Norm Why wrote:

Thanks Paul,

I messed around with temperature enough. The MOBO has been recycling in a
hot room. The infrared thermometer allows me to do controlled but
pointless experiments with a hairdryer. I have now taken some voltages.
Where I removed a 470 uF 16V capacitor allows me to measure 12V rail. It
goes up to 12V steady each cycle. The vacant PCI slot allows me to measure
5V again. Now it shows 0V, no 5V. No 5V explains the beep codes:

Q: What do the beeps emitted during the POST mean?
A: The following Award BIOS beep code descriptions may help you identify
possible computer problems.
(For reference only.)
1 short: System boots successfully
2 short: CMOS setting error
1 long, 1 short: Memory or motherboard error
1 long, 2 short: Monitor or graphics card error
1 long, 3 short: Keyboard error
1 long, 9 short: BIOS ROM error
Continuous long beeps: Graphics card not inserted properly
Continuous short beeps: Power error

No 5V is a major power error. But why now?

Let me elaborate. The infrared thermometer says there is no short circuit.
The E4700 is cold. The literature says the maximum temperatures for the
Intel P45 and the ICH10 I/O controller hub are well over 100 C. With a heat
gun, I carefully raised the temperature of their heat sinks to 50C. Still no
POST. End of silly experiment. There is no way the chips were damaged.

I guess I need to find out why 5V is not delivered to rail. I'm an old man.
I need to lie down and sleep.

Your board either has a 20 pin or a 24 pin "main" power connector.

Place the ground of your multimeter on an I/O screw on the back panel.
I like to clip the black probe to a screw, so I only need one hand
to make measurements with the red probe.

The ATX main power connector, you can probe in the back of the
connector, and just barely touch the metal on each wire crimp in
there. This allows every voltage on the connector to be verified.
As long as an older power supply is used, it has nice colored wire
and this makes it easier to determine which rail each wire is
connected to.

If you scroll down to 50% of this web page, there's a table of wire colors.

http://www.playtool.com/pages/psucon...onnectors.html

PWR_OK gray Pin 8 || || Pin 20 white -5 volts (optional) === "blank pin"

You can see in that example, every wire has a color like gray or
white or red or orange. And for the ATX supplies that adhere
to the standard, this makes debugging a lot easier. I have a newer
PSU with all-black wires and that's nothing but a pain in the ass.

This kind of extension cable can be added to the power path, if
you need some "wire colors" for inspiration. I might use something
like this with my all-black-wire PSU, during a debug session.

https://www.newegg.com/p/N82E16812198008

Paul