Repair Instructions for APC Back-UPS RS 500 - Heime

Heime Heime > Posts > Repair instructions for APC Back-UPS RS 500 27.12.2006

Repair instructions for APC Back-UPS RS 500 I have two of these units with the same fault and I have also read about this problem on usenet. The problem is that the Back-UPS RS 500 stop charging the battery. For me it was easy and not expensive to repair them. If you have some experience with soldering it should be easy for you too to do the repair work. Before you start, remove mains power and the battery. This unit is generating high voltage from a 12 volts battery and a battery like this contain a lot of energy. Please take notice of any safety precautions.

Here is the front panel with model name. I suppose yours are similar.

Remove the two screws on the back panel

Lift the panel out at the bottom. It snaps in position at the top and you maybe have to use some force to take it off completely.

Lift out the side panel and disconnect the red and black battery wire. Make sure you know where to reconnect those wires when assembling the unit.

Take a sheet of paper and make a drawing of the circuit board and all the wires to the transformer and back panel. Disconnect all the wires and remove both the transformer and back panel.

Remove the circuit board on the front panel.

Remove the main board. It is fastened with two clips on the back side.

Main board with the faulty capacitor.

C harging unit and the faulty capacitor.

Make sure you take notice of the polarity of this capacitor.

Replace the capacitor with a new one with similar or better specification. I bought mine from here: Elfa

After the unit is assembled, connect it to the mains and measure the voltage at the battery terminals without a battery connected. It should be approx. 13.6 Volts.

Disconnect from the mains and mount and connect the battery. You probably have to buy a new battery if the old one has been completely discharged and been like that for several weeks. Batteries are easily damaged if discharged over a long time. C onnect it to the mains and measure that it is charging the battery. The voltage should be rising slowly up to 13.6 Volts. Posted at 18:36 by Stig Vidar Hovland | C ategory: General | Permalink | Email this Post | C omments (71)

Comments It works!

Thank you for this very detailed fixit. My RS500 failed a few days ago with this problem and replacing the capacitor (with a 33uF 35v component) does seem to have fixed it. I'm watching the battery charge back up again as I type this. I wonder what causes this capacitor to fail? According to my meter it is open circuit and exhibits no capacitance at all and that is a very unusual failure mode! Anyway, thank you again for a very timely posting - you've saved me from spending some money on a new unit. The power of the Internet!

John L (G3WGV), England. at 30.12.2006 11:27

Fabulous¡¡¡¡ Thanks, fabulous tip, I above thank for you and the people like You Ricardo at 09.01.2007 16:27

Just as you wrote It worked like a charm i replaced it with a 22uF x 25V 85°C C apacitor it works!! Now i have to check if the battery is dead... Thank you a lot at 25.01.2007 03:42

thanks thanks, my RS 500 again live. Mirob, Slovakia at 05.02.2007 21:42

Thanks!! Same problem here!!! Thanks for the tip, I'll fetch the soldering iron ASAP 8-) at 28.04.2007 20:29

Thanks so much APC said my battery had died, but I tried this and my UPS is as good as new! Unusual that this is happening on a large number of devices, and disappointing that APC gave me the wrong "solution" when I even linked them to this page to see if they would admit the capacitor was at fault. However, as an electrical engineering student, this was very fun too! Thanks so much for your advice. at 11.05.2007 17:19

GONZALO muy buena solucion hace meses que buscaba la solucion. Gracias ( thanks you) at 12.06.2007 17:09

APC USED WRONG CAP Replace with a 105c cap not a 85c that was in it. A 85c cap works good with 60hz, A switching power supply has a much higher freq and a 85c cap with over heat and develop high ESR, due to drying out. C larence Southwest Monitors & Printers POS [email protected] at 27.08.2007 01:14

THX U SO MUCH I LEAVE IN INDONESIA, I HAVE SOME TROUBLE WITH MY RS500, NOW WITH YOUR BLOG, MY RS500 WA C OME BAC K AGAIN.... I REPLAC E WITH SAME C APASITOR 22uf 16v 85c. MAY BE, I WANT TO RE-REPLAC E WITH 105c C APAC ITOR FOR LONG LIFE C OMPONENT. THX FOR U ALL. at 21.09.2007 22:54

PERMIT FOR RE-VIEW IN INDONESIAN LANGUAGE I WANT TO RE-VIEW OR TRANSLATE TO INDONESIAN LANGUAGE WITH C OMPLATE U'R PHOTO IN MY BLOG, I WILL PUT YOUR LINK, FOR ORIGINALITY SOURC E. THX U.

SVH: That is OK. It would be fine if you give me a link to your translation. at 21.09.2007 22:57

Thanks C ured mine fine, I think I may replace the other caps as several are reading a bit high with my ESR meter, the faulty one would not give any reading. now all I need is some non corrosive silicone to dampen the buzz from the inductors. Ben. NB I used a 105c 35V 22UF low esr capacitor. Thanks for saving me the time of finding the fault. at 25.10.2007 16:19

Mi agradecimiento a esta solucion !!!!!!!!! Desde Buenos Aires Argentina, agradezco sinceramente de corazon, la solucion brindada por este tutorial.Ya daba por perdida mi confiable APC RS 500, cuando descubri esta solucion, por la decima parte de un dolar , volvio a tener vida la tan valiosa ups.- Recomendare este link en los foros de electronica sin duda.Gracias a su autor.Thanks !!!!!!!! at 04.03.2008 22:42

Mi agradecimiento a esta solucion !!!!!!!!! Desde Buenos Aires Argentina, agradezco sinceramente de corazon, la solucion brindada por este tutorial.Ya daba por perdida mi confiable APC RS 500, cuando descubri esta solucion, por la decima parte de un dolar , volvio a tener vida la tan valiosa ups.- Recomendare este link en los foros de electronica sin duda.Gracias a su autor.Thanks !!!!!!!! at 04.03.2008 22:43

APC upgraded the cap for the new builds The C 7 had used a 50V 22uF 105c with unknown manufacturer. Other caps are gold color Jamicon.

Other caps are gold color Jamicon. at 07.03.2008 08:40

EXCELENTE!! Muchas gracias Este tutorial es excelente, le cambié a 4 UPSs el condensador y están cargando perfectamente. Gracias de nuevo. at 17.03.2008 16:00

UPS APC BR 1500 Hello My name is Willan C an you help me? I have have a UPS APC BR1500, and in this moment it is on OVERLOAD state, I repleced the batt and it dont operate, so I see all the electronical elements and I did not found nothing Please, if you have any idea you can help me? PD I am sorry my english is very very bad I from Ecuador at 19.03.2008 21:51

works ! Hi folks, it worked for my APC . It was 1 year broken and now it is charging a new battery. Thanks U and the web. Sleyo at 29.03.2008 16:07

RS 500 Alive again!! Excellent fix!! I was just about to buy a replacement UPS. Many thanks. Neville

UK

at 03.05.2008 19:37

APC Backup 500UPS Do you have anything on fixing power relay? My unit charges the battery but when unpluged from external power it fails to transfer load to battery supply. Harry at 11.05.2008 21:27

APC BE500-AS

Using another apc product. Everything is fine except circuit not charging the battery. How to identify the batery charging capacitor? How do you check faulty capacitors? at 25.07.2008 16:33

Excellent job Indeed works. Thanks

at 26.07.2008 18:21

Anyone seen an overheating problem? C ongratulations on the capacitor replacement instructions -- but I have a different problem with my RS500 (BR500I, 240 V version). It's a new unit, and as soon as I plugged it in it started to give off a scorching smell that has not gone away after 24 hours. The hot spot seems to be near the top vent, on the left-hand side as you look at the front of the unit. This is a replacement for an RS500 that failed with overheating around R28 on the main board -- I suspected the K2608 MOSFET nearby but am not enough of an electronics person to be confident of diagnosing a fault. Does anyone else have experience of overheating with these units? at 21.08.2008 18:15

Working Thanks from Finland friends. at 08.10.2008 23:30

many thanks to u... I have one exactly the same problem and the capacitor replacement indeed fix the problem. regards, john_t Subic Bay, Philippines. at 20.11.2008 09:15

R28 overheat as well BC B was burned around R28 of my APC , even plastic case was bit melted at 09.12.2008 13:37

RS 500 discharging battery

My UPS disarching battery, what problem? at 18.12.2008 19:26

Resisters prob hi in my unit the large resisters have been damaged (burnt out) can you please post or email me there codes or values thanks par_0020 hotmail.com at 05.05.2009 12:22

BackUPS500 Where can I find repair solutions like this for my APC BackUPS 500? It is operational with power coming from the battery but when AC power returns, nothing happens. It operates as if there is no AC power at the input. This is a very good repair guide here. at 02.06.2009 15:56

R28 overheating? Hello, I have same issue with overheating, I have two RS500 with smoked top and PC B, one of them was deformed by high temp just above R28 and R29. I also hear some stertorous noise when main power cord is plugged into UPS. How to fix that? Thanks. at 26.06.2009 16:29

RS500s overheating I forgot to mention, there are different dates on PC Bs, older one is APC C 2001 08/03/2002 640-0259_REV05 and second one is APC C 2004 640-0259A_REV06, both have same issue and newer one overheated more. at 26.06.2009 16:35

Overheating problems Sorry, but I can't help you here. I have a few RS500, but all of them are working and in continous use. It isn't easy for anyone to tell what is wrong with your units, but if someone has experience with this spesific problem, please send me some text and photos and I could add them to the blog. Stig Vidar Hovland at 26.06.2009 22:54

Inductor buzz driving me nuts I bought one of these last week and i already want to throw it away. The buzz is killing me any sugestions? Would realy apreciate it. Thanks at 18.07.2009 05:53

same problem but no power indicator on i have the same problem, but i have bought a new one, prolink ups. when i read your post, i tried to fix the problem. first thing that i do is plug the power cable and turn on the power. but no sign of power on (no lights on). do you think that if i replace the capacitor, ill fix all the problem?? please reply, i really need your help. thanks at 30.08.2009 20:24

back ups ra500 up side very hot one of place] how i repaire at 06.09.2009 08:56

Thank you very much i've repaired 2 unit (same symtom) and it work like a new one, by replaced all cap (85->105c) i hope it won't need any cap replacement again for 2-3 years :D at 12.09.2009 09:39

Similar to .... CS 650 APC noisy resistor buzz I wish I had the same fault..... Got a new C S 650 that is driving me crazy with the charger control circuit with audible noise. You wouldn't believe it but the noise is comming from a RESISTOR # R3 on this rev6 board. (March 2008) I've never heard of a resistor making this much noise. Has any tech experienced this - however works yet it produces high frequency noise. Weird. C apacitors - chokes are fine. at 04.10.2009 11:38

More radical modification Well, designers of this circuits were… (censored) I have had the same problem, analyzed the switching power supply and found the same problem. C onsulting the data sheet of UC 3842B, the 22µF capacitor seems to be underestimated. At least in RS500 230V version REV05 one of resistor around eats permanently about 2 Watts and generates a lot of heat. That is why I decided to do a more radical change: Replace the capacitor with much larger one: 220µF. Remove the parallel 3.3kΩ resistor R139 without any replacement. Replace large hot 50kΩ resistor R28 by 220kΩ of the same size (probably even more is possible).

It decreases power current by 2 Watts and temperature there by 40°C at cost of 1 second delay after connecting the power plug. Purpose of such modification: Original design used a very hard divisor that divides the plug voltage to supply ~10mA. It is nearly enough for running the oscillator, so 22µF was (nearly) enough. But the divisor should be used just to start oscillation. Once the oscillator runs, it is powered from the transformer and the divisor is not needed. You can verify this fact by disconnecting the large divisor resistor, touch, and remove. Oscillator runs. The datasheet says, that when there is no power to run oscillator, the IC eats less than 0.5mA. It means, that the divisor could be designed to provide only 0.5mA, not 10mA. In this case, capacitor must be larger (e. g. 220µF), because the complete start of the oscillator is powered nearly exclusively from it. It must have enough juice to keep voltage above the minimal voltage until the transformer start to give power. Happy hacking Stanislav, http://www.penguin.cz/~utx/ at 08.11.2009 01:13

A zillion thanks!! Following an overnight power surge I noticed in the morning the three lower leds flashing continuously and no backup power. So I soldered off of an old pentiumII motherboard a 16V 22µF 105C capacitor and replaced the one shown in this tutorial. I plugged in and for a few seconds the three lower leds flashed till the power on (green) led lit (I guess meaning that the battery was completely uncharged and now it is charging). Many thanks again at 08.11.2009 12:36

More radical modification documented Hallo. I just documented my more radical modification described above: http://www.penguin.cz/~utx/apc-ups/ Apropos, if anybody is able to read values on R138 and R150, please let me know. My UPS had them damaged so it was imposible to measure them or read the value. They are replaced by 10R on my images, but I am not sure, whether it is correct. Thanks, Stanislav at 09.11.2009 00:28

RS 500 is in the second life!

RS 500 is in the second life! Hallo, Thanks a lot for this repair instruction - the best I've ever seen! My RS 500 is now working again, I used a capacitor with 47uF/16V because it was sunday and there was no original capacitor in my box. RS500 runs very well with 47uF! best regards, Bill from Germany at 13.11.2009 22:25

Lot of thanks We have the same problem ,it was not charging the battery so i have seen your procedure for repairing and now it is up to the mark Another thing plz tell us the specification of Resistor R28 in circuit boared of UPS .

Junaid at 23.12.2009 06:36

Thank you twice.. I had two apc 500 units with this problem, both of them are fine thanks to you! So thank you twice! Alkis from Athens, Greece at 22.01.2010 14:59

Thanks and thanks. Newer version of RS 500 unit with 50V 22uF capacitor fixed with replacement from an old Base10-T network card. at 30.01.2010 11:57

Thanks !! 100uF/35V 105C Works :-) Matony at 11.02.2010 07:23

suwat Thanks a lot. My APC BR500i work again. at 25.03.2010 14:38

lost battery backup output

Last month, during a power failure I plugged my APC BE500U-C N into a120V generator that has the ground potential of 40V and now it started beeping, and does not offer any battery backup power. The battery measures 13Volts AND THE units battery charging leads show 13.5V with battery removed. any ideas how to fix? at 30.04.2010 15:56

rs 500 alarm C ould somebody tell how to disable the alarm in this model... apc rs 500... take in account that I not an engineer....thanks [email protected] at 12.05.2010 14:48

Hello Following an overnight power surge I noticed in the morning the three lower leds flashing continuously and no backup power. So I soldered off of an old pentiumII motherboard a 16V 22µF 105C capacitor and replaced the one shown in this tutorial ( I plugged in and for a few seconds the three lower leds flashed till the power on (green) led lit (I guess meaning that the battery was completely uncharged and now it is charging). at 14.05.2010 12:11

resistance value Kindly tell the value of resistance R28. at 12.06.2010 12:30

resistor value R28 = 56K at 15.06.2010 03:17

RESISTOR KINDLY THE VALUE OF R26 at 22.06.2010 12:25

resistor resistance value R29 email at [email protected] at 22.06.2010 13:35

APS CS 500, always "On Battery", can't turn off It is a very nice tutorial. I found it when i did a research about repairing my C S 500. When the unit is connected on power source there is a yellow light "On battery", even when there is no

When the unit is connected on power source there is a yellow light "On battery", even when there is no battery inside. The unit won't turn off. Do u have any idea what i should do? Thanks in advance. at 03.08.2010 12:38

Resistor values apc RS 500 Thanks for the nice tutorial and great solution to my problematic rs 500. I would like to help some other users and publish values of resistors that may be erased because of overheating. R28 = 50K 2W 5%, R29=3,3K 2W, R75=2,2R 2W, R157=20R 1/4W. at 17.09.2010 12:02

Thanks my friend!! I just replasced the capasitor and the r28 resistor and it works! at 02.10.2010 14:44

Graciassss Excelente tutorial, recupere 2 UPS. at 04.10.2010 19:06

overload Hi, I have have a UPS APC C S500, and in this moment it is on OVERLOAD state. at 19.10.2010 20:16

thanks! I have just repaired my ups using your instructions. at 20.10.2010 18:45

UPS APC RS1500 Overload Hi, I have have a UPS APC RS1500, and in this moment it is on OVERLOAD state. how i repaire at 06.12.2010 17:20

A zillion thanks AGAIN!! Almost one year following heimes' instructions, [comment 8.11.2009: A zillion thanks!! Following an overnight power surge I noticed......uncharged and now it is charging). Many thanks again], my rs500 died again!!! I followed the more radical modification http://www.penguin.cz/~utx/hardware/APC _UPS_RS-500/ and guess what: It's ALIVE again (cost