Robert Jarratt wrote: > > Tonight I replaced the leaking capacitors on the +12V/-12V board, and also > > replaced the two similar ones that looked and measured fine. I put the PSU > > back together, put in a couple of less important boards and drives, and > the > > machine now seems to power on OK. I measured the ripple using the power > > connector for the front panel and that looks OK too. Unfortunately though, > > that connector only sends out +12V, +5V and -12V. It does not have output > > for +3.3V, so I have not, so far, been able to check the ripple for this. > It is a bit > > awkward to test on the bench with a dummy load. > > > > As I did not replace the capacitors on the +5V/3.3V board, because the > > underside is very hard to access, and I am reluctant to pull them off and > > solder from above, I would like to be sure there is no ripple on the 3.3V > > supply. So, I was wondering if anyone has any neat tricks for probing the > > +3.3V supply with the PSU installed in the machine? > > > > Next job is to replace the capacitors on the little DSSI terminator, they > are > > easy to change. > > > > > I spoke too soon :-( > > The machine stayed on for a couple of minutes and then powered off. I > suspect there is a problem with it detecting an overload that may not > actually be there. Looks like I will need to get a dummy load and put it on > the bench to see if it still happens there. > > I do recall that when it first failed it would stay on for shorter and > shorter periods each time I tried it. So perhaps there is some component > warming up and then causing a failure? > > Regards > > Rob
...sounds very similar to my experience with that PSU. The cure seems to be simple run that machine then mine has stopped powering off now it seems. I don't even know if the power off is because of an detected overload at all, I had problems to even power on the machine the first time before changing the caps. It would start only the approx 5 time if I switched it on and I think that those problems are related. I've installed VMS 7.3 and some additional packages and played for some days with that machine and it is running stable now if I power it on. The only thing that I still have to complain about is that the NiCad Pack is empty again a little to fast for my taste, the Battery was a new one.. Regards, Holm -- Technik Service u. Handel Tiffe, www.tsht.de, Holm Tiffe, Freiberger Straße 42, 09600 Oberschöna, USt-Id: DE253710583 www.tsht.de, i...@tsht.de, Fax +49 3731 74200, Mobil: 0172 8790 741