Electronics > Repair

Reverse engineer Dallas DS1742W?

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MarkL:
Here's another post comparing a real DS1742W to a fake:

  https://www.eevblog.com/forum/repair/repair-of-tek-tds3014b-need-a-source-for-a-ds1742w-nvram/msg2644260/#msg2644260

And a couple of posts after that one, some photos after I cut into the fake.  The internals look the same as the one zebity posted.

darkstar49:

--- Quote from: MarkL on October 27, 2020, 09:00:29 pm ---Here's another post comparing a real DS1742W to a fake:

  https://www.eevblog.com/forum/repair/repair-of-tek-tds3014b-need-a-source-for-a-ds1742w-nvram/msg2644260/#msg2644260

And a couple of posts after that one, some photos after I cut into the fake.  The internals look the same as the one zebity posted.

--- End quote ---

Is there any technique to check whether a replica/fake DS1742W is functional or not ? What's the culprit with these chinese clones ?
I got one here that I suspect to be a clone, but my programmer is happy with it so far... (although I guess that's not the part that causes trouble...?)

 

james_s:
Well, like I mentioned, mine all had different faults. The only definitive test is to try one in the actual application where it will be used, and even then you don't know how long it will last. My experience suggests that it's mostly a case of just poor build quality using low quality parts. The IC they use might be ok but a cheap battery or a source of electrical leakage (flux residue? leaky decoupling cap? diode leakage?) cause it to discharge.

MarkL:
For clones that aren't downright dead, my pet theory is that the RTC part of the clone chip is drawing way too much current and drains the battery in a matter of maybe months to a year or two.

So it can be programmed normally and will retain the data, and it will keep time.  But only for a while.  Apparently long enough for people to be fooled and leave good feedback.

zebity:
Hi James_s & others,

I agree 100% that people selling chips that don't work is essentially stealing people's money and more importantly wasting their time.

There is only one thing that is important to me and that is whether the chip works or not...

It is easy to verify if the chip works using the "XGecu TL866" programmer.

The programmer comes with a bunch of pre-existing profiles and the one to use for DS1742W is the DS1220 profile, which has the same NVRAM specs as the DS1742W but without the RTC chip.

As the purpose of this thread is about "reverse engineering", I am now going to open up a "genuine" DS1742W-120 and post the outcome of that investigation.

While x-rays are useful they do not provide level of info required to complete reverse engineering work.

I will likely not get this done until weekend but will re-post once completed.

Thanks for all the helpful feedback and information.

Cheers from Oz,

zebity/jwhat/John.

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