Hi Maciej, > > > > > What is H7826 used in? I don't think I have any of those. > > DECstation 5000/1xx systems and TURBOchannel Extender boxes. Not sure if > anything else. >
Ok. I have VAXStation/MicroVAX and Alpha systems but no DECStations so that explains why I haven't seen them. > > > Do you know what the white wire is for? I originally thought it might > > be power-good but only because the white wire on a H7816 seems to be > > power-good. On the 30-35042-01, it is slightly above 0V. On my H7822 > > it is about 5.6V and on my H7821 it is 8.8V. > > In the H7821 it's -9Vdc return pairing with -9Vdc supplied on the yellow > wire (an isolated circuit). Pin numbers 14 & 13. Try measuring voltage > across the suspicious connections as any reference to ground may not be > indicative. > Aha - that explains the odd and slowly varying different voltages I've found on these leads in different machines. It didn't dawn on me that they could be isolated from ground. I should have noticed that there were two adjacent leads which behaved like this. This should help clarify some of the puzzles I came across when I was trying to trace the circuit of the H7821 and H7822. Regards, Peter. > > This voltage is also present with the H7819 PSU. It's not clear to me > what it is used for. > > Maciej
