Not so long ago I had a hideous noise coming from a cooling case fan on one of my PC’s. It was powered by the usual 4 wire (Y 2xBk R) cable but used an in-line splitter which also powered the WD20 hard drive. Rather than go to menial effort of getting my daughter to get off the PC, I “hot” disconnected the fan from the harness and reconnected the hard drive but possibly did do upside down (i didn’t realise the hard drive was on the this particular harness until later). This shut the whole PC down and I had to do a full power off (disconnect then reconnect power) restart. It powered up fine and I thought I’d gotten away with it. As it transpires I hadn’t, the aforementioned hard drive wasn’t being seen at all and all my data and downloads which were stored on it. I quick look see suggested it wasn’t spinning (it’s a slave btw so everything else worked fine).
I connected the hard drive into another PC to make sure it wasnt the mother board and this confirmed the drive wasn’t spinning.
A good bit of reading later I now know that it is most likely the PCB is away. Moreover it’s most likely that a TVS diode had popped to protect the drive. I have to say that my PCB looks in really good condition, no obvious burns or blackenings. Nevertheless I purchased a replacement board (matched etching 2060-771698-xxx) from an outfit in hong kong and it has now arrived.
They state the following detail regarding the board:
Board Number: 2060-771698-004
Main Controller IC: 88i9146-TFJ2
HDD Motor Combo IC: L7251 3.1
Their websites states that I need to swap out the bios chip (U12) and possibly the IC (U5). I have a local specialist who will “rework” the board for me and replace the two surface mounted components.
Hopefully all of the above is the correct procedure for getting a working replacement PCB for my hard drive- I only want it to work as long as is necessary to get a couple of gig of family photos off of it. The rest can go to silicone heaven for all I care.
Right then, the second part of my question…
There is no point fo going to the effort of having thechips swapped out if the replacement board doesn’t work (it’s obviously second hand but I only have their word for it that it is “tested” before despatch). Accordingly I want to check the obvious things and need someone to say “aye” or “naw” to using the replacement board.
I think I have to check diode D3 and (what I assume to be) the TVS diode which doesnt appear to have a reference but is alongside R64. I have assumed this is D4.
^^^ OLD PCB
^^^ NEW PCB
I checked each using my ohm meter and continuity meter (buzzer) on both forward (black probe to the stripe end) and reverse(red probe to stripe end) as follows:
I used a FLUKE 77 mutlimeter.
D3 = 8AE 18A M
D4 (TVS Diode - I assume) = 6BG 18A M
Old Board D3 forwards 280ohms (continuity = short buzz then .162 reading)
Old Board D3 backwards 218ohms (continuity = short buzz then .151 reading)
Old Board D4 forwards 0.3Mohms (continuity = short buzz then .534 reading)
Old Board D4 backwards 0.3Mohms (continuity = short buzz then 1.4 reading)
New Board D3 forwards 3000ohms (continuity = no buzz / .0L reading)
New Board D3 backwards 20ohms (continuity = continuous buzz then .005 reading)
New Board D4 forwards 0.3Mohms (continuity = short buzz then .536 reading)
New Board D4 backwards 0.3Mohms (continuity = no buzz / 1.4 reading)
Does this make sense?
Thanks for any help I can get since I want to know where I stand before Wednesday when I take these board for their rework.
Out of interest, what is the story regarding disconnecting the diode(s) to make the drive work?
And, also out of interest, if it’s the TVS diode which is normally popped then why swap out the BIOS and IC if all that needs swapped is the diode?
