Help with repair of an APC SMT3000 - Page 1
Forum section: electronics / repair

author: alex_pescaru
author_rank: Contributor
timestamp: July 24, 2022, 06:59:49 am
content: Hello,I have an APC SMT3000 UPS that at some point started to behave strangely.One day I've seen that the voltage on the battery string, with the battery connected, is about 48v instead of 54v.I've thought that could be some glitch on the UPS charger firmware and I've performed a "cold reset" and after that it said on the display Error: Charger.Now we getting something... After that I've tried to see if the UPS is still functioning from inverter point of view and when disconnecting the 220v power and switching to inverter, the FETs from the BLACK side of the transformer (H-bridge) blew with a nice show of light and sound.I've dismantled all the FETs and when I've measured with an ohmmeter the outputs of the HIP4082 driver, I've also seen that the driving outputs for the side with blew FETs are showing a quite small impedance versus ground. About 80 ohms versus about 7 megohms the other outputs. Therefore I've also de-soldered the HIP4082 and mark it as defective.In this moment, with the board on the table, without any FETs and HIP4082, I've connected the 48V battery to the board and measured some things.Ignoring the error messages from the display, it seem that the outputs (L1OUT, U1OUT, L2OUT, U2OUT) from the IC21 that drives the HIP4082 are alright (I think...).On idle, it seems that only 2 of the above 4 signals are active, some 24kHz narrow pulses. I am thinking for charging the battery as this UPS is using the inverter in the reverse configuration for charging.When I am trying an UPS test from the display, the above 4 signals are all activating and have some 50Hz square signal on them. Of course, after 1-2 seconds the test halts with an error, probably because of lack of feedback - remember 4082 and fets missing.Is all of the above correct?I've ordered an HIP4082 and 16 FETs. I didn't find IRFB4710 and I've ordered IRFB4410.IRFB4410 seems to be a little better from all points of view, gate capacity, rise/fall times, DS resistance, etc.In your opinion, IRFB4410 are OK?What more should I check? I've checked all relays, relays' transistors, various other diodes, transistors, etc.After soldering the new components, what should I check more or how should I proceed in order to not blow up these new components if anything else is defective?Do you have a schematic for this 2U3K 640-3080 rev04 board? Or something equivalent?Many thanks in advance!

author: alex_pescaru
author_rank: Contributor
timestamp: July 29, 2022, 05:35:51 pm
content: UPS repaired now, with all the questions in the above post answered.

author: asis
author_rank: Frequent Contributor
timestamp: July 30, 2022, 04:21:39 am
content: Hi Alex,You did everything right.Congratulations!

author: alex_pescaru
author_rank: Contributor
timestamp: July 30, 2022, 11:49:21 am
content: Thank you Vladimir.Your advice has helped me a lot.

author: Muhammad Ehtesham
author_rank: Newbie
timestamp: October 18, 2023, 06:51:38 am
content: Please help me my 2U3K 640-3080_REV04 Display ic damage please what is this name and number ic

author: asis
author_rank: Frequent Contributor
timestamp: October 18, 2023, 10:22:24 am
content: Hi,IC18 - MOSFE'S control driver.Works with IC19 (ON-semi 361-0015G ASIC); IC21 (ON-semi 361-0025V2 ASIC)https://datasheetspdf.com/pdf/1472908/Renesas/HIP4082IPZ/1https://www.alldatasheet.com/view_datasheet.jsp?Searchword=4082IBZC