My son's 3-month old desktop computer failed and upon troubleshooting it, I\nfound that the thermistor (TH1) that is in series with a 6.3A glass fuse and\nlocated in the 120VAC input power feed inside the power supply module had\nself-destructed. I tested the soldered in fuse and it was still good, so\nassume that it did not fail due to an over current situation. To determine\nconclusively that the failure did not result from a PSU secondary problem, I\ntemporarily bypassed (shorted) the blown device with a jumper. When I did\nthis the PSU and computer came up normally so I conclude that this is an\nisolated failure, possibly due to an under-designed component in a cheap\nimported PSU that came in the tower unit he built. (I believe it is a 600W\nPSU and the computer is pretty lightly loaded without many peripherals, so\nthat is why I suspect it just being infant mortality, or possibly an\nunder-designed part in this design).\n\nI know that the purpose of the device is to limit the start up inrush\ncurrent to the PSU and protect down stream devices, so I definitely ant to\nreplace it. Unfortunately, I'm not sure yet what the local Radio Shack will\nstock and wanted to know in advance what generic substitutes I might be able\nto use for this purpose.\n\nBasically, what I am asking is how do I read the 5D-9 value that was stamped\non the old part? Is there a current rating and if so was the old part\nconsistent with the 6.3A fuse or was it undersized and that is why it failed\nafter just 3 months of use? Does the "5" in the first part of the rating\nindicate the resistance in ohms and if so, is this the steady state value or\nat the start up/inrush?\n\nKnowledge on the part nomenclature, reliability, and use in a SMPS is\ndesired. Suggestions on suitable replacement parts that will prevent this\nfrom occurring again are welcome. Thanks in advance.\n\nBob S.