Burnt components in USB DAC + help in identifying

[imp]

Hi,

my collegue showed me his USB DAC (HRT Music Streamer II + 2010 edition) today which have some not entirely burnt but well overheated components, and we´re trying to figure out what happend and why. In the attached image you can see T101 and T102, someone recognises them? What are they? Small transformers?

Also, one pin of the U107 (ZXMHC3A01T8, "COMPLEMENTARY 30V ENHANCEMENT MODE MOSFET H-BRIDGE") has run very warm as you can see. Now the unit's completely dead ....

We´ll try to replace U107 but anything else to consider?

Any help appreciated!

[ben7]

Re: Burnt components in USB DAC + help in identifying

Hi,

my collegue showed me his USB DAC (HRT Music Streamer II + 2010 edition) today which have some not entirely burnt but well overheated components, and we´re trying to figure out what happend and why. In the attached image you can see T101 and T102, someone recognises them? What are they? Small transformers?

Also, one pin of the U107 (ZXMHC3A01T8, "COMPLEMENTARY 30V ENHANCEMENT MODE MOSFET H-BRIDGE") has run very warm as you can see. Now the unit's completely dead ....

We´ll try to replace U107 but anything else to consider?

Any help appreciated!

Yes, those are some type of smd inductors.

Probably the h-bridge and the inductors are used in a power regulating circuit.

If they are, I don't like how there is barely and way for heat to be sucked away from the h-bridge; thats why it has overheated.

Also, finding a similar drop-in part would be hard. it would be good to use a better replacement though (lower Rds-on)

[budm]

Re: Burnt components in USB DAC + help in identifying

This is what I think from looking at the pictures: That U107 and T1, T2 is part of the switching power supply circuits for producing + and - voltages for the OP-AMPs. Check D101, 102 rectifier diodes, DC blocking cap C109. Filter caps C112, C113 to see if they have low resistance reading.
What is the P/N of U108, 109?

[imp]

Re: Burnt components in USB DAC + help in identifying

Good morning,

I´ve checked the components you mentioned and the all seem OK. There are no shorts and the capacitors measure a reasonable value (given I haven´t anything to compare to).

Also attached another photo for more information on U108 and U109 + the USB input board.

[tom66]

Re: Burnt components in USB DAC + help in identifying

Those inductors are Coilcraft LPS3015 - http://www.coilcraft.com/lps3015.cfm

I know because I've used them in a design before, very nice inductors, small and high inductance, but a bit pricey.

[imp]

Re: Burnt components in USB DAC + help in identifying

There seem to be a short between two of the pins U107 where the heated area is. I´ll order a replacement from Digikey or RS Components and change it, hope it makes some difference

[ben7]

Re: Burnt components in USB DAC + help in identifying

There seem to be a short between two of the pins U107 where the heated area is. I´ll order a replacement from Digikey or RS Components and change it, hope it makes some difference

Um, which two pins is it?

[imp]

Re: Burnt components in USB DAC + help in identifying

Um, which two pins is it?

Between the top right pin and the one just below (referring to the last attached image).

[ben7]

Re: Burnt components in USB DAC + help in identifying

Between the top right pin and the one just below (referring to the last attached image).

Ok, indeed one of the mosfets inside the ZXMHC3A01T8 has gone short G-D.

Time to order a replacement.

[imp]

Re: Burnt components in USB DAC + help in identifying

Yup I´ll let you know the result after I changed the IC.

[imp]

Re: Burnt components in USB DAC + help in identifying

Changed the IC a couple of days ago, unfortunately it didn´t make it work

The IC still gets VERY hot (I switch the power off in less than five sec so it won´t get ruined) so I suspect something else is shorting it out. I´m quite certain that all the surrounding components are correct but the two small transformers may the problem, however, I can´t measure them properly in circuit and if I desolder them I might ruin them ....

[ben7]

Re: Burnt components in USB DAC + help in identifying

Changed the IC a couple of days ago, unfortunately it didn´t make it work

The IC still gets VERY hot (I switch the power off in less than five sec so it won´t get ruined) so I suspect something else is shorting it out. I´m quite certain that all the surrounding components are correct but the two small transformers may the problem, however, I can´t measure them properly in circuit and if I desolder them I might ruin them ....

The smps control chip might be fried too

[b700029]

Re: Burnt components in USB DAC + help in identifying

Remove U107 and measure the resistance between pin 7 and ground. There might be something shorted in the output that's causing it to heat up.

[imp]

Re: Burnt components in USB DAC + help in identifying

Remove U107 and measure the resistance between pin 7 and ground. There might be something shorted in the output that's causing it to heat up.

Tnx, I will try that