On Tuesday, February 10, 2015 01:49:53 AM Dave Cole wrote: > Yep, I think they are diodes... > > And your diodes don't look very good. It looks like they may have > overheated. > > There are several of those diodes on the other side of the board. > Under the electrolytics and between some of the larger chips near the > power fets. > They all have the same designation on them on my drive.
And I'll bet a cold one they are all Schottky diodes due to 2 things, 1 being the extremely low forward voltage drop, and 2 being their innate nanosecond or better speeds. From the description of where they are, its likely they were the snubbers that are now bult into modern FET's used in H-bridge drivers An open failure will probably damage the power FET's too. > I'd take some of them off and see what you have when you put an ohm > meter across them. If your meter has a diode test setting so much the > better. The diode checker of the modern meter reads the voltage drop, fwd direction on this type of diode s/b under .15 volts, while the reverse of the probes should show a much higher voltage, maybe even off-scale for reverse. Right where they sit in circuit. A reading in both directions that is similar and probably under .1 volts is a shorted one. > If you are going to attempt a repair I'd replace the electrolytics even > if they are not bulged. They are cheap and they fail from age. I concur on that. > Dave > > On 2/9/2015 11:43 PM, Dean Posekany wrote: > > After the comments/recommendations to think about attempting a repair > > to the Parker drives, I popped several open and took a good look > > around. On the top surface I could find no obvious problems. Not > > popped caps, no burn marks, nothing. On the bottom, I found what > > looks to be a problem on two of the bad drives. There are three > > SMD's located near the drive output port that appear to be toast. > > The problem is I can't identify them. The board stencil “CR” > > notation seems to indicate they are crystal rectifiers and you can > > see polarity marks on one side. I tried to track down the SMD codes > > online but had no success. Soooooooo, since some of you spurred me > > on, I thought I'd throw this back out here to see if any of you guys > > had any ideas. I've attached links to three photos that may be of > > some help. > > > > This is a close-up of one of my good drives: > > > > _https://www.dropbox.com/sc/fzugl3ebp7hlbbj/AABZSMn6f70FORZS3FpRhRc-a > > _ > > > > This is a close-up showing the suspect SMD's on a bad drive: > > > > _https://www.dropbox.com/sc/eeoy5dpw1861j54/AAAigtSkz9aLiKBbZVY9FFUia > > _ > > > > And this is a close-up of the shot Dave supplied yesterday for one of > > his Parker drives: > > > > _https://www.dropbox.com/sc/hwfjcjmtqpwjfyh/AAD09FOOfweAwIAbjbs9FRwQa > > _ > > > > It's interesting to note that the SMD part codes on Dave's board are > > different than mine. But I couldn't track down the parts using his > > codes either. > > > > > > Any thoughts? > > > > --------------------------------------------------------------------- > > --------- Dive into the World of Parallel Programming. The Go > > Parallel Website, sponsored by Intel and developed in partnership > > with Slashdot Media, is your hub for all things parallel software > > development, from weekly thought leadership blogs to news, videos, > > case studies, tutorials and more. Take a look and join the > > conversation now. http://goparallel.sourceforge.net/ > > _______________________________________________ > > Emc-users mailing list > > [email protected] > > https://lists.sourceforge.net/lists/listinfo/emc-users > > --- > This email has been checked for viruses by Avast antivirus software. > http://www.avast.com > > > ----------------------------------------------------------------------- > ------- Dive into the World of Parallel Programming. The Go Parallel > Website, sponsored by Intel and developed in partnership with Slashdot > Media, is your hub for all things parallel software development, from > weekly thought leadership blogs to news, videos, case studies, > tutorials and more. Take a look and join the conversation now. > http://goparallel.sourceforge.net/ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ Dive into the World of Parallel Programming. The Go Parallel Website, sponsored by Intel and developed in partnership with Slashdot Media, is your hub for all things parallel software development, from weekly thought leadership blogs to news, videos, case studies, tutorials and more. Take a look and join the conversation now. http://goparallel.sourceforge.net/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
