On Thu, Dec 10, 2015 at 11:42 PM, Holm Tiffe <h...@freibergnet.de> wrote: > > Another thing is that small PCB on the DSSI storage Backplane, the Caps > there where dead too. I thing it is the termination Power regulator and in > my case the bad caps "simulated" a bad disk, I could'nt initialize this > disk properly before I've changed the Caps there too.. >
I took a look at the DSSI & SCSI termination power supply board in my VAX 4000 BA440 chassis. It's the small board in the storage area of the backplane mounted in place by a single screw. There are two identical circuits based on the LT-1086 with the adjustable output voltage set at 5.30V [1.25V * (1 + 392/121)]. Each circuit has a 100uF 35V 105C nichicon cap between the input and ground and the output and ground. Both circuits on my board still output 5.3V from a 12V input, but I think the caps are starting to leak electrolyte on the PCB and I should replace them all (4 total) before things get ugly. Each circuit has three diodes, an SB520 and a 1N4735A for which I can find datasheets, and a third one which looks like a General Instrument MP654 for which I can't find a datasheet and I'm not sure if that is the correct part number. I can't quite read the marking all the way around the body of the diode. If someone else takes a look at their BA440 DSSI & SCSI termination power supply board let me know if you can make out what that part number is, or if MP654 is a GI part for which you can find a datasheet. -Glen
