APC UPS - pls help me identify the problem

I am using this old APC-BK500MI ups for my desktop PC short backup only , For couple of days it has stopped giving backup and showing a strange behavior i.e even with switch turned off it doesn't cut the power to attached appliances switch is not digital as you can see it is usual On/Off

The CBS dry battery is almost new and healthy and when power fails UPS does gives usual beep and I think charging is also working because battery never went below 13.4V (i'm checking it through meter)

So before buying a new one i want to know if something i can do myself (with my basic soldering skills) i usually don't go to electricians either solve the problem myself or just throw the thing away
Real Question is : Is this something related to RELAY?

bk500mi.jpg

You should suspect a stuck relay contact. I think your relay is located is located near the black big on board transformer.

[quote=“Ijaz_Ahmed, post:2, topic:22556”]

You should suspect a stuck relay contact. I think your relay is located is located near the black big on board transformer.

[/quote]

So just changing the relay will solve the issue? also how do I know the specs of this relay?

You should first check if it is really a sticky relay?

It may be hard to find this relay but if you are in Lahore, you can check on Hall Road.

that is very strange n unusual behavior of any ups of apc i hv ever heard ...i suggest u instead of wastin' ur time on repairin' thing u shud buy nother used one either old model that u hv or new model of this series ... cux this ups is offline topology .. and also its very cheap compared to other models ......

[quote=“Ijaz_Ahmed, post:4, topic:22556”]

You should first check if it is really a sticky relay?

It may be hard to find this relay but if you are in Lahore, you can check on Hall Road.

[/quote]

I do not know how to identify the sticky thing but I have checked and yes it’s the relay which is culprit everything else is working fine … Because relay is not even producing its sound … i searched the web but couldn’t find its specs it has 8 points how do I go and buy the replacement are there any general type of relays like this? Any suggestions?

[quote=“APC_UPS, post:5, topic:22556”]

that is very strange n unusual behavior of any ups of apc i hv ever heard …i suggest u instead of wastin’ ur time on repairin’ thing u shud buy nother used one either old model that u hv or new model of this series … cux this ups is offline topology … and also its very cheap compared to other models …

[/quote]

this is kind of strange to hear from UPS expert :lol: Yes time is important for me I was already going to buy a new one and to keep this one as backup …

But do you have any idea of relay specs? i need relay specs …

This is double pole double throw DPDT type relay. You may or may not find the exact size (footprint).

If you have soldering / de-soldering experience, you may take put the relay and check it outside if it works or not. I hope it is 12V DPDT type.

There should be a part number on the side of relay. Can you post that number here?

Any relay of comparable specifications can be used. However you may need to mount it using small pieces of wires since the size wouldn't fit on PCB.

[quote=“Ijaz_Ahmed, post:8, topic:22556”]

This is double pole double throw DPDT type relay. You may or may not find the exact size (footprint).

If you have soldering / de-soldering experience, you may take put the relay and check it outside if it works or not. I hope it is 12V DPDT type.

There should be a part number on the side of relay. Can you post that number here?

Any relay of comparable specifications can be used. However you may need to mount it using small pieces of wires since the size wouldn’t fit on PCB.

[/quote]

Many thanks for this very professional tip to check it outside the circuit if it is really the culprit ,I have not taken it out from the circuit yet Will do it in my spare time … for the moment I’m going to buy a new one and will get back to this UPS to prepare it as backup

Thank you again for all the help

If relay failed, you should also find out what caused it to fail (like bad capacitor or bad transistor, etc.) or new relay may also fail. Look for heat damage/darkened or distorted/buldging parts.

[quote=“noman89, post:7, topic:22556”]

this is kind of strange to hear from UPS expert :lol: Yes time is important for me I was already going to buy a new one and to keep this one as backup …

But do you have any idea of relay specs? i need relay specs …

[/quote]

well buddy … i told u this one is very very old model … if i had the ups itself i wud hv given u its board or whole ups as courtesy cux none ov my clients likes offline topology ups … plus if by chance any client gives this ups to us we simply xchange the ups with new model … cux time is money n this ups dont worth repairin cux of non availability of its parts …

[quote=“F11, post:10, topic:22556”]

If relay failed, you should also find out what caused it to fail (like bad capacitor or bad transistor, etc.) or new relay may also fail. Look for heat damage/darkened or distorted/buldging parts.

[/quote]

Dear I purchased it new 10 years Ago :lol: and it worked flawlessly Relay is the main and only moving part in it so it makes sense that it finally said Goodbye cruel world … :lol:

But thanks for your suggestion anyway, I got this idea from @ijaz ahmed when he said check it outside the circuit , And if there is anything else is wrong I will not waste my time with it … and one thing is sure that the replacement Relay is not going to be that high quality …

Noman

Before desoldering the relay see if an equivilant is available which will fit pin to pin.

There are other considerations like placement of normally open and normally closed contacts which maybe differ from the originally installed relay. So this is also something to watch out for.

Finally if you can't find the original or a pin to pin fit, then you can also run wires to a totally different relay to its equivalent pins. The ralay itself can be taped to a convinient location inside the ups and can even lie on top of the pcb after applying adequate insulation and keeping it a safe distance from high voltage or high heat components.

Aurangzeb