Fixing a HDTV after a Power Surge - Page 1
Forum section: electronics / beginners

author: Falcon69
author_rank: Super Contributor
timestamp: March 04, 2014, 05:56:45 am
content: Okay,Here's the problem.The TV is old, like maybe 6 or 7 years old. It is a 65" Mitsubishi Medallion (model number WS-65611) series with the added HDTV box. There was a power outage the other day, and since then, the TV won;t turn back on. I tried doing a search on how to fix this, but all I can find is people mentioning the DM (digital Module Board) and replacing four 16v 1000uf capacitors on it. But, I've searched all inside and cannot find this board.Anyone have experience in fixing this TV and/or the power surge problem?I have checked the fuses (the main fuse and the Pico Fuses located all over the board) and they are all fine.The green LED on the front of the TV flashes steadily, but the TV will not do anything else.I hate to have to tell my brother that he needs to take it to a repair shop or throw it away (not an option, as the TV was $3200 new). I'm pretty sure I can fix it with my soldering skills, but my trouble shooting skills are sub par.Also, he notified me that the blue color bulb is starting to go out. I had also read that when the onboard protection circuit protects the TV from a power surge, after power is restored, the TV goes through a self diagnostic and if it senses any bulbs out, it will not turn the TV on. If this is the case, and not the capacitors as others have said, is there a way to bypass this and turn the TV back on?Thanks in Advance for any help.Jason

author: Falcon69
author_rank: Super Contributor
timestamp: March 04, 2014, 06:48:26 am
content: Okay, found the DM board. It's located inside the HDTV box in located on the left rear of the cabinet. The only one I did not take apart.There is 7 capacitors on there, all 16volt 85°c and 1000uF. Can I replace them with something better? I am limited to 10mm diameter case and 5mm lead spacing. But, I may have alittle extra room in height.Maybe 25 or 35 volt? 105°c? Will changing to those values help them last longer?

author: Barryg41
author_rank: Contributor
timestamp: March 04, 2014, 07:03:11 am
content: Just in case you needed the schematics and service manaul here's a link to them:http://elektrotanya.com/?q=showresult&what=WS-65611&kategoria=&kat2=all

author: Falcon69
author_rank: Super Contributor
timestamp: March 04, 2014, 07:09:20 am
content: Wow, thank you Barryg41Also, I just read that in some cases, after a power surge, the convergence IC #STK393-110 may need to be replaced if the picture quality is bowed. Is this chip available under a different number? I put that number into Mouser, and nothing comes up. The ones on eBay are all from China.

author: Skimask
author_rank: Super Contributor
timestamp: March 04, 2014, 07:46:09 am
content: There's a lot of STK393-110 substitutes. Some better, some not so much.Google is your friend.As far as the eBay/China ones, I've used various STKxxx-xxx types in the past, maybe about a dozen TV's in the past 6+ years. No recurring problems so far.

author: Stonent
author_rank: Super Contributor
timestamp: March 04, 2014, 02:03:04 pm
content: Do you smell any evidence of magic smoke anywhere?

author: electronics man
author_rank: Frequent Contributor
timestamp: March 04, 2014, 04:54:22 pm
content: do you have an esr meter

author: Falcon69
author_rank: Super Contributor
timestamp: March 04, 2014, 05:18:52 pm
content: Quote from: Stonent on March 04, 2014, 02:03:04 pmit's got an inch of dust in there. i don't smell anything but that. lolQuote from: electronics man on March 04, 2014, 04:54:22 pmnope, just a multimeter.I'm goin back over there today to take another look and pull the dm board out to see if the caps are bulging.It will cost $300 for a repair guy to fix it, and he will want to replace the DM board at another $1000. If I can fix it for $20 worth of caps, that would be great!

author: Falcon69
author_rank: Super Contributor
timestamp: March 05, 2014, 04:54:18 am
content: Okay,I had a chance to get back over to my brothers and take the TV apart and I found that DM board, and sure enough, seven 16volt 1000uf capacitors are on it. However, I don't see any damage, no bulging, not exploding, and no discoloring of the circuit board solder joints or traces.Is it possible that the power surge can still make these caps go bad, even though visually there is no sign of damage?Regardless, I ordered them from Mouser. In a few days, I'll try putting them in and see if the TV fires up.

author: Skimask
author_rank: Super Contributor
timestamp: March 05, 2014, 05:13:19 am
content: I seem to remember something about the blinking light on startup...The exact problem escapes me but it was something to do with the HV being too high.All it took to fix it was to take off the front panel, turn the HV coil down just a hair (and I mean just a hair, barely had to bump the pot). Fired it up and it worked. So whatever it was, that HV being too high, must've been just barely too high.I'll see if I can dig that up... It may or may not apply. It was a Sony RP TV, 60" model, a few years ago as well. But seeing as how a lot of these RPTV's use the same chassis and the same PCBs with minor mod's here and there, it just might apply.

author: Falcon69
author_rank: Super Contributor
timestamp: March 05, 2014, 06:42:53 am
content: I'd appreciate that, where is the HV coil located? I took the front panel off, but there's not much to it, just some tactile switches, rca audio/video input, and an led. There's really no electronics on it.

author: HalfSpace
author_rank: Regular Contributor
timestamp: March 05, 2014, 09:29:43 pm
content: Hi Falcon69,Have you tried the "LED Indicator Diagnostics" on page 30 of the service manual? This will indicate error codes or maybe the malfunction.HalfSpace

author: Falcon69
author_rank: Super Contributor
timestamp: March 05, 2014, 10:04:04 pm
content: Yup,Fast Blink (doesn't stop) After AC is applied TV ?PC is running, but DM failed to boot upThat is why I am hoping that replacing those capacitors will solve the problem. I will find out in a few days when I receive the caps and install them. *keeps fingers crossed*.

author: EEVPiobee
author_rank: Contributor
timestamp: March 06, 2014, 12:20:55 am
content: Did you have a blown fuse??I may suggest to check for TVS (transient voltage suppressors) as well... I had the same problem as you say... These will protect you TV from going out in flames when lightning strikes into it, but may also come shorted afterwards...These are Zener diodes rated to a certain voltage (and certain wattage) that sink any excess voltage to ground... Once they sacrified themselves to protect you, your TV (or anything that has it) becomes unusable..If you have a shorted one, you could simply remove it and if that was what made your TV stay off, it should turn on without it (but I don't recommend having any safety feature removed!)

author: Falcon69
author_rank: Super Contributor
timestamp: March 06, 2014, 12:39:51 am
content: All the fuses check out. I didn't see any zeners that were fried. I will try and locate those TVS ones and see what I measure with the multimeter.

author: peter.mitchell
author_rank: Super Contributor
timestamp: March 08, 2014, 04:52:24 pm
content: CAREFULLY check the voltage rails, i often see little sot-89 and sot-223 regulators bite the dust.

author: Falcon69
author_rank: Super Contributor
timestamp: March 18, 2014, 07:56:19 pm
content: Caps fixed the problem! TV is turned back on.The blue color is not bowed on the screen, as I was told, so the convergence IS chip is not the problem. The Blue color is gone completely. So, looks like a new bulb is needed. Anyone know where to get one of these? The tv is 10 years old, and It doesn;t seem to be available anywhere I can find.Jason