Computer won't turn on!

[Paul]

I'd rather it be the power supply than the mobo! (Although it's not
the origina PSU and is only 3 or 4 years old. It was low-priced so
might be failing already.

Thanks and thanks, GT.

1) Check the motherboard capacitors for bulging or swelling (the 5+6=11 or so
near the CPU socket).

2) Unplug and visually examine the 20 pin main connector, for burned pins
or discoloration. Your motherboard likely uses a bit of +5V. If the
main connector wasn't fully seated, and the latch on the connector
engaged, sometimes the connector gets burned.

Paul

 

[Nobody > (Revisited)]

So definitely not the switch. I still live in the 50's, where if
something goes on only sometimes, it's the switch. Why can't life be
like that anymore. Bwaaaahhh.

Tell me about that.. I'm self-taught on them pesky electrons, was
repairing TVs in 1959 at age 9. I'll admit that tubes/valves were easy,
especially if you had both a full tube caddy and a decent tubetester. I
got lucky and an old neighbor ham left me both in his will.

Switches?

Don't even get me started on the new-gen of test equipment. I hate to
have to wade thru 3 to 10 layers of button-push madness menus to change
ranges/timebases/etc on the newer o-scopes, when I could just reach up
and click-count on real knobs without looking with the old gear.

(But then again, (except for bad tubes back then) about 80% of all fails
and intermittents were mechanical switches or contacts)
--
"Shit this is it, all the pieces do fit.
We're like that crazy old man jumping
out of the alleyway with a baseball bat,
saying, "Remember me motherfucker?"
Jim “Dandy” Mangrum

 

[larry moe 'n curly]

By any chance, do you still have a 3.5" floppy drive in this box?

If the data cable is plugged in "upside down" at the drive, that often
stops the machine from starting (as in not showing a boot/BIOS screen).
Some BIOs/chipset variants would sometimes allow an occasional "start"
with this. (probably some kind of fail-fall-back?).

The prime on this is that the floppy's "activity light" would stay lit
all the time.

(as an aside, this goof usually nuked any media in the drive)

I've experienced data nuking by plugging in the floppy cable
backwards , but I thought the floppy disk interface was "open
collector" or "open drain", meaning it withstood shorts to ground just
fine because it normally enabled signals by shorting them to ground
anyway.

 

[mm]

Tell me about that.. I'm self-taught on them pesky electrons, was
repairing TVs in 1959 at age 9. I'll admit that tubes/valves were easy,
especially if you had both a full tube caddy and a decent tubetester. I
got lucky and an old neighbor ham left me both in his will.

Very good. I didn't know anyone like that, well, ever.

But I did get a tube tester for cheap at Lafayette Radio when I was
about 28. They said they woudl get me the manual. It took my nagging
them and about 6 months but they did get me an original manual. It's
downstairs but I forget the brand.

Switches?

Don't even get me started on the new-gen of test equipment. I hate to
have to wade thru 3 to 10 layers of button-push madness menus to change
ranges/timebases/etc on the newer o-scopes, when I could just reach up
and click-count on real knobs without looking with the old gear.

I didn't even know about this. I have an Eico-kit scope that I
bought assembled. It was sitting on a high shelf in an electronics
parts store near City Hall in NYC, 30 years ago. But eitehr I don't
know how to use it, or it's not so good, because I've never gotten the
images the Sam's manuals say should be present at certain spots in tv
circuits.

So I wanted to buy a used scope. Sometimes they are at hamfests,
cheap, but one day a guy had 20 dual-trace scopes, all looked like
new. I wasn't in the right mood to buy one, and I figured there would
be more opportunities. I hope it's not the ones with menus that I see
in the future.

(But then again, (except for bad tubes back then) about 80% of all fails
and intermittents were mechanical switches or contacts)

Beyond tubes and physical damage, I was never that good at fixing
this stuff, but it's gotten harder of course.

 

[mm]

Yes, I have a 3.5 and I also have a 5.25! And I used the 5.25 this
past year, trying to retrieve data from a friend's floppy from her
first job. (She couldn't rememmber what kind of computer or word
processor she had been using. I finally found something to read the
format, it said, and it said there was a little but barely anything on
the floppy._)

But I was careful to plug in the cable right and they've both been
working for 5 years plus. So how could they be wrong?

(I'll put them on my checklist, however. My new-used Dell didn't have
a floppy, and the CD drives weren't working, so I dangled a spare one
so that I could add the 3 files I found missing. (Ntdetect.com,
boot.ini, and autoexec???.nt. I don't know why they were missing and
no others afaict.)

No the light's not on and I've only had trouble with second-hand
floppies.

 

[mm]

1) Check the motherboard capacitors for bulging or swelling (the 5+6=11 or so
near the CPU socket).

2) Unplug and visually examine the 20 pin main connector, for burned pins
or discoloration. Your motherboard likely uses a bit of +5V. If the
main connector wasn't fully seated, and the latch on the connector
engaged, sometimes the connector gets burned.

Paul

OKay, thanks.

 

[mm]

That's important because when that LED stays dim, the problem is
almost always the PSU or a short. But if the LED does light up, it
can still be the PSU, and the need for multiple turn-on attempts point
to worn out electrolytic capacitors in the PSU.


Usually only an AGP card or 1x PCI-E card (narrow connector) will be
unseated, unless the computer has recently been moved, worked on, or a
cable in back has been installed or tugged.
Another thing to consider is a short between the motherboard and case,
usually around one of the mounting holes (screw needs electrically
insulating washer on top or bottom of hole) or at a corner (not
supported, can flex enough to short -- install rubber stick-on bumper
foot at corner, to case).

It might well have been related!

Take a flashlight and magnifying glass and look at each contact of the
DIMM sockets because sometimes there's a piece of junk in them (broken
piece of plastic, tiny surface mount part that tore off, or even a
piece of solder), or a contact can get mangled (you may be able to
straighten it with a dental pick or jeweler's screwdriver).

You were right on the money. I took the DIMM all the way out and
looked in the slot and there was something. Then I noticed the yellow
wire to the CPU fan was cut, and the thing in the slot was a piece of
yellow insulation. (Yet I was still able to get latches at both ends
to close, and even snap closed the last time. But the 500K never
showed up.)

I took out the insulation, put the DIMM in, and now the 500K is seen.

The failure to turn on problem might have started when I first put the
DIMM in.

It's embarrassing to tell you I caught a wire in doing so, but I have
to lean over the desk and push the wires aside while I'm holding
myself up with one arm and moving the wires with the other, and
holding the flashlight with my other arm.

Since it only gave me trouble every month or two, I guess it will take
several months to have a good impression that the start-up problem is
fixed, but we may have killed two birds with one stone.

Thanks.

 

[mm]

Your motherboard likely uses a bit of +5V.

Google search for "ATX Connector" and you'll find that the 5 it uses
for standby is marked 5vSB. If you have the LED at full brightness you
have what you need.

I've made the decision to replace CR2032s if they won't crank 3.0. And
in an emergency I've used 2025s or 2016s. And I measure with a digital
meter as analog kills the coin batteries.

WRT tube TVs, there was the old standby, contact cleaner. Probably
could dig some tubes out of the parts bin and still have the remains of
at least one can of contact cleaner. Got to use it on telephone relays
in IBM punch card equipment.

Saved my old Heathkit 20mhz scopes for repair one of these days when I
get round tuit. Went to a professional scope until it died and haven't
had need since. Also had one of the hernia Teks for a while, 465 I
think it was. 80 or so pounds, and more knobs than I have fingers and
toes.

Is it their fault you don't have enough toes?