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APC Back-UPS 650MI PCB Fault

andrewclark

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Hi
I noticed some other posts on here about APC UPS and it seems that some posters have good knowledge of this kit.
I was extending my (working) UPS to use a larger external 12v battery with long cables and had put it back together again with the battery in. I had turned it upside down to solder the last croccy clip on using my Helping Hands stand when I accidentally shorted the + terminal to the metal case through the stand I was using. :)cry: Doh!).
Checking the PCB I found an open circuit 5A Fuse 4 on the board clearly blown. I soldered in a new fuse wire thinking that would sort it but the unit still won't fire up when offline although it charges the battery OK.
Fuses 1, 2 and 5 test out OK and I can't see a Fuse 3 anywhere!
The board carries the number 640-0214E Rev 05.
Without a circuit diagram I am struggling to diagnose the second fault. Can anyone give a steer what to check please or find a circuit diagram for the unit?

Any help appreciated
Thanks in advance
Andrew
 

BradtheRad

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unit still won't fire up when offline although it charges the battery OK
Is it designed to provide AC power as a standalone unit? An old UPS I worked on only provided power either: (a) when it lost its existing connection to mains AC, or...

(b) when I pressed a relay inside the enclosure so it closed.

In other words it did not operate as a standalone unit.

Did your UPS previously work as a standalone unit?
Or else can you locate a similar relay inside?
 

andrewclark

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Is it designed to provide AC power as a standalone unit? An old UPS I worked on only provided power either:
(a) when it lost its existing connection to mains AC, or...
Thanks for getting back to me.
It worked even without the mains cord plugged in, beeping to let you know that the power was off. It doesn't do that now and you can't even hear it kicking in.

(b) when I pressed a relay inside the enclosure so it closed.

In other words it did not operate as a standalone unit.

Did your UPS previously work as a standalone unit?
Or else can you locate a similar relay inside?
Yes, it worked as a standalone unit.
Yes, it has a relay in the circuit. I can energize that with 12v when disconnected from the battery and the relay clicks OK but I would need to be careful trying it live as the circuit is designed to output 230V AC (UK Mains voltage)!
 

andrewclark

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Another question: Does the inverter need to have a load attached in order to turn on?
Or does it stay off if it senses no load?
I'm pretty sure it doesn't need a load attached. Normally you can hear the transformer buzzing loudly on these when they are operating on battery (I have used APC for years), and, as I said, it was operating on battery before I started the project just beeping to alert me that it was not plugged into mains.

It may be that I have damaged something in the mains sensing part of the circuit as even if I close the relay with a 12v dry battery it still does not start operating. However there are literally dozens of small transistors in the circuit as well as ICs any of which could have been damaged. A bit surprising though that the 5A fuse didn't protect the circuit since it did blow. But perhaps the designer did not envisage some idiot shorting the 12V live to the mains Earth! :???:
 

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The accidental reverse polarity must have damaged devices before the fuse blew. This might include body diodes inside mosfets if they're used.
Or electrolytic capacitors. Etc.

There could be a controller somewhere detecting something isn't right, therefore the unit doesn't turn on. Does it flash a code, or beep a certain number of times?
 

andrewclark

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The accidental reverse polarity must have damaged devices before the fuse blew. This might include body diodes inside mosfets if they're used.
Or electrolytic capacitors. Etc.

There could be a controller somewhere detecting something isn't right, therefore the unit doesn't turn on. Does it flash a code, or beep a certain number of times?
There is no display. No beeps, only a faint click from an unidentified component somewhere as it is powered up on battery.

I need to get a circuit diagram for the board. I have found one for a slightly different, probably earlier model but still looking...
 

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I can't see a Fuse 3 anywhere!
Finding it is probably key to fixing the unit. Although labels often say 'No user serviceable parts inside', fuses really are there for someone to service.

My personal stories:

I once hooked up my 800W power inverter to a battery in reverse polarity. My mistake blew more than one fuse. Blade type as used in automobiles. I had to test all of them. Replacing the bad ones finally made the unit work. I was lucky that the fuses were easy to locate.

My 2500W power inverter stopped working after I allowed it to make a freak connection through a metal table, to a copper pipe carrying fuel oil, to house wiring somewhere. I had to replace one of the MOV's inside before it would work. It looked like a large blue ceramic capacitor.

Fuse #3 might be glass tube type, or solid cylinder, or fusible wire, or blade type, or circuit breaker.

There are also thermal fuses which open up at high temperature. I replaced one among coils of wire in a fan. It resembled a silver-colored resistor.

Such fuses might be labelled with abbreviations instead of 'fuse' or 10A or 20A. Such as CB or FW or FL or TF, etc.

Circuit breakers reset via push button.

A fusible link might have insulation with a spiral color pattern, which may or may not reveal that it's blown. A good one should show low resistance with an ohmmeter.
 

andrewclark

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Finding it is probably key to fixing the unit. Although labels often say 'No user serviceable parts inside', fuses really are there for someone to service.

My personal stories:

I once hooked up my 800W power inverter to a battery in reverse polarity. My mistake blew more than one fuse. Blade type as used in automobiles. I had to test all of them. Replacing the bad ones finally made the unit work. I was lucky that the fuses were easy to locate.

My 2500W power inverter stopped working after I allowed it to make a freak connection through a metal table, to a copper pipe carrying fuel oil, to house wiring somewhere. I had to replace one of the MOV's inside before it would work. It looked like a large blue ceramic capacitor.

Fuse #3 might be glass tube type, or solid cylinder, or fusible wire, or blade type, or circuit breaker.

There are also thermal fuses which open up at high temperature. I replaced one among coils of wire in a fan. It resembled a silver-colored resistor.

Such fuses might be labelled with abbreviations instead of 'fuse' or 10A or 20A. Such as CB or FW or FL or TF, etc.

Circuit breakers reset via push button.

A fusible link might have insulation with a spiral color pattern, which may or may not reveal that it's blown. A good one should show low resistance with an ohmmeter.
Brad
Those suggestions are very helpful. I found F3 at last and, as you suggested, it didn't look like a fuse at all being in a stubby little cylindrical package adjacent to the small transformer. However it does not appear to be blown as it reads 1.9 ohms both ways.
There are also a couple of MOSFETs, labelled MOV1 and MOV2 (I was wondering what sort of device that was). I don't know how to go about testing one of those. MOV1 exhibits very high resistance in both directions on my meter. MOV2 is 4.2 ohms both ways, both tested in-circuit. I could maybe de-solder those if I have to though I am struggling to get the pcb out due to the large number of heavy-gauge cables connected with spade terminals - I will have to pull them all off to get it out and have taken several photos of them in case I am reduced to doing that!
There is also a thermal breaker with a reset button on the mains output but that checks out OK and is nc.
Happy to get any suggestions as to what to try from here...
 

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MOV2 is 4.2 ohms both ways, both tested in-circuit. I could maybe de-solder those if I have to though I am struggling to get the pcb out
MOV= metal-oxide varistor. Common form of circuit protection. It's designed to have high resistance in normal operation. It conducts when exposed to overmuch voltage.

So your MOV2 sounds like it's blown.

Ordinarily it survives many brief voltage spikes that come through house voltage every so often. But one severe jolt destroys it.

I chose a replacement from a catalog listing. I had to look over part designations containing a lot of characters. AC voltage is there (120 or 130V in USA). I think also power rating, or speed rating, or joule rating. Maybe size too. I wasn't certain I chose the right one and I was just happy it made my inverter work again.

- - - Updated - - -

Is it easier for you to clip one of its leads? Your unit may then work with it gone, since an MOV is not supposed to conduct normally.
Possibly then solder a replacement to the other side of the board, if that's more accessible?
 

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MOV= metal-oxide varistor. Common form of circuit protection. It's designed to have high resistance in normal operation. It conducts when exposed to overmuch voltage.

So your MOV2 sounds like it's blown.

Ordinarily it survives many brief voltage spikes that come through house voltage every so often. But one severe jolt destroys it.

I chose a replacement from a catalog listing. I had to look over part designations containing a lot of characters. AC voltage is there (120 or 130V in USA). I think also power rating, or speed rating, or joule rating. Maybe size too. I wasn't certain I chose the right one and I was just happy it made my inverter work again.

- - - Updated - - -

Is it easier for you to clip one of its leads? Your unit may then work with it gone, since an MOV is not supposed to conduct normally.
Possibly then solder a replacement to the other side of the board, if that's more accessible?
Hi Brad
Well I de-soldered MOV2 and found that it actually has high resistance when out of circuit so I soldered it back in again.
However the good news is that the unit is actually working now but it doesn't sound the buzzer when working offline - that was what was making the clicking noise so I guess something in the buzzer circuit is blown, or the buzzer itself. However I can live without that noise! I'm going to put it back together (more carefully this time :-D ) and put it back in place in the garage and see how it goes. In case you wonder why I'm using it there the garage has an electric door, but the RCCD for the house mains is in there so if it trips I cannot otherwise get in to reset it!
So I'll thank you greatly for your helpful advice and keep my fingers crossed that it will work now.
:-D:-D:-D
 

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Now that's certainly cause for congratulations!

Often we fix something without knowing just how we did it.

Do you by any chance have an attic so you could climb up from the living area and climb down into the garage?
 

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Now that's certainly cause for congratulations!

Often we fix something without knowing just how we did it.

Do you by any chance have an attic so you could climb up from the living area and climb down into the garage?
Indeed. We must actually be cleverer than we think - or more stupid in breaking it in the first place :-?!

Unfortunately there is no other way into our garage apart from the car door - but the replaced UPS is working fine. I by-passed the piezo-electric beeper thingy which had blown by putting a standard buzzer in and that works well.

Again many thanks for your input.
 

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