[rescue] Old PSUs & boards: useful to teach self?

Carl R. Friend crfriend at rcn.com
Mon Oct 22 18:30:24 CDT 2007

    On Mon, 22 Oct 2007, William Enestvedt wrote:

>   1. Will opening the PSUs kill me? Is there anything in there to see?

    No, so long as you've waited a decent period of time from when
the PSU was last powered up.  Modern switchers typically store
about 300 VDC across their main capacitors and, needless to say,
getting hit from that will *hurt* (or worse).

    Bleed-down should, in a properly-working PSU (not what you might
find in "rescue gear" mind you) in a couple of minutes, but wisdom
dictates that any large capacitor should be avoided until you're
really sure it's empty.

>   2. What is that one component on a SCSI board that looks like an
> inch-wide doughnut wrapped a few times in heavy copper wire?

    That's likely a choke, and is designed to suppress any RF
energy that might otherwise get out by way of extrernal cabling.
Be careful on this one, though, because torroidal transformers
are also very common in lots of kit.

>   3. Is there anything worth scrounging from this beast in the way I
> get good magnets out of old HDs, or spare RAM? No, the CPUs are long
> long, though the terminal is up in the Data Center acting as a head for
> my V890s & T2000s. :7)

    Quite likely not, unless it's fairly new and you're in need of
filter caps or other power components.  The transformers are more
or less immortal (unlike caps) but can be very application specific.
Mostly, PSUs, if you can't re-use them for other applications, boat-

    Will -- I see you're in the Providence, RI area.  Do think about
stopping by the monthly (third Saturday) Open House at the Retro-
Computing Society of Rhode Island down at Atlantic Mills in the
Olneyville district.  I suspect you'd get a hoot out of it.

| Carl Richard Friend (UNIX Sysadmin)            | West Boylston       |
| Minicomputer Collector / Enthusiast            | Massachusetts, USA  |
| mailto:crfriend at rcn.com                        +---------------------+
| http://users.rcn.com/crfriend/museum           | ICBM: 42:22N 71:47W |

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