Once in a while we get a machine into the workshop for repair that turns out to be a real head scratcher. One such unit was collected from a customer last week and it has taken a while to get to the bottom of it. It was a Dell Inspiron 530 that failed to post when powered up. The fans would spin and the power light would remain steady amber indicating a problem with either the power supply unit or motherboard.
We first swapped out the PSU for a known good one, but the symptoms remained the same. Since the PC was 2 1/2 years old the customer and the customer did not want to spend much on the repair we figured that a replacement motherboard would be outside the customer's spend. Just to be on the safe side we checked the warranty status with Dell by entering the unit's service tag number in their support site and we were pleasantly surprised (as was the customer) to find that there were 155 days remaining of a three year warranty. So we called in Dell to do the repair.
A Dell contract technician arrived with a replacement motherboard, swapped the old one for the new one and, voila, the same symptoms persisted. The technician contacted Dell again and it was deemed that the problem was a faulty input/output panel switch which was duly ordered. The next day the technician reappeared with the part, fitted it and, again no change in the symptoms. At this stage he started to suspect the power supply but I told him that we had already checked with a known good PSU. He asked if I had a good PSU we could try so we hooked one up and, lo and behold, the unit posted. So the technician concluded that both the original PSU and motherboard had failed simultaneously - a reasonable conclusion under the circumstances.
To update service tag number associated with the new motherboard the technician needed to reboot the unit and enter the BIOS. Unfortunately, as soon as he rebooted the original symptoms returned. A this point he surmised that the PSUs were blowing due to a possible short in the motherboard/case. However, I brought the PSU that was connected and the original PSU still in the case and mounted them in a Dell Dimension on the work bench - in both cases the unit booted without problems, ruling out the PSU as a problem.
At this point there was, understandably, much head scratching going on and DELL HQ was again contacted by the technician. The conclusion was that another new motherboard and a new PSU would be dispatched in an attempt to resolve the problem. And they duly arrived this morning along with Tony the technician who replaced the parts and, much to his dismay, the same problem arose. The only thing that hasn't been changed at this point is the processor. So Tony (we're on first name terms now) called in again to Dell and the next step is they are taking it in to their repair facility next Monday for a 6-8 day stay. I'll take the hard drive out before they collect it to make sure the customer's data stays intact. Will keep you posted on progress.