

That’s good to know, I will concentrate on the secondary or the amp output. Thanks for the tips.

[MobileXT]

After hours, days and months of trouble shooting. I finally ordered the AMP board and replaced it with a new one. Sadly, still have the same problem Protection mode still ON. I did all check the power rail on the DSP and all the power rail are present. So I did check on the tweeter AMP and measure 27V at the speaker output. SO I am pointing to the AMP IC TDA8922CTH is BAD but I need you guys expert on this one.

[CapLeaker]

Yeah… switched wrong amp board. Remove the TDA IC from the board and reinstall the board see if your DC disappears on the tweeter.

[MobileXT]

Okay After removed the TDA the 27V at the tweeter output still present. I attached a measurement after removal of the TDA.

[R_J]

`What point are you using for ground when checking the tweeter voltage? Check what voltage you have ACROSS the tweeter terminals, the supply to this ic is +55v, half would be around +27v measured to PGround
The speaker is connected across the two outputs of the ic.
Are you able to power on the amp without the tweeter amp board connected?

[MobileXT]

I measure from ground to the tweeter terminal I got 27V each channel. If I measure from the two Channel ACROSS tweeter output I have 0V without the TDA AMP. Yes I can still power on the AMP without the Tweeter AMP board but I have a Protection circuit ON.

[CapLeaker]

You measured the tweeter voltage wrong (should have been like 55V across the speaker terminal), but that’s o.k. At least the speaker works without the tweeter amp. It could be that over the time heating and cooling cycles, the TDA’s legs may develop cold solder joints, thus triggering the protection. At least you are on the right track now.

[MobileXT]

Thanks CapLeaker! You think TDA AMP chip is Okay to solder it back now?. I ordered a new one should be here now in a couple of days. I have two speakers have the same issue. I might open it up the other speaker check for the legs on the TDA8922CTH legs for cold solder joints.

[CapLeaker]

Any class D brick style with these 1000 little legs can develop that problem. My first goto is looking for cold solder joints on the class D brick and then resolder and try. Anything that gets hot and has a heat sink on it. Followed by all power supply rails measurments

[R_J]

I measure from ground to the tweeter terminal I got 27V each channel. If I measure from the two Channel ACROSS tweeter output I have 0V without the TDA AMP. Yes I can still power on the AMP without the Tweeter AMP board but I have a Protection circuit ON.

If you replaced the amp/power board and disconnect CN501 (twamp) and still have the protection led, check CN255 pins 15 (DC_DET) and 16 (AMP_ERR) to see which line is enabling the protection.

IC501 is operating in btl (bridge mode) so KG is common or signal ground

[MobileXT]

Okay! here is the results for the CN255 PIN 15(DC_DET)= 0.020v and PIN 16(AMP_ERR)=3.296V. Measured from the ground to PIN 15,16. without the Tweeter amp board.

[R_J]

Looks like DC_DET is logic low, not sure what it should be I suspect it should be +3.3v . There is a DC detect check test point (page 104 k,3) it seems to have logic levels, check those pins, maybe it will show something wrong
This is not a simple system, they monitor a lot of things, and anyone could cause a fault. and they don't really say if a logic high or low is normal operation or with fault.