Question: 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!
Answer: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.