Fixing ups , what know what number of this component. - Page 1
Forum section: electronics / repair

author: nquantum
author_rank: Regular Contributor
timestamp: April 25, 2020, 01:00:14 pm
content: Try to fix apc ups 1400. It seem this component seem black at their leg. Unfortunately I don't know don't sure what part number is pls help me. The second picture is compare to another component in same board. Their leg look normal.

author: madires
author_rank: Super Contributor
timestamp: April 25, 2020, 02:42:55 pm
content: It's a TL1431, a more precise version of the TL431.

author: nquantum
author_rank: Regular Contributor
timestamp: April 25, 2020, 03:07:55 pm
content: Thank! Lot at it leg. It seem that it burn somehow compare to another in same board.

author: madires
author_rank: Super Contributor
timestamp: April 25, 2020, 03:20:34 pm
content: The legs are tarnished, but that doesn't mean the IC is bad. Download the datasheet for the pinout and check the output voltage.

author: TheMG
author_rank: Frequent Contributor
timestamp: April 25, 2020, 03:33:16 pm
content: Quote from: nquantum on April 25, 2020, 03:07:55 pmThat doesn't look burned, just looks like the leads have oxidized a bit.What are the symptoms? What's the UPS doing (or not doing)?

author: nquantum
author_rank: Regular Contributor
timestamp: April 26, 2020, 01:12:27 am
content: QuoteTrue! I will do that.QuoteNothing happen when I plugged_in. Normally there is relay sound once. And it will power on when pressed power switch. Now is nothing happen. Seem like there is no low voltage for control circuit. Just my guess only. I will check there is voltage charge battery or not after plugged.Tobe honest I not sure if I can fix it. Anyway better than just trow it away.

author: CrazyTiger
author_rank: Regular Contributor
timestamp: April 26, 2020, 02:03:00 am
content: Hi,have you verified the UPS battery?These UPS usually needs a charged battery to turn on, and if the battery is dead, the UPS will not turn on at all even if you plug it to the mains.

author: TheMG
author_rank: Frequent Contributor
timestamp: April 26, 2020, 02:26:24 am
content: As CrazyTiger mentioned, the battery needs to have a good voltage on it or the UPS will just play dead, even when plugged in to AC power.The reason is that in this UPS design, the control circuitry runs from the battery (and subsequently, the battery charging circuit). But it needs some initial power from the battery to start up and get the charging circuit going before it can power itself from AC mains.So definitely the first thing to check is the battery pack.

author: nquantum
author_rank: Regular Contributor
timestamp: April 26, 2020, 04:29:24 am
content: Quote.I will recheck that.

author: nquantum
author_rank: Regular Contributor
timestamp: April 27, 2020, 04:29:33 am
content: Update- Battery is working. Already check.- Disconnect transformer and AC plug only connect battery when press power button. I can read voltage input and output of regulator LM317 in picture. Only no beep sound no LED light.- connect transformer and AC plug read no charge voltage to battery (0v). It will not charge batt for sure.- no AC voltage at all reach the transformer. Seem to have problem with high voltage part.

author: nquantum
author_rank: Regular Contributor
timestamp: April 27, 2020, 07:39:39 am
content: Does this component is mosfet? Some how I search part number. Not sure what exact number. It seem to drive relays and it has around 10components across the board. Some of them I measure get weird resistance compare to each other.N09D7 ??

author: Manul
author_rank: Super Contributor
timestamp: April 27, 2020, 01:15:43 pm
content: Likely to be DDTC123XCA, but needs confirming. Not very likely to fail I would say.

author: TheMG
author_rank: Frequent Contributor
timestamp: April 28, 2020, 12:49:30 am
content: Quote from: nquantum on April 27, 2020, 04:29:33 amThat design of UPS uses the same transformer both for the AC inverter, and to provide power for the charging circuit.Thus, there is a relay which isolates the high voltage side of the transformer from AC mains, because you don't want the UPS to be back-feeding the mains (or giving AC power to itself) during a power outage. For safety reasons, this relay is normally-open and need to be energized to provide AC mains to the transformer.This is also why there needs to be a working battery in order to power the UPS on from a completely de-energized state. What happens is the microcontroller in the UPS will start up (from battery power), it will sense whether the UPS is connected to AC mains and whether or not the voltage and frequency are within range, then and ONLY then will it energize the relays to provide AC power to the transformer, and allow the charging circuit to work.Since you have good battery voltage, and presumably proper voltage out of the regulator supplying power to the microcontroller, then either the power button is bad, or the UPS is effectively "brain dead".

author: nquantum
author_rank: Regular Contributor
timestamp: April 28, 2020, 09:51:49 am
content: QuoteYes I can see it.QuoteRight. I track the 1st relay that is really isolate ac line into circuit. Normally after I plug in wallet I will hear sound of relay but now nothing happen.QuoteUnfortunate the power button is not bad. I read voltage out of regulator after I press power button. It just nothing happen after that press button. No LED, no sound, so any relay activity. And like you say. Since no relay switch then no voltage go to transformer either.And if you say "brain dead" mean microcontroller dead then I out of choice. Coz I will not find that with proper rom inside.I will try read if there is voltage power those ic or not.

author: nquantum
author_rank: Regular Contributor
timestamp: April 28, 2020, 11:32:27 am
content: vcc of ic 93LC46 EEPROM is 2.5v quite ripple.Is this look normal?And also when one probe touch there is some sound buzzer. It may from noise enter vcc line of ic.Those regulator LM317 in picture above have input 24v out 12v after power switch is press and flat not so ripple like the 2.5v

author: nquantum
author_rank: Regular Contributor
timestamp: April 28, 2020, 02:05:00 pm
content: updatevoltage vcc for ic is this.Quite clear there should be something wrong with supply voltage for these ic. So it microcontroller can not work.Try to find out why/what cause this.

author: nquantum
author_rank: Regular Contributor
timestamp: April 29, 2020, 11:52:56 am
content: I fix it already! It is LP2950 3.3v regulator for microcontroller.Like someone say "Nobody trips over mountains. It is the small pebble that causes you to stumble".

author: TheMG
author_rank: Frequent Contributor
timestamp: April 30, 2020, 12:32:22 am
content: Nice find! Unstable voltage to microcontroller would definitely cause a "brain dead" situation. Thus the first rule of troubleshooting: thou shall check voltages! But it's definitely harder to do when you don't have a schematic, as there can be a multitude of different voltage regulators in a given device.

author: nquantum
author_rank: Regular Contributor
timestamp: April 30, 2020, 02:45:50 am
content: QuoteYes. I will remember that thank!It true I track down high regulate voltage from 24v down to 12vall is normal then abnormal show at 3.3v. Trial and error until find it. At first i though cap is dead so I remove one near those regulator for 3.3v The scope show graph seem that 3.3v still not look good. Then either regulator or device draw much current. I go for regulator first coz i hear some sound and led already. Finally i got it the regulator.