PC problems

Hi John...

Sure sounds like a problem in the first 64k memory to me...

Check the contacts on the mem itself, maybe clean them up gently... and take a good luck at the contacts on the motherboard; maybe blow the dust off them if any.

Take care.

Ken

I have had cases where a RAM may fail the diagnostics in one machine, and then work okay in another. There may be a slight difference in the clocking rates that one machine is more sensitive to than the other, or something like that.

If you get a bad indication of the RAM, it is best to replace it, and not take a chance.

--

Jerry G. ======

Problem 1. The PC is becoming more difficult to boot. More often than not it fails POST, the result being no video signal and looping through an indefinite sequence of single beep and FDD activity. The only way out is to keep trying either the Reset Button or Power button. The BIOS is AMI on a PCCHIPS MoBo M538LMR.

Problem 2. In looking for the above fault I ran memory diagnostics and found that one of the two DIMM's (128MB PC133 SDRAM) was failing on a single bit. However, removing this DIMM (leaving a single 128MB PC100) did not affect the booting problem. Strangely the dodgy DIMM works perfectly in another PC!

Once the system is booted it works reliably (except for its dislike of one bit of the now removed memory stick)

TIA John

Thanks for the response Jerry G. So the RAM should be considered suspect. Any ideas on the intermittent booting problem. Sooner later the PC probably won't boot at all and I would like to diagnose before then.

John

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Thanks for the response Jerry G. So the RAM should be considered suspect. Any ideas on the intermittent booting problem. Sooner later the PC probably won't boot at all and I would like to diagnose before then.

John

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You might be experiencing the bad caps syndrome. I had a MB that would occasionally freeze, then it got harder to get it to boot. I tried all the standard stuff and finally realized that I had 15 bad electrolytic caps. Replaced them and been running fine since. Look for caps with bulged tops or a brown dot in the center of the top. Also watch for brown stuff running down the board.

WT

Thanks or the suggestion. Will have to do some dismantling and have a look.

John

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Look closely at the motherboard, are any of the electrolytic capacitors bulging or leaking?

I've seen similar problems caused by bad motherboards, hard drive, CD-ROM, RAM, and power supply, in short just about any major component can cause it to fail POST, not always in obvious ways.

On Mon, 21 Mar 2005 18:21:29 -0000, "John" put finger to keyboard and composed:

It may allow the other PC to boot, but does it pass the same memory diagnostics in that machine?

- Franc Zabkar

Apologies for the delay in answering your question Franc (Please see below)

My current guess, based on the various replies (thanks all) is that the mobo has some poor caps affecting in particular the RAM area.

Can these mobo caps behave like dried-out PSU caps, which can improve as repeated pulses "warm" them up? If so this could explain why POST is very unreliable, but once passed the PC can run reliably.

Another piece of evidence is that although one of two fitted memory DIMM'S failed repeatedly with only one bit, when I tried with only the failing DIMM fitted there was initially a burst of other memory failures before settling to the previous one bit failure. I didn't repeat these tests but maybe there are caps on the non-failing DIMM which help-out the more marginal one?

BTW as I don't have any soldering kit for surface mount, is there any future in trying to add some caps with short leads?

TIA

John

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On Thu, 24 Mar 2005 20:52:53 -0000, "John" put finger to keyboard and composed:

Do you mean that your memory sticks have caps on them?

You should be able to desolder the smt caps with a fine tipped iron. Clean up the pads and then solder a low profile miniature leaded aluminium electrolytic directly to the pads.

However, before trying this, I'd make absolutely sure that's where your problem lies. AFAIK, current motherboards generally have onboard regulators supplying the DIMM slots.

- Franc Zabkar