Webster wrote:The only question left in my mind is what effect wetting the compression joints with some solder would have.
All people need to think about is their old Nintendo. Remember cleaning the cartridge with a pencil eraser?
Or an older stereo. Turn the volume knob up and hear "pop pop pop?" Time for some contact cleaner!
Remember how your slot car race track came with the little piece of Scotch-Brite?
zepper wrote:What contacts at the ATX connector have most often overheated and caused melted wires and shells? 12V - no, 3.3V - no, 5V - YES!!! So why are we testing at 12V? The reason for using 12V for so many things now is to reduce the necessary current load per wire/contact. And almost nothing in the PC uses 12V directly anyway - it is always reregulated and filtered down to a much lower voltage. Only drives and fans use the 12V directly. So the actual 12V number is almost irrelevant. When CPU power is taken from 5V, the Amps go way above 11 - but not all on one wire, of course.
zepper wrote:And I'll mention here that most switching PSUs require a minimum load for accurate regulation. That explains the anomalies JG saw at 0 load. Anyone that knows SwPSUs at all should know that... The minimum load on +12 and +5 should be 2 Amps for most. Some older SwPSUs can actually be damaged if run with 0 load - most newer designs have zero load protection. Better case/PSU combos and barebone systems were (back in the day) delivered with dummy loads connected to the PSUs to prevent just such an occurrence.
The main ATX connector and 8-pin EPS connector are hooked up and there is already an 11A load on the +12V leads of these connectors. There is also a 12A load on the +3.3V rail, 15A load on the +5V rail, 2A load on the +5VSB and 0.5A load on the -12V. In other words, the power supply is running with a 250W load on it as if it were plugged into a computer.
What I do from here is gradually increase the load on the PCI-e connector from 0A to 5A to 7A to 9A to, finally, 11A, record the voltages with the DMM and log them in Excel.
zepper wrote:What about the gauge (not gage )
zepper wrote:...of the wires on the PSUs? Some PSU makers have gone to 20 or 22 gauge for a lot of the wires. Better made PSUs will have 18 ga. for most high-current circuits. Even so, in the one case where the wire seemed to drop voltage, it would more likely be the crimp connection (or faulty stripping - I've actually found wires totally broken inside the insulation from poorly adjusted strippers) than the wire itself. At the lengths mentioned here, even 22 ga. shouldn't drop much at all as long as none of the strands were lost or broken in the stripping/crimping.
zepper wrote:The problem with modular is not when new, but after many cycles of heating cooling the wires and contacts as well as multiple more opportunities for bad crimps/strips. The cheap contacts used on PSUs (seldom genuine Molex or Amp - generally some oriental knock-offs) these days will loosen more with heat/cool cycles and allow corrosion to start - starting the cascade on the way to a melted connector and shutdown or other corrosion effects. In 12V circuits, since current drop isn't really the issue there, the loose/corroded contacts could rectify a local high powered radio station and thus modulate the DC with the audio frequency signal. I'm sure that could cause some interesting system effects...
Granted, those ends will not occur on many modular PSUs, but the potential is there.
Make sure ALL the modular connectors at the PSU end have latched connectors - that will go a long way to helping prevent problems.
Treating your contacts when new with Caig Labs Deoxit Gold or similar will also reduce or eliminate contact-related problems.
But as for myself, I'll stick with hard-wired PSUs, thank you.
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