dave@murphy.UUCP (Lerxt) (09/12/86)
Summary: Something you can do to improve the reliability of your 9900 Line eater: enabled Hi there. Since there's been a lot of talk about System Industries 9900 controllers here recently, I thought I'd mention a trick that I found which could improve the reliability of your 9900 (and possibly other con- trollers in the 9xxx series). (Note: in performing the following procedure, it helps a lot if your controller is mounted in a rack on rails so you can pull it out, and high enough so you can get underneath it.) The next time you bring down your VAX, go turn off the 9900 and slide it out of the rack. Get underneath it (or turn it face-up if you have those fancy swiveling slides) and take the bottom off of the box. These will expose the controller motherboard, which is a massive, heavy board which covers the entire bottom of the box. There is a metal plate separating this area from the rest of the box, with cutouts for the ZIF connector pins (which interface to the machine and drive interface boards in the top part of the box). Notice how the motherboard is mounted. In the 9900's that we have here (they may have changed this, so yours could be different), the motherboard is bolted to the metal plate at the front end, but the back end *isn't supported at all*. The pins for the ZIF connectors are located about 1/3 of the way back from the front end. This means that these connector pins, in addition to performing their electrical function, are supporting most of the weight of the motherboard. Now, this board is REAL HEAVY, and the unsupported weight of the rear end of the board puts a considerable torque on the connector pins -- enough to crack the board and lift traces off in the area around the pins. The cure for this is to take two small pieces of foam or other soft, non- conducting material (the little foam blocks that they put in new mag tapes work well), and place them at the rear of the box bottom so that they will hold up the back end of the board. Be careful that the foam doesn't touch any unmasked traces. This will take the stress off of the connectors, and your 9900 will thank you for it. A motherboard which is cracked in the area around the connectors will generate all sorts of bizarre symptoms; in one instance, I watched while an SI field engineer tapped on a damaged board in the area around the connectors with a screwdriver handle, and when he hit a certain spot, a CDC 9762 that was connected to the controller *spun down* (and the 9900 isn't even supposed to be able to do that)! If your controller is under warranty or service contract, consult with your field engineer before performing this procedure (I can't imagine that they would give you any argument about it, as long as they think that you know what you're doing). Generally, the 9900 is a pretty reliable gadget, and together with a rack of Eagles, the average access time, $/MB and MTBF is hard to beat. --- It's been said by many a wise philosopher that when you die and your soul goes to its final resting place, it has to make a connection in Atlanta. Dave Cornutt, Gould Computer Systems, Ft. Lauderdale, FL UUCP: ...{sun,pur-ee,brl-bmd}!gould!dcornutt or ...!ucf-cs!novavax!houligan!dcornutt ARPA: wait a minute, I've almost got it... "The opinions expressed herein are not necessarily those of my employer, not necessarily mine, and probably not necessary."