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 Post subject: Re: PCB swap on a WD10EAVS
PostPosted: January 12th, 2018, 16:20 
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If the damaged drive have a PCB without ROM chip (ROM EMBEDED ON MCU) then you could use tools like the following ones to rebuild the ROM by reading the COPY on the SA and write it back to the donnor (new) PCB :

WDMarvel :

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SeDiv :

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WDR :

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For HRT 3 you would need to READ SA then re-create ROM with HEX editor by manual way explained here - http://www.hddoracle.com/viewtopic.php?f=86&t=1429 and then write it to PCB this way :

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HRT 5 UDMA can DECODE ROYL ROM (or even "older" MARVELL based) but you would still have to use the manual method to rebuild ROM by reading SA first :

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When i do have to rebuild ROM i allways use HRT card + WDMarvel tool as i think it's the easy way for me. You can do it as well without any hardware card as WDMarvel is SOFTWARE ONLY.

What i do is to READ SA first and then use automatic WDMarvel method and then check ROM MODULES with HEX EDITOR and if they look ok (not empty) i write ROM to PCB but make sure first that ROM size is correct by backing up donor PCB ROM first and comparing ROM size with image of ROM (re-build) that you are going to write.

It's very easy if you know what you are doing but can be very complex if you don't understand (fully) what you are doing and you might brick the PCB if you write wrong code to it or if your system does interfeer with the PCB while you are writting ROM (if you don't have hardware based tools like MRT, PC-3000, HRT, whatever ....) This is another risk of software only tools.

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 Post subject: Re: PCB swap on a WD10EAVS
PostPosted: March 8th, 2018, 13:19 
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Joined: November 22nd, 2017, 21:47
Posts: 142
Location: France
I got an update from the owner of the damaged WD10EAVS : he simply wrote that the PCB swap didn't work – well, as I expected.
I'm asking him questions based on earlier input I got here (did he just swap the boards or attempt something with the TVS diods or the MCU ? what kind of noises did he hear ?...). Depending on the replies I may try to assist him remotely.

Quote:
The damaged PCB and your PCB might or might not have the external chip. You have to check that out on the PCB. even if they have the same model and PCB version there are the chance that one have external ROM and the other have internal one. The only way to be sure is to check.

You mean, even if the unit I sold didn't have an external ROM chip, if his damaged one does have such a chip, it could be soldered to the replacement board and the assembly would work ? In that case, wouldn't there be a conflict between the ROM information in the transposed chip, and the native ROM inside the MCU (since the replacement board definitely does not have an external chip in U12) ?

Quote:
Only if you are extremely lucky will the PCBs work without swapping the ROM chip or write the native ROM code on the new PCB as there will be adaptives on ROM modules.

I got that part, from the begining actually, but apparently he didn't, although I stated it repeatedly (that it would be very unlikely to work right away with a simple PCB swap).

Quote:
Owner can check TVS/DIODES but if the drive is not shorting the PSU and shutting the system down then it will have other issues like open resistor and there will be no short-circuit.

I asked again, but he didn't mention any kind of shutdown.
Question : it only shuts down the PSU if the HDD is connected internally, not if connected through an external enclosure or similar, right ? (Seems obvious but... not much should be taken as “obvious” when it comes to HDDs !)

Quote:
Pre-amp might still be damaged or heads might still be damaged even if the drive spins with a non-native PCB. What we can assume is that the pre-amp at least is not shorted otherwise it would not make the drive spin.

Head damage would always result in a clicking pattern, right ? Or not necessarily ?

Quote:
Does the drive clicks ? Does the drive makes a noise of heads reading something ?

I asked, waiting for the reply.

Quote:
If the ROM is inside MCU there will exist a copy of the ROM on SA (platter) so one would replace the PCB with compatible one and use some sort of WD firmware tool to read ROM copy from SA and write it to PCB.

Probably irrelevant here, but I asked again if there's a chip in U12 on his damaged unit.

Quote:
If the damaged drive have a PCB without ROM chip (ROM EMBEDED ON MCU) then you could use tools like the following ones to rebuild the ROM by reading the COPY on the SA and write it back to the donnor (new) PCB

Well, before I start to delve deeper, which among those tools can be had for free, if any, even if that's a demo version which would still allow that specific procedure ? Is WDMarvel demo version enough ? From what I could gather, all the others are really expensive tools.

Quote:
It's very easy if you know what you are doing but can be very complex if you don't understand (fully) what you are doing and you might brick the PCB if you write wrong code to it or if your system does interfeer with the PCB while you are writting ROM (if you don't have hardware based tools like MRT, PC-3000, HRT, whatever ....) This is another risk of software only tools.

Well, that's another situation where it would be adviseable to do a lot of thorough testing before attempting the actual procedure, I guess ! :) What kind of test can I do here ? Take a “guinea pig” WD HDD (I have an empty 250GB IDE one which I found in a damaged standalone video recorder), backup its ROM, then replace it with garbage, then verify that it's no longer functional, then write it back, then verify that it's functional again ?
In any case, I'll remind him that he can bring this to a DR lab, for that kind of failure I suppose that it would be way cheaper than for a mechanical failure (for an electronic failure the one in my area asks 190 to 350€ with the standard 8-15 days delay).
Are there means to prevent the system from interfering with the PCB ? And what exactly do you mean by “interfering” ? By definition ROM should be read-only, right ? (I mean, during the regular operation.)


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 Post subject: Re: PCB swap on a WD10EAVS
PostPosted: March 8th, 2018, 18:10 
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If the pcb that you sold DOESN'T HAVE a ROM chip you can solder the ROM from the other PCB and your PCB will still read the internal ROM. For you to make it READ and WRITE to the external ROM chip you need to solder some resistors on the PCB as well. This instructs the MCU to read from external ROM instead of internal. It would be simpler to read ROM with external programmer and write it to the PCB by Firmware tool.

Regarding this :

Quote:
backup its ROM, then replace it with garbage, then verify that it's no longer functional, then write it back, then verify that it's functional again ?


Don't do it. As soon as you reach the part to "no longer functional" unless it does have extrenal ROM chip that you can re-programm with external programmer or you have a tool that can unbrick the pcb by TTL (and writting correct ROM) you will kill the PCB and you will NOT be able to write ROM back....

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 Post subject: Re: PCB swap on a WD10EAVS
PostPosted: March 9th, 2018, 9:51 
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Joined: November 22nd, 2017, 21:47
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Quote:
It would be simpler to read ROM with external programmer and write it to the PCB by Firmware tool.

In that case, it would read from the (hypothetical) external ROM chip on PCB A, and write it to the MCU of PCB B (which has no external ROM), correct ?

Quote:
Don't do it. As soon as you reach the part to "no longer functional" unless it does have extrenal ROM chip that you can re-programm with external programmer or you have a tool that can unbrick the pcb by TTL (and writting correct ROM) you will kill the PCB and you will NOT be able to write ROM back....

Alright, so bad idea, even for testing purposes... Is there something else that can be done to test the tool before a first actual procedure ? (That wouldn't entail purchasing two identical drives, if possible... I do have several pairs of WD HDDs with the same model number – including the two WD6400AAKS mentioned in another thread – but none that are currently “expendable”.)

In this case, I would have to do the procedure twice, ideally : once to (hopefully) make the damaged HDD readable again, and once to write back the original ROM to the replacement PCB, so that the healthy HDD (the one I sold) can be used normally later on. For the second part, it has to be done after the PCB has been put back on its original drive, or it doesn't matter ? In any case, once the correct ROM is written to the PCB, there has to be a power cycle for it to be read and for the HDD to (hopefully) start normally, right ?

Regarding the software tools, WDMarvel's demo version is read-only, so it wouldn't do all that's needed, but there's a one month license for $15, it seems to be the cheapest option for a one-time job (I'll have to be sure that the guy wants me to try the trick – but in any case the acquired knowledge won't be lost, it might prove worthwhile later on). But apparently its scope is more limited than HRT / SeDiv for instance ; which one(s) did you purchase first, and which one(s) would you consider the most powerful and / or most useful in the long run, when dealing with drives from various brands / models ?

EDIT : Oh, and to read from the SA with WDMarvel (or any of these tools), it is not necessary to perform a hot swap ?
In which cases is it necessary to perform a hot swap in order to access the system area ?


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