Im working on a Compaq n610c laptop. It runs fine off of AC power.\nWhen I remove the AC cable there is a distinct squeal coming from the\ncomputer. I have disassembled it and found that the squeal was coming\nfrom the area of the DC-DC converter which is mounted right above the\nprocessor. I replaced the DC-DC converter board, but the problem is\nstill there. To further describe this strange issue, when the battery\nis in and the computer is not turned into the on position, there there\nis a quieter high frequency clicking sound. When the power is turned\non there is a distinct squeal. Its not coming from any discernably\nmoving parts. Any help would be appreciated. Thanks!