Hi Maciej, > > Right, my notes indicate Nichicon PL parts might be problematic too, e.g. > one at 4700uF/10V on 5V output of the H7826 PSU. >
What is H7826 used in? I don't think I have any of those. > > I can confirm now Nichicon PF 47uF/35V parts to be the source of an issue > with my Bel Power. All four leaked. Thankfully I was able to fully > revive that PSU (now in 24/7 operation). > I got replacement capacitors for my POWER-ONE unit but I haven't managed to obtain a replacement IRFPE50 chopper transistor yet. I found a sort-of local supplier that lists them but they have a EUR 30 minimum order and they don't stock much other stuff I need or want :-( > > These are likely standard type parts. I've yet to come across a low > impedance axial capacitor type. I may have missed something of course. > I couldn't find any suitable axial replacements so I ended up using radials which were roughly the same height as the width of the axials. > > > > > > Heat dissipated by the cap itself under high ripple current never helps > > > and will surely speed up cap deterioration. After all its service life > > > halvens with each 10°C temperature rise even with non-faulty parts. > > > > > > > When I was shopping for replacements, I was a bit alarmed to find that > > the maximum specified "endurance" (whatever that is) I could find was > > 5000 hours. This isn't much more than a long life incandescent light bulb. > > Mind that it's at 105°C. If you keep such caps operating at 65°C (which > is still rather hot), then endurance raises to 80000h (~9 years continuous > use). > > Anyway try to chase replacements specified for at least 10000h at 105°C. > Nichicon HE/UHE and Panasonic FR seem suitable replacements for Chemi-con > SXF, Nichicon PL, surpassing old parts in terms of ESR/impedance/ripple > and dimension-wise. > When I was trying to order them, I found it hard to get anything suitable. I ended up ordering 15 (out of 16 in stock at Mouser) Panasonic FC series to do just three PSUs. > > I don't have any H7822 PSU. Your experience with the H7821 is the same > as mine though (and I still need to figure out what's wrong with one which > still doesn't drive its power-good line active after recapping). > There is a 464 or 560 Ohm resistor near the capacitor in middle of the H7821 which has been damaged by leakage in several of my PSUs. It is in series with a thermistor mounted on a heatsink and as far as I recall it is part of the fan control circuit. It might also contribute to power-good though. Other components could be damaged too or there could be goo lying under some components. > > I used > Nichicon HE P/N UHE1E182MHD as the replacement for those. There does > appear to be COVID-related shortage of this part (600 expected at Mouser > 15/03/2023, ugh!), which used to be readily available in large quantities > several years ago. However Panasonic FR P/N EEUFR1E182 is available in a > small quantity (and is better). I should grab some EEUFR1E182 before they disappear. > > I came across LXF parts in one H7826 only and they were clean, but I > chose to replace them as a precaution anyway as I've got stuck with trying > to repair a couple of broken H7826 PSUs already still not working after > cleaning the mess and replacing broken caps (mind that I'm a software > engineer with enough hassle to sort out on the software side already). > Sounds like it was better to not take a chance on them. > > I've seen leaks from SXF parts on the primary side too with the H7826, so > it is not that they only fail on the secondary side. Also it is lower > frequency ripple that's more problematic, see frequency correction factors > for ripple current in datasheets, because impedance is higher at lower > frequencies. That's an inherent property of capacitance. > That makes sense. > > > I replaced the five leaking capacitors on the upper board in my H7822, > > disconnected the input to the lower board and moved the LED connection to > > the upper board. The machine powered up nicely afterwards, the fans spun > > and the green LED came on after a short delay. However, the diagnostic > > LEDs all come on and stay on so it appears the CPU is being made aware that > > the lower board is not functioning, even though I don't need it. I should > > to do some comparisons with a H7821 and see if I can work around this. Or > > maybe I could fit some not quite to specification electrolytics from the > > junk box on the lower board, just to keep it happy? > > The symptom is exactly like with my broken H7821. Check the power-good > signal (brown wire with the H7821, possibly likewise with the H7822). It > should be driven high at the TTL level. > The wire in the same position as the brown one on a H7821 is purple on a H7822 and they both seem to have the same function. I ended up temporarily fitting a two 1000uF/25V capacitors on the lower board of my H7822 and reconnecting it to the upper board. This gave me +5.1V on the purple wire and the CPU then ran ok for test purposes. I have a VAX 4000/100A which has a Zytec Model EP 071181 power supply. The only Digital reference on it is 30-35042-01. It is the same physical form factor as the H7822. The output connectors look the same, including the wire colours except +12V is brown instead of orange and this one has an extra connector for 3.3V (which is not used for anything in the 4000/100A). The reason I mention it is there is a list of output voltages on the label: +5.1V, +12.1V, +3.3V, -12V and -9V. By a process of elimination, the -9V supply must be the grey wire (which gives me -8.2V when I put the meter on it. All the other voltages are much closer to specification). I wonder if the grey wire in the same position on the H7822 is also supposed to be -9V? When I try to measure it on my H7822, I get a negative voltage but it is wandering around -4V. In contrast, the -12V supply on the blue wire is a steady -11.99V, probably due to the 7912 regulator. The same wire as the grey on the H7822 is yellow on a H7821. I measured the voltage on a working H7821 and found a steady -0.2V which seems odd. Do you know what the white wire is for? I originally thought it might be power-good but only because the white wire on a H7816 seems to be power-good. On the 30-35042-01, it is slightly above 0V. On my H7822 it is about 5.6V and on my H7821 it is 8.8V. Regards, Peter. > > Maciej
