for example how we can test if any electronics component is in bad condition.

i attach pics from a case to test.
Thanks in advanced.

For this case uaually not the hardware problem.
I use multimeter for test.

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Hi NetworkPC3000!
thanks for your help

but i would like advices about how to use multimeter, in this cases.
What points to test, correct values in those points, and so on..

can you help me with?

For this one it's worth checking green resistor with "02" on it from the bottom view.

P.S.
What's the vendor / model of this flash drive? Toshiba controller with Toshiba memory chips is quite an infrequent combination.

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The "green resistor" appears to be a polyswitch. That's a resettable fuse. It appears to be rated for 200mA.

http://pdf.datasheetarchive.com/indexer ... 070002.pdf

I would also measure the voltage across the 3.3V filter capacitor for the NAND flash. That would be generated by the controller.

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Hi, I concur with previous posters that not frequently a component issue. But I have seen quite a few drives with components bad.

In order of components that I have seen failed are:

-Resistors, but these days rare, mainly in older ones.
-Fuses, though these are fairly uncommon, instead would be a resistor that doesn't resist much..
-XTAL or Crystal Oscillator, I keep a variety of flash drives and swap them out for one from a working drive instead of actually testing them. Most common to "go" are the (older) round canister type.

More common is bent, broken, mutilated, crushed, washed and generaly abused drives.

Better to have a fairly quick look, and if no obvious signs of damage/failure then get straight into chip off recovery.

Otherwise you spend too much time

I can't imagine it ever happening, but what would be the symptom of an open USB reference resistor (I'm not sure if I have identified it correctly)?

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Symptom of faulty resistor has been windows saying USB device not recognised, LED blowing controller getting hot to Flash Drive not working at all. There were some tutorials(as in "how to REALLY kill your USB") where they say to bridge a resistor with tweezers. I assume this is when a resistor or fuse blows and would work in a small percentage of cases.

Personally I don't think it is useful timewise to look for circuit problems, unless you already are good with electronic troubleshooting, such as someone like Franc that has an understanding of different circuits, their function and what role each part plays.. With most part sizes being at least 0805 and 0603 and many newer ones being even 0402, de-soldering them to check isn't really viable. I don't think checking in circuit is viable either on these as you would have to know what values you roughly should be seeing

I think you are referring to the low-ohm resistor that is in series with the +5V supply. The component I'm referring to is the 1% reference resistor. Depending on the design, it's value can vary between a few hundred ohms and a few kilohms. It does not carry the supply current.

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A backup a day keeps DR away.

I was speaking generally about any resistor, not answering your specific question I think.

would this resistor be used to adjust the clock signal correctly?

I hope I'm not hijacking this thread (the question appears to be a general one), but here is a reference resistor on a SM3257EN based flash drive that appears not to have been correctly soldered.


Here are both resistors:


I confess that I don't understand it's exact function, but it is specified as a 1% resistor and it is required by the USB section of the controller.

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The OP's "reference resistor" isn't an LED, is it???

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could be, it is in a common place for one

I'm attaching reference circuits for Silicon Motion's SM3255QF and SM3257EN flash controllers.

I notice that there are references to "ROM code mode" and "Debug mode". There is also a TESTN pin which is normally pulled high, but would select some kind of test mode when it is grounded. I don't know if these test/debug modes are data safe, but perhaps they could be useful for diagnostic purposes. Moreover, I would think that most, if not all, flash controllers would have similar features.

FWIW, I notice that the SM3255QF has 300 ohm 1% reference resistor, while the resistor for the SM3257EN is 680 ohm 1%.

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Thanks Dmitri, fzabkar, and HaQue;

I am very happy with your interes in this case.

Thanks Dmitri!

answering your questions:

Vendor: Toshiba
Model: No model
Capacity: 32GB

about "green resistor with "02" " i am with fzabkar. I this is a polyswitch fuse

Hi fzabkar!
thanks for your help

about filter cap, i show you in pic


Important about: Reference resistor; This is not a resistor this is a LED.

I atach pics wit measusres

Hi HaQue!

Thanks for your help too

I think with my respopnses i can response you.

But your advices about common failures in flash drives, and win symptoms are very clever.

if any dound do not worry in ask me.

Thanks anoter time

About the "test mode" pin on the controller. I have noticed that on controllers from many Vendors. There has been no documentation about it. Also it does not appear to be associated with uploading firmware or really anything exciting.

I have thought it may enable JTAG, Serial enable or make some pins different function.

One very interesting project I found today:

https://bitbucket.org/flowswitch/phison


The wiki has some interesting details such as a memory map and some info on commands and interrupts.

Basically I believe this project will allow you to use custom code on the controller of a Flash Drive(PS2251-03). Using CBWCB. I haven't programmed anything serious for USB but I believe this is "Command Block Wrapper Command Block" and you would put in vendor specific commands and arguments/parameters.
The way I understand it is a CBWCB is 16 bytes in size, the first byte(first opcode) specifies the command set or the restrictions on the command set. The second is the command opcode followed by any bytes the command needs as parameters. If it is less than 16 bytes, pad it with 0's

I am not exactly sure just how useful, in the context of debugging a flash drive with an issue, this would be though. But 100 on the cool fun scale.

It would be interesting to use a USB sniffer/debugger and see exactly what VSC's are used in all operations of a drive, and what other opcodes there are hidden away.