> -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Paul > Koning > Sent: 20 December 2015 22:32 > To: General Discussion: On-Topic and Off-Topic Posts > Subject: Re: VAX 4000-500 PSU Overload? > > > > On Dec 19, 2015, at 4:05 PM, Robert Jarratt <robert.jarr...@ntlworld.com> > wrote: > > > > ... > > I can't tell if this is a Kelvin connected one or not, although I > > suspect it probably is. You can see a picture with two here: > http://1drv.ms/1micVN7. > > These are from a second board in the PSU, but they look identical to > > the one on the problem board. It would appear to have 4 connections, > > but doesn't look anything like the only Kelvin connected one I could find. > > It does look like a Kelvin hookup. Yes, usually they are two fat and two > skinny connections, but so long as two connections carry the current while > the other two do not, it's valid. >
Thanks Paul, I have been assuming that it is Kelvin connected for the time being. I have no idea if the resistor is faulty or if the fault is in the detection logic. I am not entirely sure how to test it, and if it is faulty then finding a replacement may be hard. If it is the detection logic, then I am really in trouble because it is all SMD stuff, the board it is on appears to have multiple layers and I can barely make out the markings on the components, so I can't identify their type (resistor or capacitor) or value, and I have never desoldered/resoldered SMD before. There is an op amp and a comparator, which are easily identifiable, but there also appear to be some transistors, and although I can see the markings "A4H" I have been unable to identify what type they are, what the pinout is or if they are even transistors at all (but I think they must be). Pictures of the logic board here: http://1drv.ms/1QT7641. I also noticed another very low value resistor, 0.01R, which looks far more conventional (not kelvin connected for sure, it looks just like any ordinary resistor, only a bit chunkier), but sadly, it seems to measure fine using my ESR/Low Ohms meter, when measured in circuit. Regards Rob
