Sanyo DP37647 LCD set

[radiotvnut]

OK, these TVs are continuing to blow holes in one local dealer's claim that they are designed to run 15-20 trouble free years in the average home.

Today, an ex-TV repairman friend asked me to look at his 2007 37" Sanyo LCD TV. He said he was watching it, the picture went out, then came back on for a second, then went out again for good. The audio is still OK. When powered up, the picture will come on for a second; then, the backlights go out. The owner did say that he re-soldered some questionable connections; but, it didn't help. I unplugged each lamp connector, one at a time, to see if that would make a difference; but, it did not. I then jumped the 4 or 5 electrolytic caps on the inverter board; which did no good. Finally, I checked for voltage at the cable connectors on the inverter board. I have B+ of 23V and there appear to be some control lines that have between 4 and 5 volts on them. I'm thinking the inverter board is the cause; but, can't rule out the chance that the main board may be turning off the inverter board. I found all the circuit boards for this model on ebay for fairly reasonable prices; but, they all appear to be untested pulls from other sets and are sold as-is. It would be just my luck to spend $70 on an inverter board just to have it arrive non-functional or not even be the problem to begin with. I don't think the owner wants to spend much on this TV. When he left it, he said, "you can either have it for yourself or try to fix it for me, whatever you'd rather do". Of course, I agreed to at least try to fix it for him.

Is there something I'm missing or does it sound like I need a new inverter board? Any suggestions would be appreciated.

[crtfool]

I repair a lot of LCD monitors, and the most common failure is the inverter board. They are designed to shut down the lamps when a short in the inverter circuitry is detected - some type of fault protection circuitry built in. What you should do is shine a very bright light on the front of the screen to see if there is actually an image on the LCD - if there is, then you definitely have an inverter problem.

[rca2000]

About 2-3 years seems to be the "trouble free" average on LCD panel sets, from what I have seen. Often MUCH less. Caps fail in many in ONE YEAR or less!!

And my 1992 32" CTC--169 was 12 years old before it's FIRST problem, almost 6 years ago--and the couple of caps and a few connections I did on it means it is STILL in my room as a daily Watcher today.

The 1985 Sony 13" trinitron I watch RTV and THIS on, was 13 years old, before it's first repair in 1998...and NONE since.

I'll keep my "old, outdated" CRT sets!!

[radiotvnut]

I have a 27" CTC169 in the living room that was being tossed by a repair shop. All it needed were some caps in the power supply to rectify an excessive B+/shutdown issue and it now probably runs 10 hours a day. The CRT is showing it's age a little; but, not that bad.

My Mother has been commenting about how good some of the new TV's look; but, I think I've convinced her that it's best to keep the old sets that I can fix rather than paying out a bunch of money in order to see someone's nasal hairs until the new TV dies a violent death in a few short years. People often laugh at me for watching such old TV's; but, I tell them that I'll have the last laugh when mine are still going while they're on their 3rd flatscreen in a 6 year period.

Tomorrow, I'll ohm meter check those ballast and see if one is shorted.

[AUdubon5425]

A few times recently I was at someone's home and they "gave the tour" of a $3000+ flat panel set with an HD video and surround sound. I mean, look, I'm not knocking it if that's what you like, I think it's great, but they always expect you to respond one of two ways: either in awe or a comparison to your own setup. There is no good way to respond when your most-viewed set for years was a 9" B&W Philco. Personally, the way most of those sets are set up and (of course) the room lights are always cut off those new sets strain my eyes after a few minutes.

[holmesuser01]

I saw a big 60+ inch Panasonic plasma set in Atlanta last weekend. The owner, an old friend, has all the latest goodies for his viewing pleasures. I was not expecting what I saw. He turned it on, and the picture was incredibly sharp allover the screen. He started the blu-ray disc, and it was an old MGM Technicolor feature. I could see the grain in the film on that screen if I got closer! We took the same disc and took it downstairs and played it on another blu-ray with a Sony Trinitron from the mid 1990's. It looked about as good as my Sony's do, but no grain.

I've stopped bad-mouthing digital.

I do bad mouth the lack of quality I'm hearing about here. You pay that kind of money for something, it should last. Both of my early '90's Sony's are still going with one minor repair on one, and a replacement kine on the other after non-stop 18 hours a day running all those years... It looks great again. I think that new sets should be built better.

I wonder if there is something even better (read expensive) coming down the pipe as I speak? Something that will render these Plasmas, and LCD's obsolete in 5-10 years?

[radiotvnut]

I'm sure the problem is with the inverter board. I ohm meter checked all 8 ballast transformers. The secondaries on 7 of them read between 5.88 and 5.95 Kohms. The last one read over 19 Kohms.

[bgadow]

I had a Toshiba given to me with this sorta problem; the lights would flash on at startup then darken; you could read the screen with a flashlight. It had some other issues that sounded like low voltage to me. (poor reception, for one) I couldn't find anything obvious so I gave it to somebody on freecycle who was going to pay to have it fixed.

[radiotvnut]

I can hold a flashlight over this one while in a dark room and see a picture as well.

I did speak to the owner and he decided just to buy a new TV rather than risk buying a board for this one and there possibly being more wrong with it or having something else go wrong in the near future. I used to never advise people to do this; but, I told him to consider buying the extended warranty with the new TV. That way, he has a little more protection should the new TV fail within the first few years.

I'll probably order the board to fix this set since I could probably unload it a lot quicker than I could a CRT set.

[Geoff Bourquin]

Almost every day I tell at least one customer that the days where we could expect something like the old Zenith or RCA console sitting in the corner running for 20+ years is over. These days, I expect the really well made sets to last for about 7 years, and the cheapies to run for a couple years (if you're lucky). I'm about to have a dump truck full of electrolytics back up to my door and let 'er go. It's not unusual at all to replace a dozen of them in one set. Some of the bad caps have decent ratings on the factory data sheets, but just don't live up to it in the real world. I've been trying to order the best quality I can, with ratings for temperature, ripple current, lifespan, and ESR at least equal to the OEM, and usually better. It just doesn't make sense to go cheap to save a few cents per capacitor. Unfortunately, the TV makers often don't see it that way.

Another wonderful device being used in todays sets is the MLCC (Multi Layer Ceramic Capacitor). 10uf at 16 or 25 volts in a ceramic surface mount device barely 1/8 inch on a side. Google it and read all about how they crack, go leaky, and destroy the rest of the electronics on a board if they get too hot, too cold, have too much solder holding them onto the board, or are picked up wrong at the factory, or if the board they live on gets bent, or if you look at one wrong and pi$$ it off!

These new sets look amazing, but there is just so much that can go wrong in them.

Back to the subject at hand, the inverter. Yep, sounds like a bad one to me.

[radiotvnut]

I saw one of those new LED TV's at Best Buy the other day and I'll admit that I was impressed at how thin it was. I probably wouldn't be impressed if I had to fix the thing. I did look on the back and didn't see any case screws. Maybe it's held together with clips or perhaps it's a sealed unit that's not designed to be opened. I know the more I see of this new technology, the more respect I have for the stuff from the past.

[radiotvnut]

OK, I dug this set back out and decided to play with it some more as I need to stimulate the economy (mine). In a dark room, I unplugged all the lamps and then plugged in one lamp at a time. This way, I've determined that all lamps are good as they all light and go off after a second when plugged in one at a time. What baffles me is that ballast whos secondary reads much higher than the others. I was not expecting the lamp that was connected to that ballast to light. Tomorrow, I'll recheck that ballast reading just to make sure.

As much as I hate these new TV's, I guess I'm going to have to learn to repair them as they are about the only ones that people will pay good money for (at least for now). Next year, they'll probably be selling 32" LCD TV's at Wal-Mart for $99.99. Then, we'll be right back where we were for the last few years of CRT set production.

[rcaman]

we do warranty work for sanyo. i say they are as good as anything being built very few problems. did you check the fuses on the inverter board. you didnt did you. post a pic of the inverter board and i can help you more. that sanyo will outlast the other cheap lcd crap out there. steve

[rcaman]

another thing the inverter will not work with a lamp unplugged it will go into shutdown. you cant check lamps that way. steve

[radiotvnut]

Originally Posted by rcaman

we do warranty work for sanyo. i say they are as good as anything being built very few problems. did you check the fuses on the inverter board. you didnt did you. post a pic of the inverter board and i can help you more. that sanyo will outlast the other cheap lcd crap out there. steve

I appreciate your help and I did check all 5 surface mounted fuses (all good). The only problem I'm finding is that one transformer with a secondary reading of 19Kohms, while the others read 6Kohms. I understand that the inverter will shut down if a lamp is unplugged; but, one thing I don't understand is that when I have the lamp plugged into the transformer with the high reading (all other lamps unplugged), it will still light up for a second (as do the others when plugged in one at a time). If that transformer is bad, I wouldn't think the lamp would light at all. Then, I think about that transformer reading 19Kohms while the others read 6Kohms. Anyway, here are some pictures of the inverter board and any help will be appreciated.

I'd like to find some broken LCD sets for cheap to practice on; but, everyone wants $75 and up for the broken ones and that's a little much to spend on something to play with. Back in the old days, I never paid over $10 for a broken CRT set and I should probably stick to that rule now. Actually, the guy that runs the TV shop had an identical Sanyo that he claimed needed an inverter board and a main board. I would have loved to have gotten it; but, he wanted $75 for it and wouldn't back down or agree to let me switch out a good transformer for my questionable one. He claimed the Mexicans would give him $75.