On Wed, 2 Nov 2022, Peter Coghlan via cctalk wrote: > > Did you have to replace the power LED at all? I've just bench-tested the PSU > > I've swapped the X2 cap in (luckily it powers up without a load, so all I > > did was hook up a DVM and check out the voltages), and I noticed that the > > LED didn't light. I'm pretty sure I connected it back (and it is keyed!) so > > I think I may be looking for a replacement. Something in the back of my mind > > says that there is something that makes the replacement slightly non-trivial > > (funny LED, odd housing it fits in, some trick to getting it out ... I can't > > remember unfortunately). > > > > The LED is more than just a power on indicator. When it fails to light, > it can indicate that something is not right in the PSU. It may tie in > with the "power good" output from the PSU.
It does. I have an H7821 PSU where the LED lights briefly upon power-on and then goes dark. The PSU cannot be used to power a mainboard as it does not come up, however it works just fine with storage in an expansion box. It is one of those that I recapped after leaks have appeared; in fact it is the one that made me aware of the problem in the first place. I'll have to get back to it sometime to get this sorted. > It could be that it is failing to light because the regulation is not > working properly because there is no load. I'd try it with a load > before anything else. The H7822 may need a load on both boards. There's a 2Ω dummy load on the 5V line in storage expansion boxes powered by the H7821, so these do require minimum current to work correctly. > > BTW was it just the 1800uF 25V 105degC caps (mine are brown) that you had to > > replace? Mine look fine but there are some other large electrolytics in > > there (two large brown 470uF voltage unclear, and one large black cap by the > > mains input on which I cannot see any of the markings). > > > > It was only the 1800uF 25V capacitors were bad (mine are all brown too). > In an earlier posting I said there were six of them in a H7821 and ten of > them in a H7822. I should have said five in a H7821 and nine in a H7822. > The 470uF 400V capacitors in my units were all fine. Same here, five 1800uF 25V caps to replace in the H7821 according to my notes. Overall if you spot a cap that says SXF on it, then replace it right away whether already leaking or not. These were made by Chemi-con. Other Chemi-con lines reported problematic are SXE and LXF, though from own experience they seem less prone. Also Nichicon PL and PF parts may have to be replaced, I have seen the former ones actually leaking in other DEC PSUs, such as the H7826, which is also infested by SXF parts in various capacitances. Both kinds leaked in a generic industrial Bel Power PSU used with a Cisco device. Sadly the problem with component shortage has hit capacitors as well and some that used to be readily available are not anymore and prices have risen too. NB I wasn't aware about the problem with RIFA capacitors, it seems like I might have to replace them in several PSUs I have already recapped, sigh. I haven't seen any of them fail though, not at least in an obvious way. HTH, Maciej
