Electronics > Repair

APC Smart UPS 6000 Repair [FIXED]

(1/3) > >>

Jaxey:
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!

elecdonia:
Catastrophic visible failure doesn’t always take place. The capacitor may look fine externally. Measurement of uF is the standard way to test these large metallized-film capacitors.

It isn’t possible to measure uF accurately with the capacitor “in-circuit.” Unsolder one end of the large yellow inverter capacitor and then test it for proper uF. Make sure capacitor is discharged before connecting meter.

This type of capacitor, known as “metallized film,” tends to gradually lose uF as it ages. A loss of more than 10% indicates it should be replaced. Example: A 20uF capacitor should measure >18uF.

bdunham7:

--- Quote from: Jaxey on June 10, 2023, 12:52:38 pm ---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.
--- End quote ---

Yes, based on other similar products I've worked on and the '206K' markings it is likely 20uF, with that value not being very critical--it would likely operate with 15, 20, 22 or 27uF.  It probably also operates a bit noisily with even lower values.  This is a metallized PP capacitor that is 'self-healing', meaning if there is a dielectric failure it internally discharges a bit of energy that melts it in a way that heals the failure at the cost of losing that area's capacitance--sort of like a scar.  If that happens enough, the value of the capacitor drops.  In 230V-land, this capacitor is very marginally specified and it is very possible that this is what has happened.

Yes, you should absolutely remove the board and capacitor and test it both for capacitance and leakage (ohms).  If you find it to be bad as you suspect, you likely have found both the problem and the solution.

Yes, the general type of part you show is appropriate.  It seems to be very difficult to find exact replacements for these and the large low-voltage capacitor found in the 24V inverters, the biggest problem being that most good replacements are physically larger.  I think APC got them specially made at low-ish cost and while they do typically work for quite a while, they seem to be just the bare minimum for the job.  You can't use just any capacitor here, it has to be very low dissipation and metallized PP is one of the few types that can meet the specs and not be excessively large.  If you have room to put in a larger unit with a higher voltage rating, that might be a good idea.  Perhaps look for welder inverter capacitors.

https://www.aliexpress.us/item/3256803884287671.html

My only other thought is that you need to be very careful with this unit.  It's pretty easy to blow them up or even hurt yourself with that high battery voltage.

Jaxey:
Thanks both for the responses, looks like next step is to remove the main power board and desolder at least one end of the cap and check it again out of circuit.

And @bdunham7 appreciate the warning, I'm only a hobbyist but well aware of the risks around these types of boards and have already checked & discharged all the large caps on the board (and obviously being very careful around these until proven discharged). Luckily on these models it's very easy to disconnect the mains & batteries and make sure the 192V from them and the +/-400V from the inverter isn't present.

There probably is some room for a physically larger capacitor like the one you linked (but would have to run appropriate leads to the board from it), will consider that if/when the existing one is confirmed dead.

bdunham7:

--- Quote from: Jaxey on June 10, 2023, 07:43:31 pm ---There probably is some room for a physically larger capacitor like the one you linked (but would have to run appropriate leads to the board from it)

--- End quote ---

Is there something in the way just above the board?  It would be best if you kept the lead length to a minimum.

Also, what is the exact APC model number of this unit?

Navigation

[0] Message Index

[#] Next page