MB won't even attempt POST

[freeportd]

Well, I sweated a bunch - and got concerned about cold joints - but prior practice was valuable getting through this. The caps around the memory was tough to remove. The stainless steel pick idea on clearing holes was very valuable.

At first, I thought it was bad as I received C1 on second boot (first one was OK). But it turned out to be RAM that wasn't seated properly. This board is great!

I did it!

freeportd

[freeportd]

MB won't even attempt POST

Hi there,
I recently recapped my Epox 8rda+ motherboard, put things back together - and things have been working fine (except issue with C1 POST error - which a reseat of RAM resolved).

After about two weeks of a happy family, the PC now refuses to power up. The fans just twitch - and then don't move. MB doesn't even attempt a POST - so no codes in my LED.

I've read a few of the other postings about checking switch, verifying voltage and such (and I'll do those steps), but what would cause this to fail all of a sudden. Can I assume my new caps are OK because they ran for over 2 weeks?

Any suggestions welcomed. Thanks, freeportd

[willawake]

Re: MB won't even attempt POST

did you try another psu?

[Tom41]

Re: MB won't even attempt POST

I experienced something like that with a defective PSU - I could hear a sort of 'sparking' noise in the PSU, and there wasn't enough power coming through to move the fans more than a few mm. I'd say either your PSU is at fault, or there's a short in the wiring somewhere.

Have you tried powering up the motherboard with nothing else (HDDs, floppy drives, CDROM) connected to the PSU? My problem turned out to be vented caps in the PSU, which were shorted - hence the sparking. Getting a new PSU fixed it.

[willawake]

Re: MB won't even attempt POST

if it does that with a known good psu then you have big probs which i doubt have arrived from the recapping.

i have seen that also with a floppy drive that became fucked up. powered up fine once power was removed from the floppy.

[freeportd]

Re: MB won't even attempt POST

Wow, you guys are fast. I checked with another (known) good PSU and similar situation. But, my VOM yields the following:

Pins 1 through 20 on the ATX connector (on the MB) look relatively OK per other posts. By that, I show all ground connections with zero resistance to each other. The pins with power all show some sort of (increasing) resistance as I connect one lead to ground and the other to the respective pin. I'm assuming that's a cap as it's charging - thus increasing resistance to circuit between probes.

However, pin 18 shows infinite resistance. I've checked that with both an analog and a digital VOM - and both show same thing - infinite. Shouldn't I see something there?

Well, to save time - I just tried removing floppy connector - hit the power button and wham - the CPU fan is spinning like crazy!! Of course, I've got the RAM, video, and processor out right now...so no boot up - but the LED shows FF (which is normal for 8rda+). Willawake, you are a savior.

I'll report back soon once all the pieces/parts are restored (PS is hanging out of back, CPU off to the side, RAM, video, etc).

Thanks a bunch - you folks are great!

[freeportd]

Re: MB won't even attempt POST

Well, not there yet...I powered down by holding the power button for 4-5 seconds, repeated a few times and all looked good. My wife then reminded me that once the computer booted, it was fine until she turned off the power strip to the PS at the end of the day. So, I turned off the toggle on the back of the PS, waited a few seconds, turned it back on....and now it's back to the same state...no power on.

Also, when it did work as just reported in previous post, the first press of the power button didn't do it...a second push then launched it. I'll verify that the switch is OK but wanted to get this reposted. Drats, thought I was done - as I don't care about floppies...

[freeportd]

Re: MB won't even attempt POST

Well, I just verified that the switch (power on) is OK.

So, what's going on with this MB? It's OK once it's booted once...and then I don't remove power to it...but once I do....

freeportd

[willawake]

Re: MB won't even attempt POST

how old are these psus? sounds like badcaps in the psu. can you open them up to take a look.

the first press of the power button didn't do it...a second push then launched it.

this can be sign of badcaps, its warming up on the first try. unlikely button is intermittently working.

[freeportd]

Re: MB won't even attempt POST - more info

Well, I've done more multi-meter work - here's the info:

When PSU rocker switch is on (1), the voltages observed by pin number are:

1) .01 2) .01 3) n/a 4) .97 5) n/a 6) .97 7) n/a 8) .03 9) 5.11 10) .04

11) .01 12) .00 13) n/a 14) 4.05 15-17) n/a 18) .00 19) .97 20) .97


I also checked pin 8 (PwrOK) while PS rocker=1 and power button pressed - no change in voltage (stays at .03).

I then checked pin 14 (ps-on) while pressing power button - it stays at 4.05.

I'm guessing it's the latter that prevents my power up. Suggestions?

thanks, freeportd

[freeportd]

Re: MB won't even attempt POST

how old are these psus? sounds like badcaps in the psu. can you open them up to take a look.


this can be sign of badcaps, its warming up on the first try. unlikely button is intermittently working.

It's a brand new unit. Also tried with a different known-good PS and same results. The known-good PS was recapped by yours truly - and later confirmed working in another working system. So, unlikely that (two) PS are bad.

I've replaced all caps of 1000 uF or greater. See my prior post - pin 14 is showing 4.05v - seems wrong to me if I'm hoping to see the PSU spin up...

[freeportd]

Re: MB won't even attempt POST

In the hopes that it might help someone else, I resolved this by removing the CMOS battery and replacing. Not sure why that helped, but it did. Consistent powerup is gratifying!

freeport

[andy1234]

Re: MB won't even attempt POST

You cleared the CMOS when you pulled the battery out. Not all no post motherboards come from bad caps. I've seen boards that boot from one CPU and won't boot from others of the same family IE P3 but with either 66/100/133 FSB even though the bios supports all 3 and the jumpers are set correctly. Bad CPU sockets can cause similar problems. If you want to get into M/B repair even part-time you'll need a few things.

1 power supply tester ( and not the cheapos, you want one with decent load resistors so you can run the PSU for a bit to test)

2 A decent PCI post card ( and a spare for when the first one cooks due to bad rail voltages!)

3 ESR meter, a good capacitance meter,multimeter ( and if you do more than a cfew boards, a metal brush end for continuity checks) to find where all the runs on the PCB go.

4 Eeprom flasher There are a few you can get that do most bios chips for >$50.00.

5 If you are really serious an oscilloscope for checking data rails!

^ A full beer fridge for the days nothing seems to be working !

[starfury1]

Re: MB won't even attempt POST

This is interesting
So after you cleared the CMOS it booting first time every time regardless of any conditions outlined above?

Secondly did you reset,clear cmos to bios defaults after recapping and rebuilding the system?

just wondering

[freeportd]

Re: MB won't even attempt POST

Basically, I removed and replaced the battery (which does clear the CMOS - as it keeps it 'alive' when power is off). Once battery replaced, I've not had a single problem since. I did have the initial boot show a CMOS 'failure' message - but that's expected after clearing CMOS. Since then the board's been fine. I'm happy!

[bgavin]

Re: MB won't even attempt POST

I have seen this problem on a number of my clients' machines.

Something in the ATX power supply gets crowbar'ed for some reason. I use the Antec PSU tester to reset the PSU, and then it works correctly.

[RoadWarrior]

Re: MB won't even attempt POST

In the hopes that it might help someone else, I resolved this by removing the CMOS battery and replacing. Not sure why that helped, but it did. Consistent powerup is gratifying!

freeport

I've seen that. Boards that won't POST with a bad or absent CMOS battery.

[brbpab94]

Re: MB won't even attempt POST

I thought I read someware that your suppose to reset the comos after a recap.

[Topcat]

Re: MB won't even attempt POST

I thought I read someware that your suppose to reset the cmos after a recap.

It's not required, but it's a good habit to get into. I've seen bad caps cause corrupt CMOS data, resulting in some really strange problems. On top of that, theres nothing more annoying than recapping a board and the owner/customer has a BIOS password on it. Out comes the CMOS battery and tyhe clear CMOS jumper gets closed.... Let it sit a few minutes, and shazam! Occasionally, a customer will email me asking why the password was gone.... Umm... If they really need that one answered....