Need help identifying transformer - Page 1
Forum section: electronics / general

author: jbomba
author_rank: Contributor
timestamp: October 25, 2012, 11:34:47 am
content: Hi im trying to identify the transformer on this pcb the only markings on it are on the side which says 08114 ive run a google search and have been unable to have a hit on it i have also desoldered the transformer and found a b12 marking on the base. this transformer is whats busted on the pcb aswell as the bridge rectifier a new board is $450 so id really like to fix this one ive attached the photo. By the way it is an inverter board from an air conditionerUploaded withImageShack.us

author: Kevin.D
author_rank: Frequent Contributor
timestamp: October 25, 2012, 11:56:20 am
content: What do you mean by busted ? shorted turns ? open winding ? .It looks to be very easy to rewind so why dont you do that ,then it doesnt matter what marking's are on it.Just ensure you use same guage enamelled wire and same number of turns.

author: jbomba
author_rank: Contributor
timestamp: October 25, 2012, 12:11:56 pm
content: it was open. im quite new to electronics so will give rewinding a go are there rewind kits you can purchase with a wire gauge?

author: Psi
author_rank: Super Contributor
timestamp: October 25, 2012, 12:26:07 pm
content: are you sure its not a mains filter?

author: jbomba
author_rank: Contributor
timestamp: October 25, 2012, 12:33:54 pm
content: the component? not too sure just looks like a transformer too me has 2 coils if that helps

author: jbomba
author_rank: Contributor
timestamp: October 25, 2012, 12:39:21 pm
content: the board powers inverter compressor and dc fan motor

author: Fraser
author_rank: Super Contributor
timestamp: October 25, 2012, 12:53:54 pm
content: If you are talking about the item that has the marking "L2" (meaning inductive component 2, NOT transformer 2 as that would likely be T2 or TR2) adjacent to it and looks to have two copper windings in a side by side configuration, that is a common mode input filter and each winding is IN SERIES with the live and neutral supply lines. If you tested it like a transformer with primary pins on one side and secondary on the other.....it would appear to be open circuit. Test one pin against its partner on the opposite side....I reckon you will have continuityL2 does not look burnt up to me.Take alook at this page for details regarding common mode filters or just google teh term "common mode filter":http://www.exergia.info/Lightning/lightning7.htmA failed rectifier may not be you only fault on this PSU....it's often another component down the line such as a reservoir capacitor or the switching transistor. If you are not experienced in switching power supplies, please be very careful as the voltages on the input side range from painfull to deadly. You should do some reading on SMPSU's before attempting to repair one. IMHO they are far more challenging and dangerous to the inexperienced technician than simpler linear PSU's.Good luckFraser

author: jbomba
author_rank: Contributor
timestamp: October 25, 2012, 09:33:31 pm
content: Hi thanks for your help you are certainly right it is a mode filter. Im definetely a noob when it comes to this , anyhow i think the mode filter may just be the culprit here. However i am going to replace the bridge rectifier aswell. Its looks as if the wire from one coil of the mode filter has broken and shorted with the PCB. I will be checking all other components on the pcb aswell before i return it back into a test air conditioner. I absolutely hate the wastefulness in the Aircon Industry . The ammount of PCB's that just get thrown away when one $3 part has failed. Alot of these PCB'S cost in excess of $1500 aswell.Ive attached a pic of underneath the mode filter to show what i mean.Now my next question is how do i go about sizing one of these mode filters. I have found a very similar looking one on ebay. I know that just because it looks the same doesnt mean a thing however heres the link for it here. I have a brandnew spare for this PCB so i could remove a good one and do some tests if there are any to help identify it.http://www.ebay.com/itm/Inductor-2mH-common-mode-line-filter-UU9-8-2mH-5pcs-/160901593151?pt=LH_DefaultDomain_0&hash=item25767b783fUploaded withImageShack.us

author: Thor-Arne
author_rank: Unknown
timestamp: October 25, 2012, 10:28:47 pm
content: Quote from: jbomba on October 25, 2012, 09:33:31 pmI suppose that mark on the pcb is from the coil and rectifier shorted?If that's the case, be sure to check the other parts that's connected to that rectifier.When you assemble it again, clean the pcb well. and blob in a nice amount of silicone perhaps. (to avoid more shorts).A pic of the backside would me nice to, and of course a schematic.

author: jbomba
author_rank: Contributor
timestamp: October 25, 2012, 10:56:03 pm
content: Unfortunately the manufacturers do not supply schematic drawings of the pcb components. Ive attached another pic of top and bottom of board the blue pen pointing at the 4 pins of the mode filter.Uploaded withImageShack.usUploaded withImageShack.us

author: Thor-Arne
author_rank: Unknown
timestamp: October 26, 2012, 07:24:05 am
content: What are those white dirt markings? Have the board been wet or is it from the manufacturing process?I suggest that you clean the pcb properly before applying any power to it.

author: jbomba
author_rank: Contributor
timestamp: October 26, 2012, 08:17:28 am
content: white marks are heat sink paste. Also board has a coating on it to help prevent shorts from moisture and insects

author: jbomba
author_rank: Contributor
timestamp: October 26, 2012, 08:21:13 am
content: can anyone think of a way to work out what the specs of the mode line filter might be?

author: Fraser
author_rank: Super Contributor
timestamp: October 26, 2012, 01:27:18 pm
content: IMHO any common mode filter that is designed for mains power usage, and that has the same thickness of copper wire (i.e the current rating) will suit the requirements of your board. I would not expect that PCB to draw significant current through the common mode filter anyway. Check the fuse rating in the live feed and just find a common mode mains filter that can cope with 150% of that current. If its a 1A fuse fit a 1.5A filter and so on. Many modern Switch Mode power supplies contain such a filter so you may be able to salvage one from an old PC power supply if things get desperate. These filters are not a precision product so it is one component that is safe to change out provided you replace it with one that has the same or better voltage and current handling.Looking at the botton of the PCB and the pattern of the smoke marking, I believe that the bridge rectifier has had catastrophic failure during which molten material has shot out of one end and coated the PCB. Make sure you clean those marks off as they are likely conductive if metal particles are present. You mention the possibility that one of the common mode filter wires touched something...any more detail on that please as it's a very odd failure mode for such a filter.RegardsFraser

author: jbomba
author_rank: Contributor
timestamp: October 26, 2012, 10:43:29 pm
content: Hi to mee it just looked like the wire on one of the legs of the mode filter just broke. Icould be wrong however im going to change both and also desolder the transistor and check if its faulty

author: jbomba
author_rank: Contributor
timestamp: October 27, 2012, 09:30:05 pm
content: ok ive found some suitable line filters just wondering if someone could explain what the mH rating is

author: SeanB
author_rank: Super Contributor
timestamp: October 28, 2012, 06:29:59 am
content: Inductance of the coils. Not a worry in this application as long as it physically fits the pin spacing. If you look often this is just replaced with a pair of wire links.

author: jbomba
author_rank: Contributor
timestamp: October 28, 2012, 07:23:21 am
content: ok cool thanks for all your help im away at work for a few weeks yet but ill keep you posted on how i go

author: David_AVD
author_rank: Super Contributor
timestamp: October 28, 2012, 12:01:17 pm
content: [mini rant]Just a side note; if the front end of that circuit was traced out even just a little, it would have been apparent that the device was not a transformer. (in series with the current path, not in parallel)I do realise deductive reasoning is a learnt process, but too few people seem to place much importance on it.Geeze, I'm becoming grumpy in my middle age![/mini rant]

author: perfect_disturbance
author_rank: Regular Contributor
timestamp: October 28, 2012, 06:47:57 pm
content: Quote from: David_AVD on October 28, 2012, 12:01:17 pmI'm sure your right however for a person new to electronics they may trace out the circuit and be even more confused if they have never seen a filter like this before. I'm pretty sure I would be.