10 Jun
2002
10 Jun
'02
10:59 p.m.
I have these two external drive cases, once called "Leprechaun boxes";
one held an external RD52 and one held an external TK50 - same enclosure,
same PSU, different cable transition header at the back.
The problem is that every one of these that I've ever seen has had the
PSU die. One of these was repaired by my order (with company funds!)
about 15 years ago by ESS. I don't fancy a professional replacement
at this stage.
I do not have schematics. I do not not understand switching PSUs
well enough to do more than take stabs. I know they involve high
voltage, high-frequency oscillations, but that doesn't help me fix
them. :-( Is anyone on the list familiar with these enough to
suggest common failure modes?
If the case were a wee bit taller and wider, I'd consider putting
a commodity PSU in the cage. Don't think there's room for one in
there, though. Not desktop sized, anyway. Anyone have ratings for
the Leprechaun box? Looks like .45A @ 125V from the back, which tells
me that it's not a strong PSU (~60W max draw, so probably no more than
40-50W pull, I'd guess). I wish I'd bought more of these $5 tiny
cases at Dayton a couple of years ago - the PSUs will fit into your
palm and provide at least that much current (enough to drive a small
PeeCee motherboard and a 3.5" drive).
Thanks for any assistance.
-ethan
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11 Jun
11 Jun
1:55 p.m.
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2:23 p.m.
--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote:
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.
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.
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... 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. 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
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7:04 p.m.
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12 Jun
12 Jun
9:31 a.m.
--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote:
Oh, what the heck, I've dug mine out and pulled
the PSU. Alas I don't
think it's quite the same unit. The PSU connectors sound similar, but the
mains smoothing caps in mine are 330uF 250V. There are also 2 fuses on
the PSU board itself -- F1 is a 1.25" (3AG?) fuse in series with the
mains input and F2 is a soldered-in fuse...
Nope. Not the same at all. I have three identical units, but no fuses.
Anyway, on my PCB there's a 120k resistor (looks
to be about 0.5W,
small)running parallel to the long edge of the PCB between the 2 mains
smoothing capacitors. At a quick glance that's the startup resistor.
I'll check for something that looks like that.
My PSU is made by 'Joule Power', apparently.
Mine, too, but I don't have the model number with me at work.
I looked into the third PSU - it has a fried diode near the output
connectors - cracked and blackened. There is also a small area of
discoloration under some 1/8 and 1/4 W resistors located toward
the input side of the board, between the large transformer/inductor
and the input taps.
The other two are clean.
I'll look into that 0.5W resistor. An easy fix if that's what it
is.
Thanks again,
-ethan
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5:56 p.m.
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13 Jun
13 Jun
12:54 a.m.
--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote:
None. I know what pico fuses look like. There is nothing anywhere
on these boards that resembles a fuse. I would expect one, too.
There isn't one.
On the back side, in copper, mine says...
JOULE POWER inc
107-001-027
and elsewhere it says, in copper
LCT60
and in ink
LCT60-1202
and on the top, in ink
802256101 rev c1
Good news is I found *another one*. This one (TK50) might have a working
supply. Have to check it out later.
-ethan
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--- Tony Duell <ard(a)p850ug1.demon.co.uk> wrote:
fuses.
I am suprised. Are you sure there's not a soldered-in fuse (which might
look more like a resistor)? Oh, what the heck, I've dug mine out and
pulled the PSU...
Nope. Not the same at all. I have three identical units, but no > > Anyway, on my PCB there's a 120k
resistor (looks to be about 0.5W,
> > running parallel to the long edge of the PCB...
I can't find anything that closely resembles that. There is a largish
3K ceramic resistor next to the 470uF caps... it's good in all three
PSUs.
> My PSU is
made by 'Joule Power', apparently.
I've put my box away again. I
couldn't see an obvious model number on the
PSU board last night, but if you do post the numbers on yours I can dig
my unit out again and see if I can match them at all.
8243
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