HELP repairing a UPS that doesn't power off

[azigta]

Hi, I'm trying to repair a UPS that doesn't power off. The ups model is MGE ellipse premium 650. This is an image of the pcb board (will make references to it) The manual can be found here

At first it didn't even power on at all, nothing happened when plugged to the mains, nothing happened when actuating the on/off switch.

It had a dpdt "push and release" type switch (can be seen in the attached image) that it was not doing the job properly so I changed it to a dpdt lever type switch. And after checking the connections and making sure that it was doing the contact correctly, I powered it on and it gave me a battery alert sign through some lights that are built in the ups.

I charged the batteries with the same ups, unplugged, and plugged the thing again, and the alert went off.

For that moment on, the lever type switch didn't do anything, but the ups worked since it actuated the battery circuit when unplugged.

At first I checked the output voltage and my tester says it's 180-182v but I've read that if my tester isn't "true rms" it's going to read that value if the ups's output isn't a pure sine wave. However, the manual doesn't say anything about if it's pure wave or not so for the moment I have not tested if it can power up a pc power supply.

It charges the 2 batteries that it has in series with no problem, and when I disconnect it from the mains , the relays click and the ups activates the circuit.

So I tested 2 voltage regulators that are next to the switch but they were ok so I kept searching and I found that there's an IC that controls a bunch of things along with the soft start/soft stop  circuit. That IC is a SG3525A.

I soldered a 16 pin socket onto the board and ordered the IC on ebay.

The IC arrived today and now I can power ON the ups with the switch (when is not plugged to the mains), but I can't power it off. The only way to power off the thing is by disconnecting the negative pole on the batteries and disconnecting it from the mains.

If you look at the image, the SG3525A is the little 16 pin IC that is at the bottom next to a white capacitor on the left (that I also had to replace because I broke it when I removed the bad IC) and next to the old, now replaced, switch.

If you keep looking at the left side of the switch, you can see 2 voltage regulators, I've tested them and they are ok.

The big IC has a sticker on the top of it and I can't see the model number,but I don't know how to test it either

Also I wanted to say that I don't have a variable power supply and I would appreciate if someone could send me a link to an schematic for building one that can go up to 24v DC at least so I can test relays/mosfets just in case some of them are bad. I have a big variety of electronic components, so I'm sure I can build a variable power supply, but I'm not an engineer and without an schematic with component list and pcb print design (obviously single layer only) I can't make pretty much anything. I don't have a single smd component so If anyone knows about a good through hole component schematic for this kind of project I would highly appreciate it.

Maybe someone here can help me out with this, because I've ran out of ideas. I'm a 20 years old student that likes to repair things but sometimes due to a lack of knowledge and things like not having a variable power supply, I can't proceed. Maybe someone here can tell me what should I test next...

I'm not a native english speaker so excuse me if I made mistakes when writing this

Thanks

[singapol]

Your english is fine so don't worry. As you know this product is not meant to be repaired by user..it says if red LED light turns on to call for service. If you like to repair things then treat this as a lesson or practice.

Well the first thing is to note what the UPS indicate by way of LED status lights and beeping sound.Then refer to user manual for explaination.Below is from page 2:

Theory of Operation
Ellipse Premium is a line interactive UPS
which normally operates in the bypass
mode. Surge suppression and filtering are
also provided in this mode.

The UPS transfers on boost mode in the
event of input voltage drop. This operation is
provided from 84 V to 100 V input voltage.
The UPS transfers the load quickly to the
battery when a power failure occurs. If the
power returns before the battery is
exhausted, the operation returns to normal
and the battery is recharged.
The Ellipse Premium UPS is comprised of
three major systems: the inverter, the battery
charger/ battery and the bypass.
All logic and supervision in the UPS are
provided by a state-of-the-art microcontroller.

Inverter
The inverter is the heart of the UPS and
inverts direct current (DC) from the battery
into alternating current (AC) at 120 volts.
The DC voltage from the batteries is
switched on and off at a high frequency and
transformed to a higher voltage (DC to DC
conversion). After conversion, the high
voltage is converted into a pseudo-sine
wave by a pulse width modulated (PWM)
inverter to 120 volts AC RMS. This unique
MGE technique, eliminates all bulky 60 HZ
components and reduces size, heat, and
greatly enhances reliability.

Battery Charger/Battery
The battery charger maintains the battery
and the battery provides the source of backup
energy when a power failure occurs. The
battery charger converts 120 volt AC utility
power to filtered and regulated DC specific
for battery charging. The battery is a
recombinant, sealed, lead acid-type which
provides the high current required for UPS
use and long life. It requires no additions of
water during its life.

Bypass
The bypass is the electro-mechanical
hardware providing a transfer to or from the
inverter. This is done rapidly and
synchronized to the utility power sine wave
in order to provide continuity to the PC and
not cause a re-boot.
E N G L I S H
MGE

This UPS is controlled by MCU (microcontroller) it uses logic ic or gates to activate actions. Eveything is
interlinked. I would suspect the BYPASS circuit and check from there. It outputs a pseudo sinewave/clipped sinewave so I think your meter should give average measurement,that said your measurement is high when you should expect 110  AC volts output ? Good luck.

PS: There seems to be a diagnostic software (Solution pac) page3 you can download from MGE website.

[azigta]

This UPS is controlled by MCU (microcontroller) it uses logic ic or gates to activate actions. Eveything is
interlinked. I would suspect the BYPASS circuit and check from there. It outputs a pseudo sinewave/clipped sinewave so I think your meter should give average measurement,that said your measurement is high when you should expect 110  AC volts output ? Good luck.

PS: There seems to be a diagnostic software (Solution pac) page3 you can download from MGE website.

I shouldn't expect 110 ac volts on the output since here we use 220 or 230v . The wall outputs 230v but 4 years ago or something like that, it was 220 so it could output 220 since I think this thing is not less than 4 years old.

The problem is that it doesn't turn off, all the bypass circuit seems to be working fine. It just doesn't turn off. I will test it with a pc power supply to see if it can power it up but I don't think any software could help me with this since there's a physical switch that should turn it off and it doesn't. So I don't think this can be solved with any diagnostic software because if I connect it to a pc it should tell me that it's working fine, because it is in that sense,  all the lights and beeps are working as spected, beep duration delay and lights are giving me the sign that everything is working as it should.

I will re-check the switch that I soldered and I will try to search some information about that big Ic maybe it controls part of the shutdown process. Anyway thank you for your answer

[singapol]

This UPS is controlled by MCU (microcontroller) it uses logic ic or gates to activate actions. Eveything is
interlinked. I would suspect the BYPASS circuit and check from there. It outputs a pseudo sinewave/clipped sinewave so I think your meter should give average measurement,that said your measurement is high when you should expect 110  AC volts output ? Good luck.

PS: There seems to be a diagnostic software (Solution pac) page3 you can download from MGE website.

I shouldn't expect 110 ac volts on the output since here we use 220 or 230v . The wall outputs 230v but 4 years ago or something like that, it was 220 so it could output 220 since I think this thing is not less than 4 years old.

The problem is that it doesn't turn off, all the bypass circuit seems to be working fine. It just doesn't turn off. I will test it with a pc power supply to see if it can power it up but I don't think any software could help me with this since there's a physical switch that should turn it off and it doesn't. So I don't think this can be solved with any diagnostic software because if I connect it to a pc it should tell me that it's working fine, because it is in that sense,  all the lights and beeps are working as spected, beep duration delay and lights are giving me the sign that everything is working as it should.

I will re-check the switch that I soldered and I will try to search some information about that big Ic maybe it controls part of the shutdown process. Anyway thank you for your answer

Take note that unless UPS is designed for international market this unit could be for china's domestic market which uses 220Vac. The big ic you mentioned is probably a 42pin microcontroler (pin pitch to close to count!) perhaps a japanese or european brand in which case you can trace the I/O pins to where they connect?

PS:Clue-There is a blue ceramic clock resonator at G1 or C1 at the bottom of this big ic. Also described in user manual that it is MCU controlled.

[rch]

I presume the dpdt switch you added is not a momentary contact one, so I hope you are turning it off again having started the UPS.  It could interfere with operation if left closed.

Edit:   I am assuming the push switch is momentary, reading what you said it probably isn't.  So ignore my comment!

[azigta]

I presume the dpdt switch you added is not a momentary contact one, so I hope you are turning it off again having started the UPS.  It could interfere with operation if left closed.

Edit:   I am assuming the push switch is momentary, reading what you said it probably isn't.  So ignore my comment!

Hi, thank you for your help, I will check the switch when I have a little bit of time. Every comment is appreciated, so I won't ignore yours. Thanks