Need Help to ID diodes and readings

[Autohaul58]

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

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[fzabkar]

Measure the two fuses marked "S". The one on the right will most probably be open circuit.

[Autohaul58]

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.

[fzabkar]

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.

[Autohaul58]

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.

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[Lardman]

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 .

[Autohaul58]

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.

[fzabkar]

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 (149.87 KiB) Viewed 5042 times

Drives_7_8_piezo.jpg (59.52 KiB) Viewed 5042 times

Drives_7_8_preamp.jpg (64.59 KiB) Viewed 5042 times

Drives_1_2_3_regs.jpg (138.63 KiB) Viewed 5042 times

Drives_1_2_3_preamp.jpg (60.43 KiB) Viewed 5042 times

Drives_1_2_3_TVS_fuse.jpg (141.06 KiB) Viewed 5042 times

[fzabkar]

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.

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Drives_7_8_regs.jpg (149.87 KiB) Viewed 5042 times

Drives_4_5_6_piezo.jpg (71.04 KiB) Viewed 5042 times

Drives_4_5_6_preamp.jpg (70.37 KiB) Viewed 5042 times