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SP A55 4TB
http://forum.hddguru.com/viewtopic.php?f=10&t=45749		 Page 1 of 1
Author:  Lardman [ December 3rd, 2025, 14:05 ]
Post subject:  SP A55 4TB
Trying to clear the desk before the holidays.

This came in with an obvious blown fuse on the main 5v VCC, but with the fuse removed and everything cleaned up (I can see no other visible damage to ics or pcb) there's still an a hard 0.1 ohm (test leads value) short to ground after the fuse. Injecting, it pulls 3amps at 1.5v but there is absolutely nothing showing on thermals other than the injection leads.

Needless to say I've not been able to find another drive with the same pcb to use as a donor or to get decent measurements from.

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Author:  fzabkar [ December 3rd, 2025, 16:14 ]
Post subject:  Re: SP A55 4TB
I see 3 buck converters. Check for shorts between ground and each of the inductors. If they are OK, then remove each buck in turn until the short is cleared.
Author:  fzabkar [ December 3rd, 2025, 17:13 ]
Post subject:  Re: SP A55 4TB
I found this photo:

https://img.mydigit.cn/forum/202409/06/232535x1wr2ofkcz4zo6zz.jpg

Your 10-pin buck seems to be equivalent to this:

https://datasheet4u.com/pdf-down/J/W/5/JW5255A-JoulWatt.pdf
Author:  Lardman [ December 4th, 2025, 8:29 ]
Post subject:  Re: SP A55 4TB
Already pulled them, even with the three removed the short remains somewhere between the fuse and the bucks , pre and post appears to be okay.
Author:  Lardman [ December 4th, 2025, 9:39 ]
Post subject:  Re: SP A55 4TB
I found it... It was one of the 2 caps right next to the ground connection I was using which is why I couldn't find see any heat on the thermals it's masked by the hook up leads. The screw holes on these aren't common ground. As always Franc many thanks for assist and reminder to do things methodically and not to be a tool. :oops:
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