> -----Original Message----- > From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Robert > Jarratt > Sent: 13 December 2015 15:47 > To: 'General Discussion: On-Topic and Off-Topic Posts' > Subject: RE: VAX 4000-500 PSU Overload? > > > > > I have been able to remove the leaking ones from the +12V and -12V board, I > just have to wait for the new parts to arrive. The two on the 5V and 3.3V > board have not leaked, are not bulging, and are harder to remove without > removing the bottom heatsink or pulling from above as you suggest. I have > not been able to reach them with my ESR meter either, unfortunately. I am > tempted to leave them, although pulling from above is an option. Does > anyone else agree with the pull from above solution? In case you have not > seen it, the design makes it very hard to get at the underside, you have to > desolder a load of transistors to do so, and they are not in easy locations > either. >
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. Thanks Rob