APC SmartUPS overload

[Towney]

I am trying to save a 2014 SMT3000 that has just started showing overload with nothing plugged in.

What I know:
Turns on and charges batteries fine. Activate outlets and overload light comes on and display says 3780 watts, 4200 VA, and 42 amp. If still on utility power, there is 120 at rear outlets. If you go to battery it shuts off.

BradC (last post of linked thread)
https://www.eevblog.com/forum/repair/apc-smart-ups-1500-always-overload/msg1327907/#msg1327907
said SmartUPS uses current transformer, so I went looking for that and I have a brown and crusty transformer on what I think is the controller part of the board.

Labeled:
Class 130(B) SB14.2
APC 430 0731-Z
BCK EE25 7143B
Jingquanhua E208707
13 K 27 (this line is on the bottom face)

Label side has 4 pins, opposite side has 5 pins.

Can someone help me confirm if this is the problem, and if it seems likely, help me find a replacement?
This article seemed relevant,
https://www.mouser.com/pdfdocs/Coilcraft-Selecting-Currsent-Sensors-Transformers.pdf
but my experience level is more along the lines of replacing visually burned capacitors to save a TV.

Thanks

[Towney]

Three pictures together did not go through, let me try one...

[asis]

Hi,

Please write the model and version of the PCB.
The photo is not a current transformer.
It is a switching power supply that supplies power to all circuit components + 12VDC, + 24VDC, -9VDC
This PSU is powered by 24VDC. At least this applies to STM1500RMI PCB: 640-3081J-Z-001.
Current Transformer are indexed as "CT1", "CT2"

CT1:
JKT PH 1725
460-0006A-Z
JKT PH 1725
460-0006A-Z

CT2:
130B-1 SBI4.2
APC 460-1003-Z-001
HGQ-EI19-96
17F27
They are located in the primary AC supply circuit:
CT2 ~ Line;
CT1 ~ Neutral.
The photo shows both.

[Towney]

PCB is
Smart 4.5G 640-3077c  Rev. 11

CT1 and CT2 do have the 460 prefix numbers asis posted, are the other numbers you listed alternate manufacturers?

Battery reads 50.2 volts when offline, and 54.2 when online.

[asis]

Judging by the voltage drop when operating from the battery and the date of the UPS release, there is only one advice - it's time to change the battery.
After replacing the battery, a calibration is required from the control panel, indicating that
new batteries are installed.

[Towney]

Granted, the age implies new batteries...
but from what I have read, there is a bad battery light, and an overload light. It seems the overload with no load is a hardware issue.
I pulled and separated the batteries and two read 12.9 and two read 13.0.
Also, updated the firmware and turned off the self test function.
Still reads overload when booted up, with batteries or without.

[BradC]

You have a 4.5G unit. I only have a schematic for a much older unit, but APC didn't seem to make wild changes between generations, so have a poke based on this and see how you get on.

CT1 looks like current shaping to the charger/inverter ASIC. CT2 is likely to be the output current sensor. This is rectified and averaged, then fed into an ADC0838 on channel 5 (pin 6). Have a poke at that with a meter and see what sort of voltages you see. The earlier units had a pair of transformers which were used to sense the input and output voltage. I can't see those on your board, so I don't know how that works now, but the output voltage sense was used in conjunction with CT2 in what looks like an analogue multiplier to give the pwr-out signal.

I've avoided these newer units, so I don't have any experience with them. Is it indicating the correct input and output voltages? Try looking at pins 2 and 4 of the ADC (channels 1 & 3). Channel 1 is the input voltage, channel 3 is the output voltage. Generally if these don't match to a degree the UPS will issue a relay weld fault, but it's a starting point.

I make assumptions about the ADC only because APC appear to still be using the same 8051 based controller and firmware they've used since the 3rd gen and every single unit I've looked at was essentially the same. Have a poke around and see if there is an external ADC hooked up to the main MPU. I can't really be of any more help I'm afraid.

[TheMG]

This looks for all the world like a fault somewhere in the circuitry that processes the output from the CT.

Since the unit provides readouts of both watts and VA, I do not think the signal from the CT is averaged. It is likely amplified, maybe rectified, then passed along to an ADC or some kind of power measurement IC.

I would follow the traces from the output of the CT which measures the line output current, and see where that goes. It almost looks like an opamp circuit has gone open-loop and is hitting the rails or something like that. Could also be a break in the circuit somewhere leading to the CT output, that would cause it to pick up a rather significant stray AC voltage through capacitive coupling. There should also be some kind of a burden resistor on the CT output somewhere in the circuit, so do verify that is intact and connected.

I've avoided these newer units, so I don't have any experience with them.

Out of curiosity, any reason why? So far in my own experience I prefer these newer units to the older ones, they seem to be much easier on the batteries which last far longer than they ever did with the old units. They use a more reasonable charge voltage and also monitor battery temperature.

[BradC]

I've avoided these newer units, so I don't have any experience with them.

Out of curiosity, any reason why? So far in my own experience I prefer these newer units to the older ones, they seem to be much easier on the batteries which last far longer than they ever did with the old units. They use a more reasonable charge voltage and also monitor battery temperature.

Mainly because they haven't started popping up in Aus at reasonable prices second hand. I have schematics for most of the older units, and they are pretty easy to work on. The newer units also have a "veneer" processor to run the LCD which just gets in the way when talking to the actual UPS section. The SUA series were the first to temperature compensate the charge voltage. They can be adjusted in software whereas the earlier < 4G units need hardware adjustment. Either way, a quick tweak and the batteries live a long and happy life.

[asis]

It is possible that one of the relays is stuck, most likely RY900.
You check (compare) the state of the contacts of all relays with the PCB disconnected.
If something is stuck, for prevention, hit it with a screwdriver (with passion) and check again.

[Towney]

Thanks for all the input, but this one has crossed the bridge so to speak.
The relays checked OK with open/closed where they were supposed to be. I cycled them (relays on the board, but board removed from UPS) with 24 volt and they all seemed to open/close as expected.
Put it all back together again and with power online it started a new cycle of all four lights and failing power up. Display was on, but power did not pass through to the outlets like before. Attached batteries. It would try to power up and it displayed some AVR weld relay faults, and the previous power overload fault. Long story short, this time it fused the AVR windings in the transformers. When I took it apart the last time, the relays still are appropriate open/close, but when connected to transformer they all have continuity.
This one took the "nothing to lose" approach and I learned despite not repairing the machine.
This one looked like a single issue as a cause, and I think ultimately it was the controller. Who knows.

[asis]

When you test the relays by applying + 24VDC to them, you could damage the control circuit.
On this forum, I have already exhibited part of the circuit diagram, only for the STM1500RMI.
https://www.eevblog.com/forum/repair/smt3000rm2u-fault-findingrepair/

[brunoroselli]

PCB is
Smart 4.5G 640-3077c  Rev. 11

CT1 and CT2 do have the 460 prefix numbers asis posted, are the other numbers you listed alternate manufacturers?

Battery reads 50.2 volts when offline, and 54.2 when online.

Hi Guys, I need to know the technical documentation about the R266, R267 and IC19 of this PCB Smart 4.5G 640-3077c Rev.11

Can someone help me?

[BradC]

PCB is
Smart 4.5G 640-3077c  Rev. 11

CT1 and CT2 do have the 460 prefix numbers asis posted, are the other numbers you listed alternate manufacturers?

Battery reads 50.2 volts when offline, and 54.2 when online.

Hi Guys, I need to know the technical documentation about the R266, R267 and IC19 of this PCB Smart 4.5G 640-3077c Rev.11

Can someone help me?

Can you take some photos? Whole board, and then relative close ups of the parts in question preferably.

[brunoroselli]

Can you take some photos? Whole board, and then relative close ups of the parts in question preferably.

Hi, sorry for delay....

photos here....

[abdulbadii]

On battery doubt:
take out battery to get battery internal Resistance (BIR):
clip one of its terminal/pole the easier one, together with an end of R ~3-300 Ohm (depends on V_bat, Amp meter read quality) and one of the MM probe correctly  by use of an alligator clip
the other R end is gathered with the other  one of the MM probe correctly (+ red ,- black), touch it to the other battery end and read V on MM and write down!
subtract  this V from the MM-read battery's V
divide the result  by  this V / R whatever R is, depends on V_bat, Amp meter quality to read the V/R
so:

(V batt. - V on R ) / (V on R / R)

if this BIR is greater ~ 0.5 - 0.7 Ohm it's time to replace

On PS check its V, I output, on I reading use highest then lowest I range in the order
if not as specification;
V, may some faulty in T or R get (semi) open
I, cap. bad high ESR usually the first and last cap.

[asis]

Hi,

I might be of some help.
But, this is a different APC.

[thekidkevin93]

Hi,

I might be of some help.
But, this is a different APC.

Oh god. If my UPS is as similar as this one, than the IC was instantly fried the second I hooked it up backwards.
In the PDF the IC [IC19] has no protection what so ever.

All I got now is a steel case containing a 24v a non center-tapped stepup transformer, some power outlet sockets, and a 24v DC fan.

What a waste. I sure learned a lot and I'm going to learn more the right way by reading.

Any ideas what I could make out of this thing guys???