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Frank_G 03-06-2004 07:52 PM

dead computer - power supply voltage ?
 
I am trying to diagnose a machine and need a little help with the info on
page 1171 & 1141 of 'Upgrading & Repairing PCs - Scott Mueller' if anyone
has it.

Or perhaps it's help with how to read the voltage on my little radio shack
digital autoranging multimeter.

I have been presented with a dead computer. No boot, no beeps, no post -
just a little 'sound' action at the very beginning and then nothing.

All connector's appear to be seated in their sockets.

I tried replacing with a known-good stick of ram.

I tried replacing the video card. There are no other pci cards.

The power supply is an Astec 145W in an older IBM PC300GL. The fan's running
& the led lights are on & I've used the 'back probe' technique (see book
above) to check the
voltage from the power supply is sufficient to boot and it reads DC voltage
5.0V which should be
right on ?

However, after weeks of frustration I managed to get hold of an identical
machine, that is working great - no problems, and had an opportunity to do
the back-probe test on it for comparison - but here the autoranging DC
voltage readout is 32.0 mV (millivolts) !

Now why would it be so much less - It just doesn't make sense. This working
machine has nic& video cards, floppy & cd drives,

Can you explain the situation? And what to do ?
How can I tell if it's the mobo or cpu without a post card, and without
yanking the cpu from the known good machine?

Thank you in anticipation,
Frank



--
xx



DH 03-06-2004 08:32 PM

Re: dead computer - power supply voltage ?
 
Have you taken the m'board out to check for stray screws "lodged"
beneath(between) the case and m'board?

"Frank_G" <someone@hotmail.com> wrote in message
news:LWp2c.6113$i_2.125997@news20.bellglobal.com.. .
> I am trying to diagnose a machine and need a little help with the info on
> page 1171 & 1141 of 'Upgrading & Repairing PCs - Scott Mueller' if anyone
> has it.
>
> Or perhaps it's help with how to read the voltage on my little radio shack
> digital autoranging multimeter.
>
> I have been presented with a dead computer. No boot, no beeps, no post -
> just a little 'sound' action at the very beginning and then nothing.
>
> All connector's appear to be seated in their sockets.
>
> I tried replacing with a known-good stick of ram.
>
> I tried replacing the video card. There are no other pci cards.
>
> The power supply is an Astec 145W in an older IBM PC300GL. The fan's

running
> & the led lights are on & I've used the 'back probe' technique (see book
> above) to check the
> voltage from the power supply is sufficient to boot and it reads DC

voltage
> 5.0V which should be
> right on ?
>
> However, after weeks of frustration I managed to get hold of an identical
> machine, that is working great - no problems, and had an opportunity to do
> the back-probe test on it for comparison - but here the autoranging DC
> voltage readout is 32.0 mV (millivolts) !
>
> Now why would it be so much less - It just doesn't make sense. This

working
> machine has nic& video cards, floppy & cd drives,
>
> Can you explain the situation? And what to do ?
> How can I tell if it's the mobo or cpu without a post card, and without
> yanking the cpu from the known good machine?
>
> Thank you in anticipation,
> Frank
>
>
>
> --
> xx
>
>




bardeban 03-06-2004 08:56 PM

Re: dead computer - power supply voltage ?
 
There are no more juice in the capacitors of your mobo, or the CPU is gone
north.

"Frank_G" <someone@hotmail.com> wrote in message
news:LWp2c.6113$i_2.125997@news20.bellglobal.com.. .
> I am trying to diagnose a machine and need a little help with the info on
> page 1171 & 1141 of 'Upgrading & Repairing PCs - Scott Mueller' if anyone
> has it.
>
> Or perhaps it's help with how to read the voltage on my little radio shack
> digital autoranging multimeter.
>
> I have been presented with a dead computer. No boot, no beeps, no post -
> just a little 'sound' action at the very beginning and then nothing.
>
> All connector's appear to be seated in their sockets.
>
> I tried replacing with a known-good stick of ram.
>
> I tried replacing the video card. There are no other pci cards.
>
> The power supply is an Astec 145W in an older IBM PC300GL. The fan's

running
> & the led lights are on & I've used the 'back probe' technique (see book
> above) to check the
> voltage from the power supply is sufficient to boot and it reads DC

voltage
> 5.0V which should be
> right on ?
>
> However, after weeks of frustration I managed to get hold of an identical
> machine, that is working great - no problems, and had an opportunity to do
> the back-probe test on it for comparison - but here the autoranging DC
> voltage readout is 32.0 mV (millivolts) !
>
> Now why would it be so much less - It just doesn't make sense. This

working
> machine has nic& video cards, floppy & cd drives,
>
> Can you explain the situation? And what to do ?
> How can I tell if it's the mobo or cpu without a post card, and without
> yanking the cpu from the known good machine?
>
> Thank you in anticipation,
> Frank
>
>
>
> --
> xx
>
>




GRAHAM BARNES 03-06-2004 09:31 PM

Re: dead computer - power supply voltage ?
 
I repair as hobby. MB would be suspect 20 to 1 over cpu failure! (maybe
greater). Suggest you try and snuggle up good
working machine next to dead (dark) one and plug in main power plug
connector. This will eliminate weak or failing power supply
in bad machine. Also when trouble shooting at the drastic level, its a good
idea to have everything else off and out. That means no
cards other than the video, no hdd, no floppy , no anything! Two more checks
before the trash can! Change video card at this
point. Still dark? Now you have eliminated every possibility except the
board itself! BUT you didn't mention the RTC! That's the
CMOS! Same thing. Real Time Clock= Complimentary Metal Oxide
Semiconductor. Its the time keeping chip and it will go
BLANK!!!! and cause what you have! There is a jumper on the board with pins
1-2-3. Cap is on 1-2 or 2-3. Move cap
to other pins for 5 SECONDS! That's all! If the computer starts date,
time all will be off....must be reset. Other wise...its cooked!!
Rich S. Bryn Mawr, Pa. P.S. You can try cpu exchange as last resort. I
just put them in drawer and assume they are good!
Never had one fail since 1990! Only reason to suspect if machine has been
subjected to power surge, say during an outage cycle.
"Frank_G" <someone@hotmail.com> wrote in message
news:LWp2c.6113$i_2.125997@news20.bellglobal.com.. .
> I am trying to diagnose a machine and need a little help with the info on
> page 1171 & 1141 of 'Upgrading & Repairing PCs - Scott Mueller' if anyone
> has it.
>
> Or perhaps it's help with how to read the voltage on my little radio shack
> digital autoranging multimeter.
>
> I have been presented with a dead computer. No boot, no beeps, no post -
> just a little 'sound' action at the very beginning and then nothing.
>
> All connector's appear to be seated in their sockets.
>
> I tried replacing with a known-good stick of ram.
>
> I tried replacing the video card. There are no other pci cards.
>
> The power supply is an Astec 145W in an older IBM PC300GL. The fan's

running
> & the led lights are on & I've used the 'back probe' technique (see book
> above) to check the
> voltage from the power supply is sufficient to boot and it reads DC

voltage
> 5.0V which should be
> right on ?
>
> However, after weeks of frustration I managed to get hold of an identical
> machine, that is working great - no problems, and had an opportunity to do
> the back-probe test on it for comparison - but here the autoranging DC
> voltage readout is 32.0 mV (millivolts) !
>
> Now why would it be so much less - It just doesn't make sense. This

working
> machine has nic& video cards, floppy & cd drives,
>
> Can you explain the situation? And what to do ?
> How can I tell if it's the mobo or cpu without a post card, and without
> yanking the cpu from the known good machine?
>
> Thank you in anticipation,
> Frank
>
>
>
> --
> xx
>
>




Blinky the Shark 03-07-2004 01:03 AM

Re: dead computer - power supply voltage ?
 
Frank_G wrote:

> I am trying to diagnose a machine and need a little help with the info on
> page 1171 & 1141 of 'Upgrading & Repairing PCs - Scott Mueller' if anyone
> has it.


I have no help on this issue, but just wanted to say you have excellent
taste in books. I've had two editions of that one, and it's awesome.
And being 56, I don't toss the word "awesome" about casually. :)

--
Blinky Linux RU 4892F
http://linuxnotjustforgeeks.org
http://blinkynet.net
http://blinkynet.net/spag/w2000src.html - Win Source Code Leak

Frank_G 03-07-2004 03:53 AM

Re: dead computer - power supply voltage ?
 



>
> > I am trying to diagnose a machine and need a little help with the info

on
> > page 1171 & 1141 of 'Upgrading & Repairing PCs - Scott Mueller' if

anyone
> > has it.

>
> I have no help on this issue, but just wanted to say you have excellent
> taste in books. I've had two editions of that one, and it's awesome.
> And being 56, I don't toss the word "awesome" about casually. :)

===============================================
Thanks,we're a similar vintage so we appreciate the same things :-)

I think my problem is with the mobo.

For your interest, here is the story:
Fortunately, I had the identical unit available tonight on loan, in good
working
order, to swap parts.
I used 1 x stick of known good ram.
I replaced the psu with the known good one.
I replaced the cpu (difficult darned clips to manage - the old zif lever was
so much easier - but I digress:-) with a known good one.
Still no action - no beeps, no post, nothing. Just a bit of sound of some
action at the very beginning.
I didn't worry much about the video card, or the ribbon cable to the hard
drive as I figured if they were the cause, I'd at least get some beeps -
correct? Or .......mmmmm......if there's a problem with the HD (e.g. a
short) could this have created the symptom?
By deduction, would you agree that it's the mobo ?
If so, I guess the machine is toast, maybe salvage a few parts for the
future.



Frank_G 03-07-2004 04:32 AM

Re: dead computer - power supply voltage ?
 


no, it's not the HD - just tested it



> > > I am trying to diagnose a machine and need a little help with the info

> on
> > > page 1171 & 1141 of 'Upgrading & Repairing PCs - Scott Mueller' if

> anyone
> > > has it.

> >
> > I have no help on this issue, but just wanted to say you have excellent
> > taste in books. I've had two editions of that one, and it's awesome.
> > And being 56, I don't toss the word "awesome" about casually. :)

> ===============================================
> Thanks,we're a similar vintage so we appreciate the same things :-)
>
> I think my problem is with the mobo.
>
> For your interest, here is the story:
> Fortunately, I had the identical unit available tonight on loan, in good
> working
> order, to swap parts.
> I used 1 x stick of known good ram.
> I replaced the psu with the known good one.
> I replaced the cpu (difficult darned clips to manage - the old zif lever

was
> so much easier - but I digress:-) with a known good one.
> Still no action - no beeps, no post, nothing. Just a bit of sound of some
> action at the very beginning.
> I didn't worry much about the video card, or the ribbon cable to the hard
> drive as I figured if they were the cause, I'd at least get some beeps -
> correct? Or .......mmmmm......if there's a problem with the HD (e.g. a
> short) could this have created the symptom?
> By deduction, would you agree that it's the mobo ?
> If so, I guess the machine is toast, maybe salvage a few parts for the
> future.
>
>




Blinky the Shark 03-07-2004 05:58 AM

Re: dead computer - power supply voltage ?
 
Frank_G wrote:

> For your interest, here is the story:
> Fortunately, I had the identical unit available tonight on loan, in good
> working
> order, to swap parts.
> I used 1 x stick of known good ram.
> I replaced the psu with the known good one.
> I replaced the cpu (difficult darned clips to manage - the old zif lever was
> so much easier - but I digress:-) with a known good one.


Hope you took the time to properly deal with the heat transfer material between
the CPUs and the heat sinks.

> Still no action - no beeps, no post, nothing. Just a bit of sound of some
> action at the very beginning.


What kind of sound -- drive heads?

> I didn't worry much about the video card, or the ribbon cable to the hard
> drive as I figured if they were the cause, I'd at least get some beeps -
> correct? Or .......mmmmm......if there's a problem with the HD (e.g. a
> short) could this have created the symptom?
> By deduction, would you agree that it's the mobo ?


It's sounding like that, yeah. If it were a video problem, frex, you'd
probably be getting "bad video" beeps from BIOS.

> If so, I guess the machine is toast, maybe salvage a few parts for the
> future.


Why? Why not just replace the mobo? (Unless this is a good time for
you to do that overall upgrade you've been itching for. <g>)

--
Blinky Linux RU 4892F
http://linuxnotjustforgeeks.org
http://blinkynet.net
http://blinkynet.net/spag/w2000src.html - Win Source Code Leak

Frank_G 03-07-2004 02:17 PM

Re: dead computer - power supply voltage ?
 

>
> Hope you took the time to properly deal with the heat transfer material

between
> the CPUs and the heat sinks.


no, they come out together in one piece.

> Why? Why not just replace the mobo? (Unless this is a good time for
> you to do that overall upgrade you've been itching for. <g>)
>


it's an older cpu/mb - not sure where i'd ever find a replacement board




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