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"Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."



 
 
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  #21  
Old December 23rd 19, 12:24 AM posted to alt.comp.hardware
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."

Norm Why wrote:
The safety ground on the three prong plug, should be joined to the
chassis ground.

You are allowed to test the system with no SATA cables in place.

You can bring up a machine and enter the BIOS, while no hard drives
or optical drives are connected. This would allow you to observe
system operation as SATA cables are added to a successfully running
(so far) system.

Paul
Thanks Paul,

I've even removed the beep speaker to find the short. Ohm meter says
short is low resistance. Step one in two-page diagnostic troubleshooting
flow chart must be wrong , or it is a bad, bad short.

Assuming Step One was wrong. I carried on down to Plug in Power supply.
Turn power on. No Beep, momentary power, system drops dead. Short must be
real and getting worse, or system is learning how to be more
uncooperative.


The short to ground goes through the 4pin 12V connector.



Did you reverse it ?

The 2x2 has shaped enclosures for the pins,
and they are only intended to fit one way.
The two pieces that form a latch, should be
on the same side.

If a power supply has become weak with age, it
can shut down when less than the rated load
is present.

You'd need a clamp-on ammeter, to easily be able
to make measurements of current flows on the various
rails. For example, if the main PSU connector
has four +5V wires, you put all four within the
jaws of a DC clamp-on ammeter, and the meter
gives the total current flow in the four wires.

For the first 35 milliseconds, the supply ignores
overloads. This gives time for the main outputs to
charge any capacitors present. It's after that
point, that it starts looking for overloads.

I do my initial builds, on the kitchen table,
using a phone book as an "insulating base". Once the
components are proved working, then I start installing
the stuff in a computer case. and this gives an opportunity
to compare symptoms between "insulated" and "grounded".

Paul
  #22  
Old December 23rd 19, 01:13 AM posted to alt.comp.hardware
Norm Why[_2_]
external usenet poster
 
Posts: 114
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."

You are allowed to test the system with no SATA cables in place.

You can bring up a machine and enter the BIOS, while no hard drives
or optical drives are connected. This would allow you to observe
system operation as SATA cables are added to a successfully running
(so far) system.

Paul
Thanks Paul,

I've even removed the beep speaker to find the short. Ohm meter says
short is low resistance. Step one in two-page diagnostic
troubleshooting flow chart must be wrong , or it is a bad, bad short.

Assuming Step One was wrong. I carried on down to Plug in Power supply.
Turn power on. No Beep, momentary power, system drops dead. Short must
be real and getting worse, or system is learning how to be more
uncooperative.


The short to ground goes through the 4pin 12V connector.


Did you reverse it ?


No. Even removed I still have short to ground.

The 2x2 has shaped enclosures for the pins,
and they are only intended to fit one way.
The two pieces that form a latch, should be
on the same side.

If a power supply has become weak with age, it
can shut down when less than the rated load
is present.

You'd need a clamp-on ammeter, to easily be able
to make measurements of current flows on the various
rails. For example, if the main PSU connector
has four +5V wires, you put all four within the
jaws of a DC clamp-on ammeter, and the meter
gives the total current flow in the four wires.

For the first 35 milliseconds, the supply ignores
overloads. This gives time for the main outputs to
charge any capacitors present. It's after that
point, that it starts looking for overloads.

I do my initial builds, on the kitchen table,
using a phone book as an "insulating base". Once the
components are proved working, then I start installing
the stuff in a computer case. and this gives an opportunity
to compare symptoms between "insulated" and "grounded".

Paul


I am now pondering my silly collection of MOBO mounting screws.

https://www.aliexpress.com/item/32957035974.html

Shows nylon screws that can be used for mounting or standoffs. Standoffs
don't work for me because I need PCI VGA card.

Size:
M2 (Thread 6mm)
M2.5 (Thread 6mm)
M3 (Thread 6mm)
M4 (Thread 6mm)

I guess 'size' is pitch, because all are 6mm thread.

What size would work?

Length:
5mm (50pcs)
6mm (50pcs)
7mm (50pcs)
8mm (50pcs)
9mm (50pcs)
10mm (50pcs)
11mm (50pcs)
12mm (50pcs)
13mm (50pcs)
14mm (50pcs)
15mm (50pcs)
16mm (50pcs)
17mm (50pcs)
18mm (50pcs)
19mm (50pcs)
20mm (50pcs)
21mm (50pcs)
22mm (50pcs)
23mm (50pcs)
24mm (50pcs)
25mm (50pcs)
26mm (50pcs)
28mm (50pcs)
30mm (50pcs)
32mm (50pcs)
35mm (50pcs)
40mm (50pcs)
45mm (50pcs)
50mm (50pcs)

What Length would work?



  #23  
Old December 23rd 19, 06:00 AM posted to alt.comp.hardware
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini OnboardCase Buzzer Board Beep Alarm NEW."

Norm Why wrote:
You are allowed to test the system with no SATA cables in place.

You can bring up a machine and enter the BIOS, while no hard drives
or optical drives are connected. This would allow you to observe
system operation as SATA cables are added to a successfully running
(so far) system.

Paul
Thanks Paul,

I've even removed the beep speaker to find the short. Ohm meter says
short is low resistance. Step one in two-page diagnostic
troubleshooting flow chart must be wrong , or it is a bad, bad short.

Assuming Step One was wrong. I carried on down to Plug in Power supply.
Turn power on. No Beep, momentary power, system drops dead. Short must
be real and getting worse, or system is learning how to be more
uncooperative.
The short to ground goes through the 4pin 12V connector.

Did you reverse it ?


No. Even removed I still have short to ground.

The 2x2 has shaped enclosures for the pins,
and they are only intended to fit one way.
The two pieces that form a latch, should be
on the same side.

If a power supply has become weak with age, it
can shut down when less than the rated load
is present.

You'd need a clamp-on ammeter, to easily be able
to make measurements of current flows on the various
rails. For example, if the main PSU connector
has four +5V wires, you put all four within the
jaws of a DC clamp-on ammeter, and the meter
gives the total current flow in the four wires.

For the first 35 milliseconds, the supply ignores
overloads. This gives time for the main outputs to
charge any capacitors present. It's after that
point, that it starts looking for overloads.

I do my initial builds, on the kitchen table,
using a phone book as an "insulating base". Once the
components are proved working, then I start installing
the stuff in a computer case. and this gives an opportunity
to compare symptoms between "insulated" and "grounded".

Paul


I am now pondering my silly collection of MOBO mounting screws.

https://www.aliexpress.com/item/32957035974.html

Shows nylon screws that can be used for mounting or standoffs. Standoffs
don't work for me because I need PCI VGA card.

Size:
M2 (Thread 6mm)
M2.5 (Thread 6mm)
M3 (Thread 6mm)
M4 (Thread 6mm)

I guess 'size' is pitch, because all are 6mm thread.

What size would work?

Length:
5mm (50pcs)
6mm (50pcs)
7mm (50pcs)
8mm (50pcs)
9mm (50pcs)
10mm (50pcs)
11mm (50pcs)
12mm (50pcs)
13mm (50pcs)
14mm (50pcs)
15mm (50pcs)
16mm (50pcs)
17mm (50pcs)
18mm (50pcs)
19mm (50pcs)
20mm (50pcs)
21mm (50pcs)
22mm (50pcs)
23mm (50pcs)
24mm (50pcs)
25mm (50pcs)
26mm (50pcs)
28mm (50pcs)
30mm (50pcs)
32mm (50pcs)
35mm (50pcs)
40mm (50pcs)
45mm (50pcs)
50mm (50pcs)

What Length would work?


The trick is not to lose the hardware that came with the
computer case.

The standoffs are custom length, intended to elevate the
PCB to be flush with the slot holes for the I/O cards, in
the back. There's no way for me to guess any such measurement
from here. There are as many styles of solutions, as there
are days of the week.

If you artificially elevate the motherboard, with too-tall
standoffs, then your video card won't fit.

It's one of the items on the buyers list, to check the
fit and dress of standoffs before buying a computer case.
And that's pretty hard to do. You can't always inspect
this issue in advance.

I used to look at computer cases at a mom&pop (single store),
while they were in business. Basically, any store in town that
put computer cases on display in a useful way, went out of
business. And I did buy cases from them, so it's not like
the effort on their part wasn't rewarded.

For example, I don't buy "bump" style trays. That's where
the metal of the tray is formed into a bump of the appropriate
height, then a hole drilled, then the hole is threaded. While
it saves the manufacturer $0.0001 per hole, it doesn't do me
any good. Instead, I like the brass standoffs that have a
male thread on one end and a female on the other, then the
motherboard screw fits to fasten the board down. These have
a better controlled contact area where it touches the
ground ring on the motherboard.

In terms of "places that short", there was one Asus motherboard
where the plastic socket frame around the CPU socket, was
fitted *before* the soldering step. The plastic went through
a wave solder perhaps, and it swept up some solder
underneath the plastic (hard to inspect) and it
shorted out VCore. But that would only cause VCore
with a current limiter to trip off. And a little repair
work, you could find and remove the short.

But for direct rail shorts, sometimes there can
be a short inside the motherboard, but it's less likely
there is a short, say, right at the 24 pin connector.

Some Biostar motherboards, used to join the yellow 12V wires
on the 2x2 ATX12V, to the 12V wires on the main 24 pin connector.
This is not a good idea, and I have no idea why Biostar was
doing that. The 12VA and 12VB should be separate from one
another, in case some old PSU with actual separate transformers
for those two 12V was in usage. The 12V on the ATX12V 2x2, could
be a different 12V than the 12V on the main connector (fraction
of a volt difference).

Since you say you are observing a short with the ATX12V removed,
then this suggests something on the rails on the main 24 pin
is shorted. But I don't see a cosmetic root cause, because the
transfer of some of those rails around the motherboard, is on
a buried layer. The motherboards have 4,6, or 8 layers, with
6 layers used for RAMBUS boards, 4 layers for a lot of regular
DDR motherboards, and 8 layers reserved for sockets with
huge pincounts, where it's just too hard to route all the
signals using a limited number of layers. Somewhere in
that stack, can be some 2oz layers for routing power.

At work, we would use a bed-of-nails tester for evaluating
"ohms". After a board came off the line, sometimes tests
were done that way too (JTAG), which isn't all that common
in the computer industry. Those are known as structural tests.
A company like Asus, would use a camera and automation to check
for visible flaws (stuff in places it doesn't belong), can
use an Xray machine for BGA verification, but for electrical
test, there is only a 2 minute hand functional test
(lady plugs boards into mobo and runs some test code for
two minutes total time, then product goes in box). They
rely on statistical sampling for quality, rather than
every board being inspected with a magnifying glass. Every
board receives the 2 minute functional test, but other
steps are likely automated.

To visually inspect a square foot of PCB, takes about 2 hours
with a 10x magnifier, because I've done a few boards visually,
and you do find stuff. (That's where I found a certain brand
of resistors, with all the bodies cracked in half.) At one
time, Asus made 5 million motherboards per month, and there's
no time for that sort of inspection, and they can only
sample motherboards and inspect them for manufacturing
defects, then go back to the line and correct them. Not every
motherboard can be treated like a Rolls Royce.

Paul
  #24  
Old December 23rd 19, 05:07 PM posted to alt.comp.hardware
Norm Why[_2_]
external usenet poster
 
Posts: 114
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."

[snippage]
I am now pondering my silly collection of MOBO mounting screws.

https://www.aliexpress.com/item/32957035974.html

Shows nylon screws that can be used for mounting or standoffs. Standoffs
don't work for me because I need PCI VGA card.

Size:
M2 (Thread 6mm)
M2.5 (Thread 6mm)
M3 (Thread 6mm)
M4 (Thread 6mm)

I guess 'size' is pitch, because all are 6mm thread.

What size would work?

Length:
5mm (50pcs)
6mm (50pcs)
7mm (50pcs)
8mm (50pcs)
9mm (50pcs)
10mm (50pcs)
11mm (50pcs)
12mm (50pcs)
13mm (50pcs)
14mm (50pcs)
15mm (50pcs)
16mm (50pcs)
17mm (50pcs)
18mm (50pcs)
19mm (50pcs)
20mm (50pcs)
21mm (50pcs)
22mm (50pcs)
23mm (50pcs)
24mm (50pcs)
25mm (50pcs)
26mm (50pcs)
28mm (50pcs)
30mm (50pcs)
32mm (50pcs)
35mm (50pcs)
40mm (50pcs)
45mm (50pcs)
50mm (50pcs)

What Length would work?


The trick is not to lose the hardware that came with the
computer case.

The standoffs are custom length, intended to elevate the
PCB to be flush with the slot holes for the I/O cards, in
the back. There's no way for me to guess any such measurement
from here. There are as many styles of solutions, as there
are days of the week.

If you artificially elevate the motherboard, with too-tall
standoffs, then your video card won't fit.

It's one of the items on the buyers list, to check the
fit and dress of standoffs before buying a computer case.
And that's pretty hard to do. You can't always inspect
this issue in advance.

I used to look at computer cases at a mom&pop (single store),
while they were in business. Basically, any store in town that
put computer cases on display in a useful way, went out of
business. And I did buy cases from them, so it's not like
the effort on their part wasn't rewarded.

For example, I don't buy "bump" style trays. That's where
the metal of the tray is formed into a bump of the appropriate
height, then a hole drilled, then the hole is threaded. While
it saves the manufacturer $0.0001 per hole, it doesn't do me
any good. Instead, I like the brass standoffs that have a
male thread on one end and a female on the other, then the
motherboard screw fits to fasten the board down. These have
a better controlled contact area where it touches the
ground ring on the motherboard.

In terms of "places that short", there was one Asus motherboard
where the plastic socket frame around the CPU socket, was
fitted *before* the soldering step. The plastic went through
a wave solder perhaps, and it swept up some solder
underneath the plastic (hard to inspect) and it
shorted out VCore. But that would only cause VCore
with a current limiter to trip off. And a little repair
work, you could find and remove the short.

But for direct rail shorts, sometimes there can
be a short inside the motherboard, but it's less likely
there is a short, say, right at the 24 pin connector.

Some Biostar motherboards, used to join the yellow 12V wires
on the 2x2 ATX12V, to the 12V wires on the main 24 pin connector.
This is not a good idea, and I have no idea why Biostar was
doing that. The 12VA and 12VB should be separate from one
another, in case some old PSU with actual separate transformers
for those two 12V was in usage. The 12V on the ATX12V 2x2, could
be a different 12V than the 12V on the main connector (fraction
of a volt difference).

Since you say you are observing a short with the ATX12V removed,
then this suggests something on the rails on the main 24 pin
is shorted. But I don't see a cosmetic root cause, because the
transfer of some of those rails around the motherboard, is on
a buried layer. The motherboards have 4,6, or 8 layers, with
6 layers used for RAMBUS boards, 4 layers for a lot of regular
DDR motherboards, and 8 layers reserved for sockets with
huge pincounts, where it's just too hard to route all the
signals using a limited number of layers. Somewhere in
that stack, can be some 2oz layers for routing power.

At work, we would use a bed-of-nails tester for evaluating
"ohms". After a board came off the line, sometimes tests
were done that way too (JTAG), which isn't all that common
in the computer industry. Those are known as structural tests.
A company like Asus, would use a camera and automation to check
for visible flaws (stuff in places it doesn't belong), can
use an Xray machine for BGA verification, but for electrical
test, there is only a 2 minute hand functional test
(lady plugs boards into mobo and runs some test code for
two minutes total time, then product goes in box). They
rely on statistical sampling for quality, rather than
every board being inspected with a magnifying glass. Every
board receives the 2 minute functional test, but other
steps are likely automated.

To visually inspect a square foot of PCB, takes about 2 hours
with a 10x magnifier, because I've done a few boards visually,
and you do find stuff. (That's where I found a certain brand
of resistors, with all the bodies cracked in half.) At one
time, Asus made 5 million motherboards per month, and there's
no time for that sort of inspection, and they can only
sample motherboards and inspect them for manufacturing
defects, then go back to the line and correct them. Not every
motherboard can be treated like a Rolls Royce.


Thanks Paul

From Google:

Thread: What size/kind of screws do I use for mounting motherboard?

Screw size depends on the size of the threads in the mobo standoffs, usually
M3x0.5 (metric) or #6-32 (US standard). I personally would not go over 6mm
or .25in in length. Head configuration is entirely up to you. Most
well-stocked hardware stores should have just about any size and type you
want.


  #25  
Old December 23rd 19, 06:45 PM posted to alt.comp.hardware
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini OnboardCase Buzzer Board Beep Alarm NEW."

Norm Why wrote:
[snippage]
I am now pondering my silly collection of MOBO mounting screws.

https://www.aliexpress.com/item/32957035974.html

Shows nylon screws that can be used for mounting or standoffs. Standoffs
don't work for me because I need PCI VGA card.

Size:
M2 (Thread 6mm)
M2.5 (Thread 6mm)
M3 (Thread 6mm)
M4 (Thread 6mm)

I guess 'size' is pitch, because all are 6mm thread.

What size would work?

Length:
5mm (50pcs)
6mm (50pcs)
7mm (50pcs)
8mm (50pcs)
9mm (50pcs)
10mm (50pcs)
11mm (50pcs)
12mm (50pcs)
13mm (50pcs)
14mm (50pcs)
15mm (50pcs)
16mm (50pcs)
17mm (50pcs)
18mm (50pcs)
19mm (50pcs)
20mm (50pcs)
21mm (50pcs)
22mm (50pcs)
23mm (50pcs)
24mm (50pcs)
25mm (50pcs)
26mm (50pcs)
28mm (50pcs)
30mm (50pcs)
32mm (50pcs)
35mm (50pcs)
40mm (50pcs)
45mm (50pcs)
50mm (50pcs)

What Length would work?

The trick is not to lose the hardware that came with the
computer case.

The standoffs are custom length, intended to elevate the
PCB to be flush with the slot holes for the I/O cards, in
the back. There's no way for me to guess any such measurement
from here. There are as many styles of solutions, as there
are days of the week.

If you artificially elevate the motherboard, with too-tall
standoffs, then your video card won't fit.

It's one of the items on the buyers list, to check the
fit and dress of standoffs before buying a computer case.
And that's pretty hard to do. You can't always inspect
this issue in advance.

I used to look at computer cases at a mom&pop (single store),
while they were in business. Basically, any store in town that
put computer cases on display in a useful way, went out of
business. And I did buy cases from them, so it's not like
the effort on their part wasn't rewarded.

For example, I don't buy "bump" style trays. That's where
the metal of the tray is formed into a bump of the appropriate
height, then a hole drilled, then the hole is threaded. While
it saves the manufacturer $0.0001 per hole, it doesn't do me
any good. Instead, I like the brass standoffs that have a
male thread on one end and a female on the other, then the
motherboard screw fits to fasten the board down. These have
a better controlled contact area where it touches the
ground ring on the motherboard.

In terms of "places that short", there was one Asus motherboard
where the plastic socket frame around the CPU socket, was
fitted *before* the soldering step. The plastic went through
a wave solder perhaps, and it swept up some solder
underneath the plastic (hard to inspect) and it
shorted out VCore. But that would only cause VCore
with a current limiter to trip off. And a little repair
work, you could find and remove the short.

But for direct rail shorts, sometimes there can
be a short inside the motherboard, but it's less likely
there is a short, say, right at the 24 pin connector.

Some Biostar motherboards, used to join the yellow 12V wires
on the 2x2 ATX12V, to the 12V wires on the main 24 pin connector.
This is not a good idea, and I have no idea why Biostar was
doing that. The 12VA and 12VB should be separate from one
another, in case some old PSU with actual separate transformers
for those two 12V was in usage. The 12V on the ATX12V 2x2, could
be a different 12V than the 12V on the main connector (fraction
of a volt difference).

Since you say you are observing a short with the ATX12V removed,
then this suggests something on the rails on the main 24 pin
is shorted. But I don't see a cosmetic root cause, because the
transfer of some of those rails around the motherboard, is on
a buried layer. The motherboards have 4,6, or 8 layers, with
6 layers used for RAMBUS boards, 4 layers for a lot of regular
DDR motherboards, and 8 layers reserved for sockets with
huge pincounts, where it's just too hard to route all the
signals using a limited number of layers. Somewhere in
that stack, can be some 2oz layers for routing power.

At work, we would use a bed-of-nails tester for evaluating
"ohms". After a board came off the line, sometimes tests
were done that way too (JTAG), which isn't all that common
in the computer industry. Those are known as structural tests.
A company like Asus, would use a camera and automation to check
for visible flaws (stuff in places it doesn't belong), can
use an Xray machine for BGA verification, but for electrical
test, there is only a 2 minute hand functional test
(lady plugs boards into mobo and runs some test code for
two minutes total time, then product goes in box). They
rely on statistical sampling for quality, rather than
every board being inspected with a magnifying glass. Every
board receives the 2 minute functional test, but other
steps are likely automated.

To visually inspect a square foot of PCB, takes about 2 hours
with a 10x magnifier, because I've done a few boards visually,
and you do find stuff. (That's where I found a certain brand
of resistors, with all the bodies cracked in half.) At one
time, Asus made 5 million motherboards per month, and there's
no time for that sort of inspection, and they can only
sample motherboards and inspect them for manufacturing
defects, then go back to the line and correct them. Not every
motherboard can be treated like a Rolls Royce.


Thanks Paul

From Google:

Thread: What size/kind of screws do I use for mounting motherboard?

Screw size depends on the size of the threads in the mobo standoffs, usually
M3x0.5 (metric) or #6-32 (US standard). I personally would not go over 6mm
or .25in in length. Head configuration is entirely up to you. Most
well-stocked hardware stores should have just about any size and type you
want.



Yes, that's the screw. But the length of the standoff and
what joins it to the motherboard, is up to the individual
computer case. The standoffs can be discrete brass items,
male threaded on one and and female threaded on top. And they
go into a flat tray metalwork which has threaded holes in
at least 9 standard places. Usually the tray has holes
drilled and threaded for several PCB standards.

But some trays dispense with the brass standoffs. Instead
of the metal tray being perfectly flat, it's formed so that
there are nine "bumps" in the metal, raised a certain height
above the plane of the rest of the metal. The bump has a threaded
hole in the top. This means they don't have to place nine
finely crafted brass standoffs in the box-of-hardware. And
I find the bump concept a bit worse, as the bump might be
less precise where it touches the motherboard (larger
footprint, in danger of exceeding the keep-out area around
the PTH plated through hole).

The height of the motherboard above the tray is "custom"
to a computer case design. This is why the brass standoffs
cannot be swapped from an Antec to a Compucase. You can see
that in the collection this guy has on hand, to take this picture.

"Various types of motherboard standoffs"

https://en.wikipedia.org/wiki/Comput...MGP5029_wp.jpg

( https://en.wikipedia.org/wiki/Computer_case_screws )

To me, in that picture, I think I'm seeing some
different diameter holes on the female ends of
the depicted standoffs. Compare the center three
brass items, to see how much difference there
can be in the screw choices. The head of the
motherboard fastener screw has to be small enough,
to stay within the keepout zone maintained by the
motherboard designer (the PCB has a multitude of
keepouts, like a square-ish pattern around the
CPU socket for the items placed on top of the CPU).

That's why my advice is:

"Don't lose the hardware that comes with your case"

If you still have samples of some of the items, you can
measure them and find substitute materials. But a brass
standoff of the correct dimensions, would be like
"hens teeth", not easy to find.

Paul
  #26  
Old December 24th 19, 05:37 AM posted to alt.comp.hardware
Norm Why[_2_]
external usenet poster
 
Posts: 114
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."

[snippage]

What Length would work?
The trick is not to lose the hardware that came with the
computer case.

The standoffs are custom length, intended to elevate the
PCB to be flush with the slot holes for the I/O cards, in
the back. There's no way for me to guess any such measurement
from here. There are as many styles of solutions, as there
are days of the week.

If you artificially elevate the motherboard, with too-tall
standoffs, then your video card won't fit.

It's one of the items on the buyers list, to check the
fit and dress of standoffs before buying a computer case.
And that's pretty hard to do. You can't always inspect
this issue in advance.

I used to look at computer cases at a mom&pop (single store),
while they were in business. Basically, any store in town that
put computer cases on display in a useful way, went out of
business. And I did buy cases from them, so it's not like
the effort on their part wasn't rewarded.

For example, I don't buy "bump" style trays. That's where
the metal of the tray is formed into a bump of the appropriate
height, then a hole drilled, then the hole is threaded. While
it saves the manufacturer $0.0001 per hole, it doesn't do me
any good. Instead, I like the brass standoffs that have a
male thread on one end and a female on the other, then the
motherboard screw fits to fasten the board down. These have
a better controlled contact area where it touches the
ground ring on the motherboard.

In terms of "places that short", there was one Asus motherboard
where the plastic socket frame around the CPU socket, was
fitted *before* the soldering step. The plastic went through
a wave solder perhaps, and it swept up some solder
underneath the plastic (hard to inspect) and it
shorted out VCore. But that would only cause VCore
with a current limiter to trip off. And a little repair
work, you could find and remove the short.

But for direct rail shorts, sometimes there can
be a short inside the motherboard, but it's less likely
there is a short, say, right at the 24 pin connector.

Some Biostar motherboards, used to join the yellow 12V wires
on the 2x2 ATX12V, to the 12V wires on the main 24 pin connector.
This is not a good idea, and I have no idea why Biostar was
doing that. The 12VA and 12VB should be separate from one
another, in case some old PSU with actual separate transformers
for those two 12V was in usage. The 12V on the ATX12V 2x2, could
be a different 12V than the 12V on the main connector (fraction
of a volt difference).

Since you say you are observing a short with the ATX12V removed,
then this suggests something on the rails on the main 24 pin
is shorted. But I don't see a cosmetic root cause, because the
transfer of some of those rails around the motherboard, is on
a buried layer. The motherboards have 4,6, or 8 layers, with
6 layers used for RAMBUS boards, 4 layers for a lot of regular
DDR motherboards, and 8 layers reserved for sockets with
huge pincounts, where it's just too hard to route all the
signals using a limited number of layers. Somewhere in
that stack, can be some 2oz layers for routing power.

At work, we would use a bed-of-nails tester for evaluating
"ohms". After a board came off the line, sometimes tests
were done that way too (JTAG), which isn't all that common
in the computer industry. Those are known as structural tests.
A company like Asus, would use a camera and automation to check
for visible flaws (stuff in places it doesn't belong), can
use an Xray machine for BGA verification, but for electrical
test, there is only a 2 minute hand functional test
(lady plugs boards into mobo and runs some test code for
two minutes total time, then product goes in box). They
rely on statistical sampling for quality, rather than
every board being inspected with a magnifying glass. Every
board receives the 2 minute functional test, but other
steps are likely automated.

To visually inspect a square foot of PCB, takes about 2 hours
with a 10x magnifier, because I've done a few boards visually,
and you do find stuff. (That's where I found a certain brand
of resistors, with all the bodies cracked in half.) At one
time, Asus made 5 million motherboards per month, and there's
no time for that sort of inspection, and they can only
sample motherboards and inspect them for manufacturing
defects, then go back to the line and correct them. Not every
motherboard can be treated like a Rolls Royce.


Thanks Paul

From Google:

Thread: What size/kind of screws do I use for mounting motherboard?

Screw size depends on the size of the threads in the mobo standoffs,
usually M3x0.5 (metric) or #6-32 (US standard). I personally would not go
over 6mm or .25in in length. Head configuration is entirely up to you.
Most well-stocked hardware stores should have just about any size and
type you want.



Yes, that's the screw. But the length of the standoff and
what joins it to the motherboard, is up to the individual
computer case. The standoffs can be discrete brass items,
male threaded on one and and female threaded on top. And they
go into a flat tray metalwork which has threaded holes in
at least 9 standard places. Usually the tray has holes
drilled and threaded for several PCB standards.

But some trays dispense with the brass standoffs. Instead
of the metal tray being perfectly flat, it's formed so that
there are nine "bumps" in the metal, raised a certain height
above the plane of the rest of the metal. The bump has a threaded
hole in the top. This means they don't have to place nine
finely crafted brass standoffs in the box-of-hardware. And
I find the bump concept a bit worse, as the bump might be
less precise where it touches the motherboard (larger
footprint, in danger of exceeding the keep-out area around
the PTH plated through hole).

The height of the motherboard above the tray is "custom"
to a computer case design. This is why the brass standoffs
cannot be swapped from an Antec to a Compucase. You can see
that in the collection this guy has on hand, to take this picture.

"Various types of motherboard standoffs"

https://en.wikipedia.org/wiki/Comput...MGP5029_wp.jpg

( https://en.wikipedia.org/wiki/Computer_case_screws )

To me, in that picture, I think I'm seeing some
different diameter holes on the female ends of
the depicted standoffs. Compare the center three
brass items, to see how much difference there
can be in the screw choices. The head of the
motherboard fastener screw has to be small enough,
to stay within the keepout zone maintained by the
motherboard designer (the PCB has a multitude of
keepouts, like a square-ish pattern around the
CPU socket for the items placed on top of the CPU).

That's why my advice is:

"Don't lose the hardware that comes with your case"

If you still have samples of some of the items, you can
measure them and find substitute materials. But a brass
standoff of the correct dimensions, would be like
"hens teeth", not easy to find.

Paul


Thanks Paul,

As an aside. nylon MOBO screws might not be a bad idea. But for it to work,
I would be necessary to replace metal standoffs beneath the main board. One
the PCI VGA card is in place, there is direct connection to the frame.


  #27  
Old December 24th 19, 07:21 AM posted to alt.comp.hardware
Norm Why[_2_]
external usenet poster
 
Posts: 114
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."

"Don't lose the hardware that comes with your case"

If you still have samples of some of the items, you can
measure them and find substitute materials. But a brass
standoff of the correct dimensions, would be like
"hens teeth", not easy to find.

Paul


Thanks Paul,

As an aside. nylon MOBO screws might not be a bad idea. But for it to
work, I would be necessary to replace metal standoffs beneath the main
board. One the PCI VGA card is in place, there is direct connection to the
frame.


At this point, I have removed al but one MOBO screw (yikes), the 4pin 12V
connector and all PCI cards. I still get a 'short to ground' buzz on my
multimter. I shorted the CLEAR_CMOS. This is the worse it's ever been. I
think I am being informed of a ground loop that might generate hum in audio.

The ATX power cable pinout can be found he

https://en.wikipedia.org/wiki/ATX

The lines marked in blue are sense lines from the MOBO back to the PSU.
Imagine we had a male and female socket pair. Then we would be able to meter
the sense lines. We would be able to cut some sense lines that were causing
trouble. How dangerous and absurd is this idea? If it is not absurd then
someone may have thought of it first and there might be a product on the
market?


  #28  
Old December 24th 19, 08:07 AM posted to alt.comp.hardware
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini OnboardCase Buzzer Board Beep Alarm NEW."

Norm Why wrote:
"Don't lose the hardware that comes with your case"

If you still have samples of some of the items, you can
measure them and find substitute materials. But a brass
standoff of the correct dimensions, would be like
"hens teeth", not easy to find.

Paul

Thanks Paul,

As an aside. nylon MOBO screws might not be a bad idea. But for it to
work, I would be necessary to replace metal standoffs beneath the main
board. One the PCI VGA card is in place, there is direct connection to the
frame.


At this point, I have removed al but one MOBO screw (yikes), the 4pin 12V
connector and all PCI cards. I still get a 'short to ground' buzz on my
multimter. I shorted the CLEAR_CMOS. This is the worse it's ever been. I
think I am being informed of a ground loop that might generate hum in audio.

The ATX power cable pinout can be found he

https://en.wikipedia.org/wiki/ATX

The lines marked in blue are sense lines from the MOBO back to the PSU.
Imagine we had a male and female socket pair. Then we would be able to meter
the sense lines. We would be able to cut some sense lines that were causing
trouble. How dangerous and absurd is this idea? If it is not absurd then
someone may have thought of it first and there might be a product on the
market?


There is one pin with "remote sense". It is the 3.3V pin.
The remote sense is present, because of the relatively low
voltage of that pin. To do a good job of regulating
really low voltages, you use remote sense wires for the job.
It's better than sampling the voltage using a circuit inside
the PSU, as remote sensing measures the voltage as seen at the load.

A remote sense is typically a higher impedance feedback line.
It's not a power conductor and may use a slightly thinner
gauge of wire. This isn't an ATX supply, and this just
demonstrates the impedances involved. Maybe some bench
supplies for the lab are built this way.

FB+ ------- 1K ohms ------+
|
VCC -----------------------+-X Load

GND -----------------------+-X Load
|
FB- ------- 1K ohms ------+

The FB (Feedback) wires can't short anything,
because they have a series resistance. The
series resistance is small, compared to the
input impedance of the amp that picks
up the diff between FB+ and FB-. You need to take
the difference, in case the supply is "elevated"
or "floated" with respect to the load. The message
here, is the FB isn't hurting anything, can't
hurt anything, and *does not* need to be cut.
Also, if you break a feedback loop, by cutting
a feedback wire, the circuit will go "open loop"
and potentially rail, blowing up the load with an
excessive output voltage. (Um, don't to that, OK?)

When you're making these prognostications of yours,
remember that "capacitors", especially the large caps
used to provide bulk decoupling, they appear as a dead
short to the beeper on your meter. This is why ohming
out an item like that (a mobo rail) can give a deceiving result.

This is why I mentioned my clamp-on ammeter, which makes
current measurements without disturbing any conductors.
It works a treat on the older systems where the wires
have all the right colors, and it's visually easier to
grab all the wires-of-same-color and put them in the
jaws of the clamp-on DC ammeter. Then, you get a total
current reading, and you can use your knowledge of motherboard
design era, to figure out whether the current value measured
is reasonable or not.

My clamp-on ammeter also has a "peak detect", and can capture
the top current flow value over a period of time. When my
previous car had a starter problem, I wanted to measure the
current, and by setting the clamp-on meter to "peak detect",
I was able to determine it drew as much as 150 amps from the
12V battery. Using a second regular-multimeter with
trough detection, I got a snapshot of 9V as the lowest value
while the battery tries to turn the car over and start it.
Using these values, you get some idea of the impedances involved
(3V drop/150 amps, in ohms, or about 20 milliohms). My clamp-on
ammeter can measure up to 400 amps, and for motherboard work,
I set it to 40 amps full scale. An Athlon motherboard can draw
up to 25 amps from +5V, as an example of a pretty high current
reading from that era. Modern motherboards aren't even close to that.

Since the power supplies now are sleeved and the wires are
all black in color, this has put a big damper on my measurement
fun. I must use my 24 pin to 24 pin extension cable (which
has loose wires), to gain access to the wires to make a
current flow measurement. Then I don't have to cut the sleeving
to get at individual wires.

By measuring current flows, i can avoid being deceived by
the multimeter "buzzer" trying to charge up capacitors.
This could inadvertently show something as shorted, which
is not shorted. Instead, I measure current flows to get some
idea whether a load is abnormally high. Because I don't
cut any conductors to insert a measurement shunt, and the
meter uses magnetic fields for the measurement, it's possible
to quickly review the loading (one rail at a time) as a
diagnostic procedure.

The clamp-on DC ammeter cost me around $300, years ago,
and I don't know how much those have dropped in price
since. My regular-multimeter was $100, and it has
an RS232 output for recording readings on a PC. The RS232
output is optoisolated, so voltages you're working on,
cannot jump the RS232 interface and blow up your computer :-)
I think that's pretty neat, and is one of the reasons
I spent $100 on a multimeter, rather than about $20 for a
HarborFreight one.

I don't have a lot of test equipment, and that's the
best of what I've got. I don't own a scope.

Paul
  #29  
Old December 25th 19, 11:58 PM posted to alt.comp.hardware
Norm Why[_2_]
external usenet poster
 
Posts: 114
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."


As an aside. nylon MOBO screws might not be a bad idea. But for it to
work, I would be necessary to replace metal standoffs beneath the main
board. One the PCI VGA card is in place, there is direct connection to
the frame.


At this point, I have removed al but one MOBO screw (yikes), the 4pin 12V
connector and all PCI cards. I still get a 'short to ground' buzz on my
multimter. I shorted the CLEAR_CMOS. This is the worse it's ever been. I
think I am being informed of a ground loop that might generate hum in
audio.

The ATX power cable pinout can be found he

https://en.wikipedia.org/wiki/ATX

The lines marked in blue are sense lines from the MOBO back to the PSU.
Imagine we had a male and female socket pair. Then we would be able to
meter the sense lines. We would be able to cut some sense lines that were
causing trouble. How dangerous and absurd is this idea? If it is not
absurd then someone may have thought of it first and there might be a
product on the market?


There is one pin with "remote sense". It is the 3.3V pin.
The remote sense is present, because of the relatively low
voltage of that pin. To do a good job of regulating
really low voltages, you use remote sense wires for the job.
It's better than sampling the voltage using a circuit inside
the PSU, as remote sensing measures the voltage as seen at the load.

A remote sense is typically a higher impedance feedback line.
It's not a power conductor and may use a slightly thinner
gauge of wire. This isn't an ATX supply, and this just
demonstrates the impedances involved. Maybe some bench
supplies for the lab are built this way.

FB+ ------- 1K ohms ------+
|
VCC -----------------------+-X Load

GND -----------------------+-X Load
|
FB- ------- 1K ohms ------+

The FB (Feedback) wires can't short anything,
because they have a series resistance. The
series resistance is small, compared to the
input impedance of the amp that picks
up the diff between FB+ and FB-. You need to take
the difference, in case the supply is "elevated"
or "floated" with respect to the load. The message
here, is the FB isn't hurting anything, can't
hurt anything, and *does not* need to be cut.
Also, if you break a feedback loop, by cutting
a feedback wire, the circuit will go "open loop"
and potentially rail, blowing up the load with an
excessive output voltage. (Um, don't to that, OK?)

When you're making these prognostications of yours,
remember that "capacitors", especially the large caps
used to provide bulk decoupling, they appear as a dead
short to the beeper on your meter. This is why ohming
out an item like that (a mobo rail) can give a deceiving result.

This is why I mentioned my clamp-on ammeter, which makes
current measurements without disturbing any conductors.
It works a treat on the older systems where the wires
have all the right colors, and it's visually easier to
grab all the wires-of-same-color and put them in the
jaws of the clamp-on DC ammeter. Then, you get a total
current reading, and you can use your knowledge of motherboard
design era, to figure out whether the current value measured
is reasonable or not.

My clamp-on ammeter also has a "peak detect", and can capture
the top current flow value over a period of time. When my
previous car had a starter problem, I wanted to measure the
current, and by setting the clamp-on meter to "peak detect",
I was able to determine it drew as much as 150 amps from the
12V battery. Using a second regular-multimeter with
trough detection, I got a snapshot of 9V as the lowest value
while the battery tries to turn the car over and start it.
Using these values, you get some idea of the impedances involved
(3V drop/150 amps, in ohms, or about 20 milliohms). My clamp-on
ammeter can measure up to 400 amps, and for motherboard work,
I set it to 40 amps full scale. An Athlon motherboard can draw
up to 25 amps from +5V, as an example of a pretty high current
reading from that era. Modern motherboards aren't even close to that.

Since the power supplies now are sleeved and the wires are
all black in color, this has put a big damper on my measurement
fun. I must use my 24 pin to 24 pin extension cable (which
has loose wires), to gain access to the wires to make a
current flow measurement. Then I don't have to cut the sleeving
to get at individual wires.

By measuring current flows, i can avoid being deceived by
the multimeter "buzzer" trying to charge up capacitors.
This could inadvertently show something as shorted, which
is not shorted. Instead, I measure current flows to get some
idea whether a load is abnormally high. Because I don't
cut any conductors to insert a measurement shunt, and the
meter uses magnetic fields for the measurement, it's possible
to quickly review the loading (one rail at a time) as a
diagnostic procedure.

The clamp-on DC ammeter cost me around $300, years ago,
and I don't know how much those have dropped in price
since. My regular-multimeter was $100, and it has
an RS232 output for recording readings on a PC. The RS232
output is optoisolated, so voltages you're working on,
cannot jump the RS232 interface and blow up your computer :-)
I think that's pretty neat, and is one of the reasons
I spent $100 on a multimeter, rather than about $20 for a
HarborFreight one.

I don't have a lot of test equipment, and that's the
best of what I've got. I don't own a scope.

Paul


Thanks for the advice. I have re-installed all metal MOBO screws with labor.
All my work with a Multimeter buzz for short, was useless. I shook assembly
and one screw came out. It is amazing what's to be found when one's nose is
face down in rug.

I removed, tested and re-installed the 3.3V CMOS battery. I have
re-installed all useful connectors, even the speaker beep connector.
Computer stills shuts down immediately - no beep codes, now.

My problem is worse than when I began. If I am not to blame, maybe there is
blown capacitor? I thought Gigabyte used plastic film caps. Maybe that came
later? I have looked at the caps and none are exploded. However when I
search the board, I see a cap with + nearby suggesting it is electrolytic. I
have intermittence problems with xBox 360 and Samsung wide screen with my be
due to keep caps. I am unable to find gibabyte circuit diagram.

Because they are numerous, maybe I should replace all with ceramic, plastic
film or tantalum? WWW says shelf life of electrolytic capacitor is two
years. After 11 years storage they are discharged. Maybe if I could use
external 5V supply, the caps could be repolarized. Where do test resistance
so I don't start a fire?


  #30  
Old December 26th 19, 12:50 AM posted to alt.comp.hardware
Paul[_28_]
external usenet poster
 
Posts: 1,467
Default "Speaker For PC Interanal BIOS Computer Motherboard Mini Onboard Case Buzzer Board Beep Alarm NEW."

Norm Why wrote:


Thanks for the advice. I have re-installed all metal MOBO screws with labor.
All my work with a Multimeter buzz for short, was useless. I shook assembly
and one screw came out. It is amazing what's to be found when one's nose is
face down in rug.

I removed, tested and re-installed the 3.3V CMOS battery. I have
re-installed all useful connectors, even the speaker beep connector.
Computer stills shuts down immediately - no beep codes, now.

My problem is worse than when I began. If I am not to blame, maybe there is
blown capacitor? I thought Gigabyte used plastic film caps. Maybe that came
later? I have looked at the caps and none are exploded. However when I
search the board, I see a cap with + nearby suggesting it is electrolytic. I
have intermittence problems with xBox 360 and Samsung wide screen with my be
due to keep caps. I am unable to find gibabyte circuit diagram.

Because they are numerous, maybe I should replace all with ceramic, plastic
film or tantalum? WWW says shelf life of electrolytic capacitor is two
years. After 11 years storage they are discharged. Maybe if I could use
external 5V supply, the caps could be repolarized. Where do test resistance
so I don't start a fire?


The service life of electrolytic capacitors is 17 years
(from the webpage of Illinois Capacitor).

At the 17 year point, the rubber seal in the bottom can
dry out. However, I have a motherboard which is close
to 20 years old, and it still works.

Electrolytic capacitors with an internal pH problem, the
liquid inside will eat through the casing of the capacitor
in as little as two years. This is a defective product,
plain and simple. The electrolytic formula was a "stolen"
chemical formula, where the buffering agent was missed.
Some materials were supposed to be added to stabilize the
liquid and make it compatible with the materials around it.

Electrolytic reliability is proportional to temperature.
At 105C or greater temperatures, the life of some caps
is listed as short as 2000 hours. But modern designs, and
the recommended computer air temp of no higher than
35C to 45C or so, and the exponential in the reliability
math equation, ensures the life is many times 2000 hours.
The reliability formula is a curve-fitted Arrhenius
equation. Normal liquid chemistry reactions, the Arrhenius
rate doubles for every 7C. On capacitors, the curve fit
to the reliability data, has a doubling of rates every
15C or so. So while in chemistry class, we're taught
there is just one coefficient for that exponential,
electrical engineering shows that many items follow the
general form of the relationship, except the coefficient
needs to be curve fitted to the data. Between 45C and 105C
would be 60C or four doublings or a factor of 16. So instead
of 2000 hours, we'd get 32000 hours. And the only time
a PC is 45C, is in summer, with the AC turned off. The time
is even larger than that, because of the chilled temperatures
in winter months.

When working with plane-to-plane shorts inside PCBs, those can be
hard to find. You would, at the very least, remove all components
and carry out a visual inspection, as a starting point. And
a bench magnifier, to make things a bit bigger, helps at
a time like that. In two places I worked, we had a binocular
microscope (maybe $2000 to $3000 or so), which was a great
aid for stuff like that. You don't need too much magnification.
It's not a job for "oil immersion" or the like. (I think
the strongest microscope I've used, was 1200X or so, and used
oil immersion to some cover slips for biology work. The objective
was spring loaded because... students. You can easily crush the
glass while adjusting one of those.) PCB inspection is fine
at around 10X.

If the flaw is inside the PCB, you won't spot that visually
unless the board heats up and a burn mark appears on
the surface. The worst computer motherboard failure I've ever seen,
a ring was "charred" all the way around the CPU socket. That's
a VCore-related failure, where the current limiter didn't work properly.

Paul
 




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