HI,
I have a WD800JB hard drive that is not being recognized by BIOS. It doesn’t seem to be spinning and has not be dropped
or had any improper voltages applied.
What Diodes and/or resistors should I check. Where are they located? I have a picture of the board here:
http://i1218.photobucket.com/albums/dd414/gps_ggek/IMG_5817.jpg
I also have a exact same model number/firmware version of the bad drive. I have been told I can try swapping boards but most likely the U12 ROM chip would need to be swapped also. I’d rather cut componets on the bad board rather than try to swap a 8 pin surface mounted ROM chip. If I swapped boards would this cause any further damage?
Thanks for any suggestions!
Your board doesn’t appear to have any protection diodes. 
If you have a multimeter and wish to check some voltages, then look for voltage activity at the motor terminals soon after power-on. This will tell you if the motor controller is attempting to spin up the motor.
Next, measure the voltages on the each of the pins of U6. That’s a multiple-output linear regulator. Use the ground at the Molex power connector as your reference.
Also measure the pins of Q4. I suspect that’s the pass transistor for an additional linear regulator.
Measure the supply voltages at pin 8 of the 8-pin flash memory IC at U12, and pin 1 of the SDRAM at U4. Also measure the voltages at the jumper pins. This will be the Vio supply.
Lastly, measure the voltages at the 20-pin preamp connector, J1. I believe the supply pins for the preamp (+5V, ground and -5V?) will be the heavier pads in the vicinity of pins 1-6.
Please be careful when taking measurements, as a slip of the probes will be disastrous.
Hi fzabkar,
Thanks for letting me know there are no protection diodes on this board, that’s one less thing to check
First, I do have a multimeter. Can I safely unscrew the board from the drive and just apply power via a spare molex connector from my computers’ Power Supply? Does the IDE connector need to be connected also?
Yes, power the board up on its own, with just the Molex power connector.
Hi fzabkar,
Since I don’t have any TVS Diodes on this board, and since I had an identical HD model and known good board, I took both the good drive and bad drive to a repair place. I asked them to swap the U12 ROM chips and put the “good” board with the ROM from the “bad” drive and see if that will fix the drive.
After doing this, the drive spun up but in BIOS was recognized as a “WDC ROM MODEL - MAMMOTH 13.03G13”.
The person at the repair place said that the preamp chip inside the hard drive is bad. The cost to repair then is far greater than the data, so I’m at a dead end.
Does this make sense to you?
Yes, that makes sense. After the drive spins up, it attempts to read the System Area on the platters. That’s where the runtime firmware is stored. If it is unable to do so, then AIUI it identifies itself with an alias that is stored in the U12 “ROM”, in this case “MAMMOTH”.
