On 10/9/2015 10:42 PM, Josh Dersch wrote: > > Capacitor C4 looks to be involved with the START-UP DRIVE signal > circuitry (which drives the relay) so the behavior I'm seeing makes > sense if C4 died and took a couple of things with it (or if something > else died and took C4 with it). > > Here's where it gets kind of odd -- I spent some time testing diodes and > transistors in the related area near C4 and while doing so I noticed > that there are four diodes (D1-D4) listed on the schematic that are > missing from my board. "Missing" as in someone clipped them out at some > point -- there are just nubs of the leads left. I'm not sure why this > would have been done, but there were a number of ECOs applied to this > board (a few wires and resistors added) and I don't want to assume that > if I just put four new diodes in that it won't cause other problems. > Anyone know if there were other revision levels of the bias/interface > board that would have done away with these diodes? Anyone have an H7140 > they can easily crack open to compare? (It's actually relatively easy > to get to, if you can get to the supply...) > > Thanks as always, > Josh >
I have an HP drive (RK05 type packs) whose startup power supply had been tampered with in very odd ways - missing parts, etc. (and maybe even blown out circuit board traces - I forget - I haven't worked on that drive in years). I seem to recall that it looked like it had failed catastrophically at some point. I ended up wiring in a 24V stand alone supply temporarily as a startup supply and got the rest of the supply going that way. Maybe someone did something similar with your supply, and then ran out of time / gave up. Perhaps they clipped the diodes out to test them. I have an 11/40 and an 11/45, so I probably have an H7140 (but I don't seem to have a spare anywhere, which surprises me a little, because I got parts of another 11/40 at one point), but I recall that the things are nightmare-ishly heavy to mount, and there is only one of me, so unless the area in question is visible without taking the supply out of the rack, I doubt that I can help very quickly. JRJ