Help repair power board - Page 1
Forum section: electronics / repair

author: gointern
author_rank: Newbie
timestamp: February 22, 2018, 10:38:26 pm
content: Hey,Anybody willing to help me out with TV receiver power board repair? So you know I am beginner in electronics.The short story... one day I smelt burning when I opened the box I saw that the power board has burn marks. I already replaced capacitor.The problem is I cannot track down components by their product numbers or board by its number.Is it possible to even fix it? or its just better to get a new one... I would like to fix it. It would be great practice.Image gallery:https://imgur.com/a/winTe

author: keymaster
author_rank: Regular Contributor
timestamp: February 22, 2018, 11:04:18 pm
content: Quote from: gointern on February 22, 2018, 10:38:26 pmThe 4 black components are diodes and they are all the same and form a full bridge rectifier. The problem is that the board is burned and possible now has became contractive. You will need to cut the black part of the board and reconstruct the missing peace in the air or in a small new peace of board. You do not need to use 4 diodes , you can use full bridge rectifier module .

author: Samogon
author_rank: Frequent Contributor
timestamp: February 22, 2018, 11:09:53 pm
content: Burnt are rectifier diodes. Possible that one or two got short and burnt PCB underneath. According to the fuse rating 250V 2A, i would say any general use diode with 400V ~2A rating.But main concern is charred PCB, you have to cut off this part and restore before you go and install new diodes.Also it is possible that surrounding components suffered thermal stress.

author: Armadillo
author_rank: Super Contributor
timestamp: February 23, 2018, 07:29:16 am
content: This is the simplest of TV receiver power board I have seen with singular output voltage.I think it would be cheaper and easier to find a replacement board than repairing it.

author: capt bullshot
author_rank: Super Contributor
timestamp: February 23, 2018, 08:25:16 am
content: This board looks well cooked- due to overheating caused by el cheapo design. IMO the best way to deal with it is to throw it away.Most probably, there's more to replace than just the primary rectifier diodes. E.g., the electrolytics look cooked also.The good thing is: It looks really simple, just a single output voltage. If you can find out that voltage rating (maybe it's printed somewhere on this or another board), you can replace it by a simple power brick of appropriate rating (looks like a 40W or 60W supply should be enough). You could even try to power up the TV with a adjustable lab supply.

author: frantisek
author_rank: Regular Contributor
timestamp: February 23, 2018, 11:28:23 am
content: In any case, check the diodes and replace the electrolytes. C 11 it is visible behind it ..

author: ChrisLX200
author_rank: Unknown
timestamp: February 23, 2018, 12:57:30 pm
content: Need to know the output voltage, but one of these may be adapted as a cheap replacement:https://www.amazon.co.uk/Output-Supply-Universal-Adaptor-Display/dp/B00HY3AA3S/ref=sr_1_90?ie=UTF8&qid=1519390398&sr=8-90&keywords=DROKhttps://www.amazon.co.uk/Switching-Supply-100-370V-85-265V-Isolated/dp/B00NXKHZ7K/ref=sr_1_96?ie=UTF8&qid=1519390398&sr=8-96&keywords=DROK

author: gointern
author_rank: Newbie
timestamp: February 23, 2018, 07:13:53 pm
content: An update. I have replace diodes and capacitor but it does not seem to be working.So I am thinking going with DROK AC/DC switching power supply module as ChrisLX200 suggested. I just don't know how would I figure out what goes over the 4 cables going from power supply to the main board. Above the cable connection I can see it says +12v.Which points on the board should I probe to find out where the power stops going?

author: Chris56000
author_rank: Frequent Contributor
timestamp: February 25, 2018, 01:12:07 pm
content: Hi!I've had a look at your Image Gallery and my recommendation is to buy the one in the second link:–https://www.amazon.co.uk/Switching-Supply-100-370V-85-265V-Isolated/dp/B00NXKHZ7K/ref=sr_1_96?ie=UTF8&qid=1519390398&sr=8-96&keywords=DROK. .it is a slightly better quality PCB than the first and is much more suited to fitting in your TV as the two–pin white mains connector plug from your old burnt board can be resoldered direct on to the new PCB from Amazon.I would also order some of these:–https://m.ebay.co.uk/itm/30Pcs-2-Way-2P-PCB-Mount-Screw-Terminal-Block-Connector-5-08mm-Pitch-Blue-H-J1C4/322930084764?epid=2074444930&hash=item4b30220b9c:g:u6kAAOSwZlZaKwJT. .for soldering to the output side (V1 and V2 marked connections), as it's then very easy to cut off the old PSU connector plug, strip the ends of the leads and screw them in to the terminal blocks you've fitted to the Amazon power supply PCB.Unfortunately the original burnt PCB doesn't have the voltage points marked on it, so you will have to look for +5V and +12V markings on the rest of the TV PCBs themselves – if you can't find any markings, please post a model number and as many pictures of the remainder of the set as you can and we'll advise how to wire the Amazon psu in for you!Chris Williams

author: SeanB
author_rank: Super Contributor
timestamp: February 25, 2018, 04:48:25 pm
content: The original well cooked power supply is only a single 12V 2A power supply, the leads on the power connector are in parallel to supply the 2A. Likely any power supply that gives 2A will work there, and the original one likely will work again with the input fuse ( black heat shrinked item marked F1), the 4 diodes and the small electrolytic capacitor C2, C3 and the bulging capacitors on the output side, likely C13, being replaced.

author: gointern
author_rank: Newbie
timestamp: March 09, 2018, 11:10:55 pm
content: Thanks everybody for the help!!!I probably went for the easiest route. Replaced 4 diodes, 2 capacitors, and a fuse. It has been working for over a week now!