Question Need help to find diode component on hard disk circuit board

Apr 13, 2020
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Hello,
My old (0A28613, 0A52026 year 2007) hitachi 160 gb hard disk doesn't power up anymore. After reading a lot about these issues, one common cause seems to be a burnt diode. I opened up the board but I couldn't find the diode. Could somebody point me in the right direction?

Here is an image: HDD
Thanks!
 
Last edited:
Apr 13, 2020
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I think that old drive has a Fuse and not a diode, see if there is a component marked F1
Yes, I did find the fuse (guess it's the blue-ish part, labeled with either N or Z or 2) Do you have any hints what components to test to figure out why my old drive isn't even spinning?
Thank you!
 

popatim

Titan
Moderator
Motor controller was common on those if I remember correctly if the fuses tested good. You probably would be better off with swapping the board they trying to replace the MC. You'll need to transfer the eprom chip(s) over to the new board as well (U4/U5 or maybe it was u5/u6...old age). Note that there may be one or two chips so match the number or chips with your replacement board. Ie if your's has only 1chip then don't get a replacement that has two.

Most places that sell the boards do free eprom transfers too the last time I used one
 
A board swap in this model is a bit more difficult. Hitachi PCBs of that era typically had a ROM chip and a separate NVRAM chip. In your case U6 contains the NVRAM but the ROM code is embedded within the OA50489 Hitachi/Renesas MCU chip. IIUC, you must ensure that the code version in the NVRAM matches the code version in the MCU. I would confer with your PCB supplier, should you choose to go down this path.

As for voltage test points, I would measure the voltages at the fuse (F1), the 4R7 inductor, and the capacitors adjacent to MOSFETs Q2 and Q1. I expect you should see +5V, +1.2V and +3.3V.
 
Apr 13, 2020
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A board swap in this model is a bit more difficult. Hitachi PCBs of that era typically had a ROM chip and a separate NVRAM chip. In your case U6 contains the NVRAM but the ROM code is embedded within the OA50489 Hitachi/Renesas MCU chip. IIUC, you must ensure that the code version in the NVRAM matches the code version in the MCU. I would confer with your PCB supplier, should you choose to go down this path.

As for voltage test points, I would measure the voltages at the fuse (F1), the 4R7 inductor, and the capacitors adjacent to MOSFETs Q2 and Q1. I expect you should see +5V, +1.2V and +3.3V.
Do you mean measure these components in/out values while plugged in?
How would I get the information on whether it would be enough to transfer just the RAM for this particular model?
 
Apr 13, 2020
4
0
10
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A board swap in this model is a bit more difficult. Hitachi PCBs of that era typically had a ROM chip and a separate NVRAM chip. In your case U6 contains the NVRAM but the ROM code is embedded within the OA50489 Hitachi/Renesas MCU chip. IIUC, you must ensure that the code version in the NVRAM matches the code version in the MCU. I would confer with your PCB supplier, should you choose to go down this path.
I think I'm just going to order a replacement. I found the exact pcb board here. They even replace the ROM chip of the board. I didn't understand what you meant with NVRAM chip though. Is that something I would have to do myself?
Thank you for your help!
 
Your questions suggest that your are not comfortable with voltage measurements.

As for your questions regarding ROM and NVRAM, see this PCB:

https://sep.yimg.com/ay/yhst-14437584971410/hds721010kla330-0a29689-0a29470-0a29636-0a33863-ba2469-oa29689-oa29636-oa29470-3-5-sata-hitachi-circuit-board-fw-4.gif

It has a ROM at U5 and an NVRAM at U7. The supplier incorrectly refers to U7 as the "BIOS IC". Your PCB has an NVRAM chip, but no ROM. The NVRAM needs to be transferred to your replacement PCB. Hopefully that will be sufficient.

Good luck.
 

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