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what's your recent fail?

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harerod:
nctnico, thanks for the feedback. Just my observation: for series production, the PCB has to be optimized for the actual manufacturing process. The structures on the PCB plus the components must fit the solder profile. The series manufacturer will try to improve troughput by using the shortest time profile possible.
I see a similar thing with certain cable harness manufacturers, who turn the solder temperature way up, to reduce solder time.

A prototype manufacturer has most of the overall effort in setting up the production, so they  can take it easier on the speed. Tombstones are nonexistent when I solder with my lab equipment, rare with prototype manufacturing, but will appear in in series production.

I prefer to run prototypes in the series process. Since other restrictions apply (budget, time), I can rarely do this nowadays.

David Hess:

--- Quote from: exe on May 03, 2021, 06:29:33 am ---
--- Quote from: David Hess on May 02, 2021, 07:18:13 pm ---After several days of randomly changing various things with no positive result, I was inspired to leave it powered up, and after several more days it POSTed.  Now it reliably POSTs, so far.
--- End quote ---

That's weird but... When I worked in a datacenter I had similar issues with motherboards that at first appeared to be dead. Like, I remember after a power outage I had to repair a very old server, in a crudely-made enclosure (replace and hdd or something like that). I dropped a screw on the motherboard. The server shut down itself immediately and denied to start again. Worse yet, I didn't have spare parts for old piece of junk it was. Lucky me, somehow it started after 15 minutes after tens of attempts to boot it.
--- End quote ---

I have no explanation yet and it took a couple days before it POSTed.  I will be installing Windows 7 on it and maybe it will fail again with some indication of what is going on.

AlfBaz:

--- Quote from: David Hess on May 07, 2021, 11:51:12 pm ---
--- Quote from: exe on May 03, 2021, 06:29:33 am ---
--- Quote from: David Hess on May 02, 2021, 07:18:13 pm ---After several days of randomly changing various things with no positive result, I was inspired to leave it powered up, and after several more days it POSTed.  Now it reliably POSTs, so far.
--- End quote ---

That's weird but... When I worked in a datacenter I had similar issues with motherboards that at first appeared to be dead. Like, I remember after a power outage I had to repair a very old server, in a crudely-made enclosure (replace and hdd or something like that). I dropped a screw on the motherboard. The server shut down itself immediately and denied to start again. Worse yet, I didn't have spare parts for old piece of junk it was. Lucky me, somehow it started after 15 minutes after tens of attempts to boot it.
--- End quote ---

I have no explanation yet and it took a couple days before it POSTed.  I will be installing Windows 7 on it and maybe it will fail again with some indication of what is going on.

--- End quote ---

I've just finished having similar issues.
My original rig died which required me to purchase a new power supply and motherboard. I had to go 2nd hand with the mother board so I didn't have to buy a new cpu.

The board would not power up after switching the power supply off or unplugging it. You have to wait several minutes after applying power to the psu before the power button would work.

I did some probing with the aid of a boardview file and found the 3VSB (standby) rail had a massive low frequency ripple from 3V to 1V at first and after some minutes it would stabilize to a solid 3V. At that stage it would work.

Initially I though it had something to do with the cmos battery which measured 3V but would drop to less than a volt if you loaded it with a handfull of mA's.
I replaced said battery and nothing changed.

I suspect a fault with the board somewhere that needs something to charge before the 3V rail comes good.

In this board the 3VSB rail is used to apply logic levels to the "super I/O" chip which handles pulling the psu's pwron pin low

David Hess:

--- Quote from: AlfBaz on May 08, 2021, 12:54:22 am ---I've just finished having similar issues.
My original rig died which required me to purchase a new power supply and motherboard. I had to go 2nd hand with the mother board so I didn't have to buy a new cpu.

The board would not power up after switching the power supply off or unplugging it. You have to wait several minutes after applying power to the psu before the power button would work.

I did some probing with the aid of a boardview file and found the 3VSB (standby) rail had a massive low frequency ripple from 3V to 1V at first and after some minutes it would stabilize to a solid 3V. At that stage it would work.

Initially I though it had something to do with the cmos battery which measured 3V but would drop to less than a volt if you loaded it with a handfull of mA's.
I replaced said battery and nothing changed.

I suspect a fault with the board somewhere that needs something to charge before the 3V rail comes good.

In this board the 3VSB rail is used to apply logic levels to the "super I/O" chip which handles pulling the psu's pwron pin low
--- End quote ---

I checked the voltages from the original power supply and found no problems, but changed the power supply anyway and it still did not work.  Then I messed with the CMOS battery and resetting the CMOS data without effect.  It finally POSTed after being left on for days and that was without the CMOS battery, but I have since put a new CMOS battery in and it still POSTs.

What I have not done is left it off since it first started POSTing again, but eventually that will happen.

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