--- Tony Duell <ard_at_p850ug1.demon.co.uk> wrote:
> >
> >
> > I have these two external drive cases, once called "Leprechaun boxes";
>
> I think I have one too. A metal box with plastic front and back panels.
> It contains (in my case) an RD53, the PSU and a little PCB carrying the
> on-line and write-protect swtiches...
Precisely. The little PCB for the box I was playing with last night
happens to be plumbed for two write-protect lights and no switches
(external RX50 case for an RUX50 controller - boy was that expensive
new, but we had to make distro floppies from our 11/750). Different
innards had different front and back boards.
> Alas mine was modified by the
> previous owner so those don't connect to anything -- I fitted a DD50
> socket on the back (the cutout was clearly designed to take one)
> connected to the drive's edge connectors.
Done that, too. I removed the board with 3 x DD50 and replaced it with
a DD50 cable from an old Sun3 monster external drive box and a homemade
panel for SCSI select switches. I was using it for DAT and CD-ROM on
my SPARC1 until the PSU died. Lately, it's been a mouse-pad stand
for my SPARC5. :-P I intend to return it to "normal" service once
I get a working PSU.
> Could this be the same unit? If so, I will try to find it and look at the
> PSU for you.
Almost certainly. It has a 3-pin Molex connector with D-shaped pins
for keys as the mains input, a 6-pin .1" connector with two wires
going to the 115V/230V selector, and a multi-pin heavy-duty connector
like in a BA23 with a harness to the contents. If your PSU looks much
different, then there are only external similarities.
> > The problem is that every one of these that I've ever seen has had the
> > PSU die
>
> I assume there are no outputs at all, and that the PSU does not make the
> 'tweet tweet' noise of an SMPUS that's attempting to start, finding
> problems, and shutting down repeatedly.
No output on +5 or +12. There _might_ be a single tweet, but not
a series of tweets indicating a dead-nasty-short condition. I did
get a tingle (when the mains were disconnected and the board was on
the table!) between two of the heat sinks, so I know _something_ is
alive in there.
> First check, the interal mains fuse. You'rs not just looking to see if it
> has blown...
Good advice, but not in this situation. There is no fuse in my box.
There is a circuit breaker in the back of the enclosure that interrupts
power to the inside of the PSU cage. I have mains voltage at the
inputs to the PSU board. The power switch does turn it on and off.
> 3) It's OK. Most likely the startup resistor is open-circuit. Look for a
> resisotr of a few hunderd kilohms connected between the +ve side of the
> mains smoothing capacitor and a point deep in the circuitry. Make sure
> it's not open. This is a very common problem with SMPSUs, BTW.
OK. Large (1W)? small (1/8W)? There are two largish capacitors,
470uF and marked 200 WV, whatever a WV is (Watt-Volt?) I have
multiple PSUs. In the one, the top of one of these caps seemed
inflated, so I thought it might be blown. I removed it, but the
bottom shows no physical distortion. The plastic top seems to
have some light pressure behind it. I pulled a cap of the same
value from another PSU in a different location, inspected it
and installed it. No change. I have a hand-held capacitance
meter, but it peaks at 200uF and it seems to not like polarized
caps. The cap inputs are not marked +/- in any way.
> Anyway, let me know the state of the fuse and if necessary I'll dig out
> my unit (if it's the same) and look at the PSU.
Even though it is a voltage-selectable PSU, perhaps we may not have
the same unit. I'll see about getting some pictures up on a web page.
Not sure if I can manage that tonight. I need this box at work with
me tomorrow, so I was going to embed a wall wart in the PSU cage
to get me through a presentation tomorrow night (running a Vacuum
Flourescent Display at a Linux SIG meeting/Mozilla Party).
I do want to learn more about the PSU so I can fix all three. I just
don't know how much I can do this week.
Thanks!
-ethan
__________________________________________________
Do You Yahoo!?
Yahoo! - Official partner of 2002 FIFA World Cup
http://fifaworldcup.yahoo.com
Received on Tue Jun 11 2002 - 14:23:18 BST