Heime

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.

Thanks, fabulous tip, I above thank for you and the people like You Ricardo

It worked like a charm i replaced it with a 22uF x 25V 85°C Capacitor it works!! Now i have to check if the battery is dead... Thank you a lot

thanks, my RS 500 again live.
Mirob, Slovakia

Same problem here!!! Thanks for the tip, I'll fetch the soldering iron ASAP 8-)

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.

muy buena solucion hace meses que buscaba la solucion.
Gracias ( thanks you)

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.
Clarence
Southwest Monitors & Printers POS
SWMP@VERIZON.NET

I LEAVE IN INDONESIA, I HAVE SOME TROUBLE WITH MY RS500, NOW WITH YOUR BLOG, MY RS500 WA COME BACK AGAIN....
I REPLACE WITH SAME  CAPASITOR 22uf 16v 85c.
MAY BE, I WANT TO RE-REPLACE WITH 105c CAPACITOR FOR LONG LIFE COMPONENT. THX FOR U ALL.

I WANT TO RE-VIEW OR TRANSLATE TO INDONESIAN LANGUAGE WITH COMPLATE U'R PHOTO IN MY BLOG, I WILL PUT YOUR LINK, FOR ORIGINALITY SOURCE. THX U.


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

Cured 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.

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 !!!!!!!!

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 !!!!!!!!

The C7 had used a 50V 22uF 105c with unknown manufacturer.
Other caps are gold color Jamicon.

Este tutorial es excelente, le cambié a 4 UPSs el condensador y están cargando perfectamente.

Gracias de nuevo.

Hello
My name is Willan
Can 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

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

Excellent fix!! I was just about to buy a replacement UPS. Many thanks.

Neville      UK

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

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?

Indeed works.

Thanks

Congratulations 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?

Thanks from Finland friends.

I have one exactly the same problem and the capacitor replacement indeed fix the problem.

regards,
john_t
Subic Bay, Philippines.

BCB was burned around R28 of my APC, even plastic case was bit melted

My UPS disarching battery, what problem?

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 <at> hotmail.com

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.

Hello, I have same issue with overheating, I have two RS500 with smoked top and PCB, 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.

I forgot to mention, there are different dates on PCBs, older one is APC C2001 08/03/2002 640-0259_REV05 and second one is APC C2004 640-0259A_REV06, both have same issue and newer one overheated more.

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.

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

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

up side very hot one of place]

how i repaire

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

I wish I had the same fault.....
Got a new CS 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.

Capacitors  - chokes are fine.

Well, designers of this circuits were… (censored)

I have had the same problem, analyzed the switching power supply and found the same problem. Consulting the data sheet of UC3842B, 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/

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

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

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

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

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

Newer version of RS 500 unit with 50V 22uF capacitor fixed with replacement from an old Base10-T network card.

100uF/35V 105C Works :-)

Matony

Thanks a lot. My APC BR500i work again.

Last month, during a power failure I plugged my APC BE500U-CN 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?

Could somebody tell how to disable the alarm in this model... apc  rs 500... take in account that I not an engineer....thanks

dapal55@yahoo.es

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).

Kindly tell the value of resistance R28.

R28 = 56K

KINDLY THE VALUE OF R26

resistance value R29 email at peweelocsin@yahoo.com

It is a very nice tutorial. I found it when i did a research about repairing my CS 500.

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.