SCSI fuse advice (or, how to kill a ThinkPad 800 with a SCSI2SD)

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ClassicHasClass
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SCSI fuse advice (or, how to kill a ThinkPad 800 with a SCSI2SD)

Unread postby ClassicHasClass » Mon Aug 21, 2017 8:06 am

I was antsy about the 2.5" SCSI in my ThinkPad 800 (the original Type 6020 which was never, apparently, sold), so based on reports that it works fine with the TP850, I bought a "PowerBook" SCSI2SD of the same type I currently use in my PowerBook 540c, configured it and installed it. I made sure to insert the pins the same orientation into the carrier board. When I fired the ThinkPad up, it promptly failed to POST with error 0370830. I replaced it with the original drive and got the same error. At this point I may have scared the cat.

Some digging around indicates that this error means the "SCSI circuit breaker is open" ( http://ps-2.kev009.com/eprmhtml/eprm1/h2583.htm ), at least on the TP850. However, the recommended tasks of letting it sit for 15 minutes didn't work, nor did unplugging all the SCSI cables and trying again. Even with no SCSI devices on board (no CD-ROM, no hard disk) it still does this. As usual the IBM service guidance at this point would be to replace the system board, which isn't going to happen.

I disassembled the unit to see if it was actually a fuse (given that this is an earlier model) that opened rather than a circuit breaker, which will be interesting to get back together, but anyway. Once I got the Faraday cage and the video card off I found a couple candidate surface-mount fuses marked F1 and F3, but they're both 2A (which seemed a little high for a SCSI breaker) and continuity testing checks out on both. I can't find any others. F3 seemed like the best candidate since it was nearest to the CD-ROM SCSI port, but it looks like both fuses are still closed. Some of the system board is still covered by the PCMCIA cage and the sound daughtercard, however, so it's possible there are other fuses to find.

Before I make an even bigger mess by trying to get the board completely free and loose from the chassis, anyone got experience with blowing SCSI fuses? Is this something internal to the controller chip itself (which by the way I haven't even identified yet, though I have a couple guesses), or is it usually on the board? What should I be looking for?

I'm also rather alarmed about the SCSI2SD doing that. Could it be that it's pulling too much power from the termination lines?
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Re: SCSI fuse advice (or, how to kill a ThinkPad 800 with a SCSI2SD)

Unread postby ibmfiles » Sun Aug 27, 2017 7:03 pm

Would you be able to take a photo of the area in question?
Maybe it's a diode or something.

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Re: SCSI fuse advice (or, how to kill a ThinkPad 800 with a SCSI2SD)

Unread postby ClassicHasClass » Mon Aug 28, 2017 7:19 pm

I'm pretty sure both are truly fuses, they're marked as such and have "2A" on the top (F1 even has "125V 2A" on the board next to it). It doesn't have the one-way behaviour of a diode and it looks too big for that.

I haven't gotten up the nerve to try to wiggle the other boards off yet.
smit happens.

:Fuel: bigred, 900MHz R16K, 4GB RAM, V12 DCD, 6.5.30
:Indy: indy, 150MHz R4400SC, 256MB RAM, XL24, 6.5.10
:Indigo2IMP: purplehaze, 175MHz R10000, Solid IMPACT
probably posted from Image bruce, Quad 2.5GHz PowerPC 970MP, 16GB RAM, Mac OS X 10.4.11
plus IBM POWER6 p520 * Apple Network Server 500 * RDI PrecisionBook * BeBox * Solbourne S3000 * Commodore 128 * many more...


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