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 Post subject: Need Help to ID diodes and readings
PostPosted: June 19th, 2022, 21:38 
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Joined: June 19th, 2022, 11:55
Posts: 6
Location: United States
I tried to post this earlier today, but I do not see it anywhere. I hope I am not duplicating. I made a rookie mistake when I replaced my power supply. I replaced the PS but not the cables and I toasted 14 4TB disks in my UNRAID server. Live and Learn! From doing some research here and other sites, I am hoping to remove the toasted Diodes and then get power to the drives so I can copy all the data to New HDDs that I have already bought.
I am just a little confused on which diode(s) and what the multimeter readings are that point out the bad diode(s). (6) of my HDDs are WD RED and have PCBs that are 2060-8000055—002 REV1P. I will try to upload pics of the board. Here are the readings on the Diodes I checked. Hopefully someone can point me in the right direction to go.
ORANGE circle readings: Red lead---- OL--- Black lead THEN Black lead --- .120--- Red lead
BLUE circle readings: : Red lead .868--- Black lead THEN Black lead---.119--- Red lead
RED triangle readings: Red lead---- .115--- Black lead THEN Black lead --- OL--- Red lead
YELLOW star readings: Red lead----OL--- Black lead THEN Black lead --- .115--- Red lead


Attachments:
PCB1 marked.jpg
PCB1 marked.jpg [ 758.29 KiB | Viewed 4095 times ]
PICT0002.jpg
PICT0002.jpg [ 6.12 MiB | Viewed 4095 times ]
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 Post subject: Re: Need Help to ID diodes and readings
PostPosted: June 21st, 2022, 12:42 
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Joined: September 8th, 2009, 18:21
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Location: Australia
Measure the two fuses marked "S". The one on the right will most probably be open circuit.

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 Post subject: Re: Need Help to ID diodes and readings
PostPosted: June 21st, 2022, 19:25 
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Joined: June 19th, 2022, 11:55
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Location: United States
Thank you for the response. Not good with a meter, so here is what I got. Meter on Ohms chip to the right I got OL. Chip to left I got 0.00. Set to diiode chip to right = OL both ways, chip to left = 0.00both ways, Set to BEEP, chip to right = OL no beep both ways, chip to left = BEEP 0.4 both ways. My guess is that you are right with the chip to the right being bad. So, do I remove it or solder over it in a "bloob" so the ends are joined? I have a digital microscope and hot tweezers.


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 Post subject: Re: Need Help to ID diodes and readings
PostPosted: June 22nd, 2022, 0:01 
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Location: Australia
Flow a blob of solder over the fuse. Assuming there are no other problems, you should be OK.

You could take some additional measurements to give you added confidence, but I would need to see the complete PCB.

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 Post subject: Re: Need Help to ID diodes and readings
PostPosted: June 23rd, 2022, 8:24 
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Joined: June 19th, 2022, 11:55
Posts: 6
Location: United States
Thank you for the info. I am looking for all the help I can get. I will upload pics of my PCBs. I do have my meter readings from the same 4 points as the 1st post on all these PCBs if I need to add them to a post.


Attachments:
Disk 8.jpg
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Disk 7.jpg
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Disk 6.jpg
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Disk 5.jpg
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Disk 4.jpg
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Disk 3.jpg
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Disk 2.jpg
Disk 2.jpg [ 681.81 KiB | Viewed 3952 times ]
Disk 1.jpg
Disk 1.jpg [ 712.06 KiB | Viewed 3952 times ]
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 Post subject: Re: Need Help to ID diodes and readings
PostPosted: June 23rd, 2022, 9:00 
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Joined: November 7th, 2020, 5:31
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Location: The_UK
Hope you labelled the drives and PCBs properly. 6 & 4 have let the magic smoke out so you're past diode/fuse replacement stage for those .

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 Post subject: Re: Need Help to ID diodes and readings
PostPosted: June 23rd, 2022, 9:25 
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Joined: June 19th, 2022, 11:55
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Location: United States
Yes, all drives and PCBs labeled/paired. I missed those 2 in my initial eval, when I took the pics and zoomed in I had my "oh crap" moment. I will be buying donor replacements for those 2. Thank you for your observations.


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 Post subject: Re: Need Help to ID diodes and readings
PostPosted: June 23rd, 2022, 14:51 
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Measure the resistances of the TVS diodes, fuses and zero-ohm resistors.

Measure the resistance between ground and each of the Vx test points. These are the onboard supply voltages. One or more of these test points may be the grounded end of the inductor in the negative supply for the preamp, in which case the resistance will be 0.0 ohms. This is normal.

Measure the resistances between ground and each of the two test points in the "piezo" photo clips. I could be wrong, but I suspect that these are the positive and negative supplies for the microactuator on the headstack.

Measure the resistances between ground and the two +/-5V HDA pads. These are the supply voltages for the preamp on the headstack. Repeat this with the PCB on the drive. You will need to find the appropriate test points on the other side of the PCB by following the plated thruholes.

Any screw hole can be your ground reference.

I suspect that drives 1, 2, 3, 7 and 8 have survived. Drives 4 and 6 have dead motor controllers, and I fear that drive 5 may also have a dead controller, even though there is no visible damage. This is because the "protection" circuitry is cr@p. Every time I see this stupid design I feel like bashing the designer's head with a cricket bat.

There is a very real possibility that the preamps in drives 4, 5 and 6 have been damaged. Your resistance measurements will tell us more.


Attachments:
Drives_7_8_regs.jpg
Drives_7_8_regs.jpg [ 149.87 KiB | Viewed 3908 times ]
Drives_7_8_piezo.jpg
Drives_7_8_piezo.jpg [ 59.52 KiB | Viewed 3908 times ]
Drives_7_8_preamp.jpg
Drives_7_8_preamp.jpg [ 64.59 KiB | Viewed 3908 times ]
Drives_7_8_TVS_resistor.jpg
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Drives_1_2_3_regs.jpg
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Drives_1_2_3_preamp.jpg
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Drives_1_2_3_TVS_fuse.jpg
Drives_1_2_3_TVS_fuse.jpg [ 141.06 KiB | Viewed 3908 times ]

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 Post subject: Re: Need Help to ID diodes and readings
PostPosted: June 23rd, 2022, 14:55 
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Here are the pics for the dodgy drives.

You should remove any shorted TVS diodes before taking the other resistance measurements. This is to prevent the short from influencing the other results.


Attachments:
Drives_7_8_regs.jpg
Drives_7_8_regs.jpg [ 149.87 KiB | Viewed 3908 times ]
Drives_4_5_6_piezo.jpg
Drives_4_5_6_piezo.jpg [ 71.04 KiB | Viewed 3908 times ]
Drives_4_5_6_preamp.jpg
Drives_4_5_6_preamp.jpg [ 70.37 KiB | Viewed 3908 times ]
Drives_4_5_6_TVS_resistor.jpg
Drives_4_5_6_TVS_resistor.jpg [ 132.25 KiB | Viewed 3908 times ]

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