A little help with a chip - Page 1
Forum section: electronics / repair

author: freman
author_rank: Contributor
timestamp: September 23, 2019, 01:23:03 am
content: HiSo, my air-conditioner died, second one.Found a bug on the power supply of the ODU, it was fried (The bug and the power supply) - I have no idea why they don't conformally coat these boards, I know I will be when I'm done fixing it.Skid mark from this chip extends a good 4cm across the board - made it real easy to find.Most of the other components on this PCB seem dumb (transformer, caps, full bridge rectifier!!!, opto isolator) and otherwise unaffected so I'm going to cross my fingers and try replacing the chip.It's a Fairchild IC, it has a combination of markings in two different styles, lightly etched (white) and deeply etched (dark) makes it real hard to read.Top line is BDCAIBottom line is L156MRISI haven't been able to find any technical documentation on this chip, I also haven't been able to find anywhere (reputable) to buy this chip.The closest equivalent I can find by name is FSL156MRIN but without any technical data for the chip I don't know if it's a usable equivalent.Does anyone here have any ideas?Edit: jebus, just got the quote back to replace the board, $103.08 exMight be worth just gambling on ebay.

author: rsjsouza
author_rank: Super Contributor
timestamp: September 23, 2019, 01:45:30 am
content: Check the Fairchild FSL156MRI data sheet application circuit and trace the circuit around your board. There is a very high chance they will be very similar.https://www.onsemi.com/products/power-management/ac-dc-controllers-regulators/offline-regulators/fsl156mrinThese circuits are somewhat standard across the board - after all, it is a simple switching power supply.

author: amspire
author_rank: Super Contributor
timestamp: September 23, 2019, 01:47:45 am
content: FSL156MRIN is probably OK. The difference between the N and the S chip could be something like the temperature range and the N chip does -40 degC to +125 deg.A photo of the track layout of the board would help. Are pins 6, 7 and 8 shorted? Look at the application circuit in the datasheet and see if it basically matches the circuit on this board. If it does, it could be worth a go. The risk is that this chip is made in slightly different variants, and so the S chip could have something significantly different.Digikey have stock and the datasheet:https://www.digikey.com/product-detail/en/on-semiconductor/FSL156MRBN/FSL156MRBNOS-ND/3137109The is probably a zener in series with the optocoupler input on the secondary side of the transformer. Make sure it hasn't shorted.Richard.

author: freman
author_rank: Contributor
timestamp: September 23, 2019, 02:19:40 am
content: ThanksThat's basically the way I was leaning. I'll sit down with the FSL156MRIN datasheet and the PCB tonight and trace it out.I'll throw up photos from both sides of the board for those playing along at home.I didn't really intend to create this post today or I would have planned better (was hoping to come to work, spend half an hour googling and see what I could find that I couldn't yesterday).There's nothing that looks like much a zener anywhere on board, there's is a bunch of other diodes can check, I'll check the optocoupler too.Adding another picture I took earlier, ignore the necro action from the second bug, it figured it out and moved on shortly after the photo was taken.Edit: Got a part number for the samsung module, clearly this has been an issue they're encountering a lot because a lot of places I find this module to purchase someone has gobbed schmoo all over that chiphttps://www.sydneyappliance.com.au/SAMSUNG-AIR-CONDITIONER-MODULE-ASSY-DB92-02862AEdit edit: Wow, having a part number makes this much more funHere's both sides of the board - rip productivityhttps://www.repairclinic.com/PartDetail/Power-Supply-Board/DB92-02862A/3983638Edit^3: Not quite enough pixels in those pictures to figure it out without giving myself a headache, guess I'll have to wait till I get home. But it does indeed look like pins 6,7,8 are shorted together.

author: freman
author_rank: Contributor
timestamp: September 24, 2019, 04:36:49 am
content: Hey!I found that Zener (I mean, ZDP vs DP for every other diode on there, I'm going to assume Zener). It smells ok, 0.6 in one direction, out of limit in the other.I also I have no idea where CP09 is going, there's 57k of resistance between it and the rp10/cp06Excuse the crudity of my drawings, I could redo it a dozen different ways but this is basically the route I followed.I'd have to suck the chip out before I tested point to point (ie: pin 2 to positive/negative to check for a resistor bridge configuration)To my untrained eye, it has all of the basics of the FSL156RIN reference schematic with a whole lot of extras... Does anyone have any thoughts (read: corrections)?

author: freman
author_rank: Contributor
timestamp: September 25, 2019, 12:08:02 am
content: Good news everyoneOnsemi repliedQuoteWhy call it a S? Who knows. But I have 5 of them coming from RS.I'll have to check that opto and potentially have to figure out what it is to replace it but this is good.