EEVblog Electronics Community Forum
Electronics => Repair => Topic started by: astrojucar on August 05, 2021, 09:31:51 am
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It is part of an HDMI over Cat-6 receiver. It is shorted and gets REALLY hot.
I haven't been able to find anything on google.
I am lost, do any of you know by any chance what that is and how to replace it?
Thanks! ;)
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The only reference I could find in a SMD codebok (http://caxapa.ru/thumbs/588912/smd-codes.pdf (http://caxapa.ru/thumbs/588912/smd-codes.pdf)) is:
SMDcode Type Function Short description Case Pin. Mnf.
ABDO MAX6306UK31D3-T CMOS-IC Voltage Detector 3,1V, -MR, -Reset ODO, 140ms SOT-23-5 28ek - Max
(Of course not sure if this is the right part. )
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Thanks! I think it is a 1.2V regulator because the main chip uses that voltage.
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It appears to be an adjustable step-down converter.
1 = Vcc
2 = Gnd
3 = Lx
4 = N/C ?
5 = FB
If you can measure the two resistors at the FB pin (R8 & R9), then we will be able to work out the FB voltage. That will then help us to search for suitable replacements.
Have you measured the resistance between the coil and ground? That will tell us if the load is shorted rather than the IC itself.
What are the markings on U1? Perhaps it is manufactured by the same company?
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Could be SY8008B
http://www.sunnyqi.com/upLoad/product/month_1306/SY8008.pdf (http://www.sunnyqi.com/upLoad/product/month_1306/SY8008.pdf)
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Definitely a switching regulator.
I'd check those 3 ceramic capacitors on the input, make sure they're not shorted . The smallest looks much darker than the others, which could be a sign of being shorted, but could also be just a different composition. Do the same on the output, it's easy to check.
Yeah, resistors will tell you the output voltage. Most likely the chip has a 0.6v voltage reference, or maybe 0.8v... less likely it will be a more generic 1.25v reference voltage
I don't know the formula off the top of my head...it's something like reference voltage x ( 1 + R1/R2) or something like that. You can pick any high frequency synchronous rectifier switching regulator off digikey or mouser or whatever and look in datasheet for the formula.
It's not that SY8008 chip, because there doesn't seem to be an ENABLE pin and the inductor is obviously connected to other pin, not like in the pdf.
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Could be SY8008B
http://www.sunnyqi.com/upLoad/product/month_1306/SY8008.pdf (http://www.sunnyqi.com/upLoad/product/month_1306/SY8008.pdf)
That would be a possibility only if pins 1 and 4 were connected underneath the package.
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Pretty sure it's SY8008BAAC. 1 and 4 are almost certainly connected underneath, and there may be a via or two under there too.
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I didn’t say that it must be SY8008B because the inductor L2 is 2.2uH and in some schematics I found it is 4.7uH. Later I realized that SY8008 and RT8008 are pin-to-pin compatible, and a 2.2uH inductor used in typical application of RT8008.
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RT8008 has different marking. Marking of OP's part matches SY8008BAAC.
As for the inductor, the datasheet for the SY8008 characterises it with a 2.2u inductor.
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RT8008 has different marking. Marking of OP's part matches SY8008BAAC.
As for the inductor, the datasheet for the SY8008 characterises it with a 2.2u inductor.
I know they have different markings, I'm just saying that they are pin-to-pin compatible, so they should have the same peripheral components.
Components in the schematics in the datasheet of SY8008 have no values. After reading your post, I found that the inductor's value is mentioned in the electrical characteristics table.
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Shanghai Belling BL3406B-1.2V (https://pdf1.alldatasheet.com/datasheet-pdf/view/469736/BELLING/BL3406B-1.2V.html) But the aforementioned Sy8008 will fit the bill as well.