Hi, new to the forum and hoping someone can help out...
I recently bought a ~10 year old 6kVA/4200W APC SMART UPS secondhand online and it appears to be dead-on-arrival. While I may be able to get back what I paid for it from the vendor (wasn't actually that much), with freight costs to return it I'd still be several hundred dollars out of pocket so trying I'd rather try and repair it (or have it repaired locally).
Symptoms: With or without power connected attempting to turn it on results in the green 'online' LED lighting very briefly, then goes out and a red 'Fault' LED comes on. When this happens the battery indicator lights the lower 2 (out of 5) segments. According to the APC documentation this appears to be an 'Inverter Error'.
The battery packs both appear to be fine, and the batteries are reading ~184V combined (about 92V each) which although low seems to be within the APC quoted minimums (nominal is 96V for the 8x12V Lead Acid cells in each of the 2 packs).
The UPS logic board appears to be working fine - when mains is applied the fan in the front of the unit comes on, buttons on the front panel work and the APC network management card works (I can connect to this from a web browser after figuring out the weird APC DHCP option required to give it an IP address on my home network). I don't know the 'apc' user password, but the secondary 'device' login was fortunately still set to the default password and I can use this. The web UI also shows an 'inverter error'.
I opened up the unit to see if I could spot anything that had obviously blown up or overheated, but all appears to be fine visually. Based on another thread
here I tested what I believe is the inverter output capacitor (marked as TMPP 206K/400V) (it's the huge yellow capacitor that had obviously self-destructed in the other thread and was 10uF - but that was for a 1kVA model and not the 6kVA one I have). Anyway, the in-circuit capacitance from my trusty EEVblog 121GW meter is showing this capacitor as only 0.25uF.
So a few questions:
- Is this capacitor meant to be 20uF? I can't find any schematics for this model of UPS and although I have managed to google the service manual, it doesn't include part values. The '206' on the markings suggests 20uF to me(?)
- Should I try and desolder the capacitor and check it again out-of-circuit or just assume it's bad and replace it? It's going to be a bit of a mission to get the main board out of the unit but guess I'm going to have to do that anyway for any sort of repair/replacement.
- Is something like this this a suitable replacement part?
- Any other suggestions to get this up and running? I'm in Christchurch NZ and shipping this thing around is not very practical due to the size & weight, but if there's anyone local experienced with this type of repair I'd be keen to find them.
Would really like to get this working if at all possible, thanks in advance for any assistance!