Can someone please confirm for me where NVRAM is located on this model? Embedded in MCU?

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bottom right
US406C
ROM+NVRAM

Judging by the pcb layout, my guess would be botom right near the screw hole.

Rgds

Ahhh, too late

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LE25FU406B, Sanyo, 4M-bit (512Kx8), 2.3V - 3.6V, Serial Flash Memory:
https://media.digikey.com/pdf/Data%20Sheets/ON%20Semiconductor%20PDFs/LE25FU406B.pdf
http://semicon.sanyo.com/en/ds_e/ENA1066E.pdf
http://pdf.datasheetarchive.com/indexerfiles/Datasheets-SW5/DSASW0080400.pdf

http://www.users.on.net/~fzabkar/Datasheets/DATAURLS.HTM

TCV7104FN, Toshiba, buck DC-DC converter, 2.7V - 5.5 Vin, marking V104, SON-8:
https://np.micro-semiconductor.hk/datasheet/07-TCV7104FN(TE85L,F).pdf

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Drive has a damaged PCB so I've already moved that IC in question to compatible donor PCB. The 8 pin IC bottom right of the PCB pic. Problem is, patient won't spin with donor PCB and patient ROM.

Drive does come DRD DSC and reports correct S/N, but will not spin. Patient with donor PCB and donor ROM does spin, ID's with donor S/N but obviously no LBA access.

Trying to figure out why patient with donor PCB and patient ROM will not spin. Thought perhaps NVRAM was situated elsewhere and wasn't part of ROM IC?

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i recall like these were built with 2 different spindle controllers and they are not compatible, so check the numbers on it on both pcbs.

pepe

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The two different motor controllers appear to be TLS2604 and R42AAJ.

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A backup a day keeps DR away.

Thanks fzabkar and pepe. My first donor PCB did indeed have a different motor controller. Patient was TLS2604 and donor was R42AAJ. Wrote ROM to another donor PCB with matching TLS2604 and case solved. Seems I was trying to overcomplicate this case when it was just a matter of matching PCB properly. Thanks guys.

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pepe

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This supplier ...

https://www.aliexpress.com/item/32789772849.html
https://ae01.alicdn.com/kf/HTB1u0b5PXXXXXXzaFXXq6xXFXXXD/HDD-PCB-for-Hitich-Logic-Board-Board-number-420-0A90415-01-Main-Controller-IC-88i9305-NDB2.jpg

... claims that "both [HDD Motor Combo] IC is compatible with each other", but they also identify the Marvell MCU as the "BIOS chip".

????

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A backup a day keeps DR away.

It might be interesting to compare the donor and patient ROMs to see whether the difference is in the ROM code or the NVRAM.

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A backup a day keeps DR away.

It would be interesting but also a tedious task to find the differences responsible for handling the spindle controller... and what would we do with the info?
It would be more interesting to get a drive read with the other type of pcb, with the donor fw, and this is something less complicated and time consuming.

pepe

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I was thinking that one could transfer the NVRAM from patient to donor rather than ROM + NVRAM, assuming that the differences were in the ROM code.

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A backup a day keeps DR away.

that doesn't work on its own.

pepe

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I understand, but PC3K users know how to modify an NVRAM to make it compatible with a donor ROM, do they not?

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A backup a day keeps DR away.

It is not a question of being a PC3k user IMO, some people know, but the most doesn't, probably.

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