Hitachi lithium battery charger question. - Page 1
Forum section: electronics / general

author: Unknown
author_rank: Unknown
timestamp: September 24, 2013, 03:12:21 am
content: Hola,have an Hitachi UC 18YKL Li-ion, Ni-MH and Ni-Cd battery charger which as far as I know, overheated and failed due to it being connected to 127V instead of 230V.The chargers internal 3.15A fuse didn't blow, however one of the 2W resistors heated so much that it came off (and burned) the board, as well as causing the plastic housing to start to melt and malform. The resistor still reads 130 Ohms even though it has no colour. -See attachments. The scorched bit of board is where the resistor lived. The last 2 pics are of the fuse with it's cover removed and sand.Before I start removing and testing each and every component, by some miracle, does anyone have a schematic for one of these, or perhaps have experience with this problem?Clearer pics can be taken in the morning.

author: SeanB
author_rank: Super Contributor
timestamp: September 24, 2013, 06:40:16 am
content: Don't think running off 127V caused that. most likely the resistir was undderrated in the first place. As the primary side has not failed ( the fuse is intact, the bridge and other power semiconductors there are still in the cases and not blown to bits) most likely the resistor simply overheated, drifted high in value ( probably it should be a 10R or 1R resistor like the companion one) and this then increased the dissipation to the point where it burnt out the board. Likely you just have to replace it with a 5W unit and clean up the carbonised board and replace the traces under the board where they are going to be affected.

author: Unknown
author_rank: Unknown
timestamp: September 24, 2013, 04:31:25 pm
content: Just wrote a long, half hour post which didn't post and just wasted my time and now I have to go out.What I had said was that I didn't think it was a 1 or 10 Ohm as the bands on the burnt resistor are Brown or Red, (something light), Brown or Red and the resistor reading is 134.5 Ohms. (Brown, Orange or Yellow, Brown?)Next, in foto 1, in the bottom left is FET 2 which is dead short between Drain and Source (looks like 'W2K 3' written on it).Unless someone has a smart idea, we are probably gonna need the schematic.But Sean, gonna try with a 120 Ohm 5W and see if that helps but am also gonna start pulling components around the scorched area.Thanks for the input.

author: ResR
author_rank: Regular Contributor
timestamp: September 24, 2013, 07:39:12 pm
content: BAT 754 is W2K.BAT-754 Digikey linkIt looks like secondary side failure, resistor overheated, overloaded resistors are common mistakes manufactures do occasionally. Sometimes switching power supplies can take both 127V and 230V with almost no secondary voltage drop, although with less power capapility, for example TOP-22x based PSU.

author: Unknown
author_rank: Unknown
timestamp: September 25, 2013, 12:52:49 am
content: Thanks ResR,every day's a school day! No Drain or Source...now the fun part of trying to find one in Rio.Bought a 120 Ohm 2W today to try, but it's late here now so that will have to wait til I find the BAT 754. Tomorrow hopefully.No-one here has an Hitachi drill?Maybe I should just open a new post with that question as the title?

author: DBNLight
author_rank: Newbie
timestamp: July 17, 2014, 10:17:40 am
content: The resistor, R9 is 10 Ohms