Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: OldLes on February 02, 2013,08:04:14
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Yesterday, a visit to the local amenity site yielded this very tidy looking set. It even had a helpful note suggesting "faulty inverter board, ideal for spares".
At switch on, brief green LED, 9 orange LED flashes (booting up period?) and a green LED. Screen "Wakes up", and an OSD message suggests CVCS-1 input (I think), followed by shutdown.
When I looked inside, I saw evidence of some overheating at the two connection points of the inverter board to the top two of 18 lamps.
I have yet to see if I can find any component faults, but if none, can I simply leave the top two lamps disconnected for testing purposes.
I am inclined to remove the two plastic clip connection holders, and wire these two lamps directly.
I don't see any superficial evidence of damage to the ends of the lamps compared with the ones lower down.
Any comments on this procedure? (If successful, I will be keeping this set for me).
OldLes.
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Do you mean the white clips that go into the screen? If so, just replace them.
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Mark, the little white clips had overheated, but a repair attempt had been made previously, with an extra thin sliver of copper soldered onto the inverter board's contact point. However, in its original overheat, the temper was obviously lost by the clip, and it was obviously unsuccessful.
I checked all the fuses, compared resistance readings of all the bigger semicons, but found nothing amiss.
So I dismembered the two plastic clips, bent the back part and crimped a short length of wire to each one. I then removed all the overheated connector area of the pcb, and soldered the wires directly.
Connected back up, but still the same.
There was one page from a service note in the back of the set, which says that if there is a fault on the inverter, after five start up attempts, it will be blocked. Maybe this has happened.
I will search for a service manual (or does anybody here have one?) and see what to try next.
I don't have a remote, so not sure if I should buy one. I don't want to throw good money after no money, but it may be necessary.
Les.
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Most likely a faulty lamp. To check,remove the front plastic cabinet section, remove the LCD panel and diffusion sheets under it, to expose the lamp cavity. Best disconnect the Flexis from the T-Con to the panel. Dont need them for this test and you dont want to tear them. At this stage the set is operational but has no LCD panel.Lay the set on it's back, switch it on and wait for the lamps to switch on briefly. After repeat switch-ons you should be able to identify any lamps that do not ignite or light with a pinkish glow. Even 1 lamp below par will trigger the protection on these. Nor can you run them with 2 lamps disconnected.
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You had to do a lamp error reset,
The best way is to change all the 18
lampsocket, becourse sooner or later some of the others
will do a bad connection with the inverterboard.
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I have plenty of lamps and some connectors for this set if needed, they do suffer from lamp failure probably due to the white clips failing resulting in intermitent connections, I have the manual and all the service updates for modified connectors I'll put it in the downloads section.
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It won't let me upload it, if you need it I can email it to you.
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Clark97, I now have the manual (earlier messager loaded it) but any updates will be useful. I will PM you with my email address.
I am satisfied that my "bodge" has given me 18 good connections, so I need to see next if any of my tubes are faulty. If so, I would be happy to receive some.
I have some tubes from a 26" which came my way last week, a "Vistron" with cracked screen, so probaly all good. Can I temporarily hang some of these externally to test things out?
Do you have the remote I could buy or borrow?
OldLes.
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Clark97, I have only just opened the document which Kilroys uploaded, and realised it is only pages 1-5 of chapter 3.
So, "yes please, may I have the complete manual".
I have just sent you a PM with my email address.
OldLes.
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Well, after about 2 hours in Terminal (Ubuntu 10.04) I finally managed to "Un-Rar" the manual. I then went further and reorganised it into one complete pdf. Now I just need to study it a while before I get back to the set itself. If I can fix it, it will take pride of place in the living room, and the existing one will be up on the bedroom wall to keep SWMBO happy.
Thanks Clark97.
OldLes.
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Right, some progress. I have a Sharp remote which will switch it on and off, so it may do everything when I get it running properly.
So, darkened room, and switch on. After normal boot up, the screen illumination showed that three of the CCFLs were not firing up.
So, that is my next step.
Clark97, I will be sending you a PM.
Les.
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At the time of the last message, I had established that three of the CCFLs did not seem to be lighting up during the 2 to 3 second (test?) period before the set shut down.
I came across a Samsung 41" set with cracked screen, but its backlighting was OK, so I managed to rescue some tubes. I dismantled the screen assembly, and removed the three previously concluded as faulty tubes. The Samsung tubes were a little shorter, but I soldered on a short extension and made some (sort of tie wrap) connections. Reassembled everything and tried again. This time, it appeared that there were FOUR faulty tubes, none of which were the replacement ones!!!!
I have today tested the originally condemned three tubes, and they all work OK on the new tester.
What next? Hmm, maybe ------
Les
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Your final statement may not be so strange, Les. I've removed non-operating ccfls from Sharps, then at a later date, installed them in another Sharp to discover that they work. Go figure. I prefer to operate them with the ccfl cavity exposed (no panel) so I can see exactly what's going on. Good luck with it.
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Hi folks,
Had one in today with a couple of those edge connectors burned out.
Noticed ChasHyde do them for 3.80 plus but (as there are 18) thought to try hard wire the duff ones first.
Problem was - that on re-fitting the inverter panel, several of the other connectors didn't make contact.
Had that sinking feeling so think to hard wire the lot - Only problem is - those springy clips won't solder, neither will the tube wire ends.
Think to wrap wire under the clips, and do a 18 tube hard wire job.
Recall edge connectors with single sided print always crap - Speccy - Pye tellies of the 70's - Chris.
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Turnip, my set is still awaiting further attempts to fix. In fact today we decided that that was on the list for next Monday afternoon, when my pal arrives and we play at "digital stuff" with a low success rate!
We thought we had this fixed, after hard wiring the two burned out ones, but whilst it would attempt a start up, we found DIFFERENT lamps were now not lighting. I don't think we tested them with the new tester, and this is our next move. Good luck, and if you win, PLEASE report back!!
Les.
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Hi Les,
Got that Chinese tube checker, and all tubes tested OK (even that one I broke and replaced with a 40 inch with long wires) before I reassembled the screen.
Hard wired every tube to those convenient inverter feedback caps - wrapped one end around the tube clips, as wouldn't solder, then glued to keep things in place.
Didn't manage break anything on reassembly - tedius job with all those screen screws.
Thought to leave water based glue to set for some days before I try fire up.
Cowardice maybe, but genuine Sharp gives me that sinking feeling.
Later - glue set - fired up, did a total reset - OK - whew - Chris
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I have never had a bad tube on the 42DH77 sets.
Well one, when I was loosen the clip from the tube and was in a hurry.
LV-347 describe the most common error, guessing it's because spring is
soft from the heat and makes poor contact.
If the set takes a long time to start, the clips look ok,
no burnt mark on the inverter, it could be LV-441.
Never loosen the inverter if you are not sure its the clips
or you will have problems with the contact.
I have had both, but most common the clips.
After changing the clips you had to clear the lamp errors.
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Hi Kilroys,
Like you never had a duff tube (before I broke one) but those inverter contacts are total rubbish. On replacing the inverter panel, several didn't make contact.
Wouldn't suggest new spares as they're expensive and no better than the original horrid design.
Next time won't bother dismantle the screen, just snip plastic over inverter connectors and hard wire all 18 tubes to the appropriate side of the inverter feedback caps.
Prob is - edge connectors contacts won't solder, but a good fine wire wrap with adhesive might be as good as it can get.
Done one, fingers crossed - Chris.
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Hi guys just repaired two of these sets and its not the lamps it's the crappy clips that make a bad connection and arc making a hole on the inverter board , just turn down your iron so the solder doesn't melt to liquid and solder over the inverter holes take the clips and run the iron over the the connecting point of the clips bend them up if needed reset the lamp error in the service menu and vola set fixed hope this helps
Alwyn :13:
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Hi Alwyn,
You're right with the inverter board trouble - Prob is, clips don't solder - still suspect a hard-wire jobby is the best biz, but yet only done one - Voila - Chris.
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I see it is March since I last played with this set (LC-42DH77E). In spite of bodge repairs I never got beyond briefly seeing which lamps NO LONGER light.
Having read the "Shuts_down_lamp_error" pdf, next move is to put a S/C on C7558. Different location of C7558 on this set from that shown in the document. S/C link fitted, switch on set. Flashing red LED, unlike previous condition. Have they changed the "prevent shut down capacitor"? Is it a different component number in this set? Beautiful looking set, would be perfect for my living room, but I can see it being consigned back to scrap. Any comments?
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Maybe the last message is not very clear. I am attaching the Sharp bulletin concerning shorting C7558, which is shown on the second page. C7558 on my set is much nearer to the IC than that shown.
Of course if I had a circuit of the inverter, it could make more sense, but that seems to be absent from most circuits, so you are left in the dark.
Any suggestions welcomed.
Les.
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Hi Old Les,
General opinion is that the tubes are usually OK on this model but edge connectors are suspect, as can be seen by the burn marks on those plastic connectors and the burned holes in the inverter panel.
Just hard wire and do a reset - nice telly - All the best - Old Chris.
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Hi Turnip (sorry, Old Chris) and Kilroys. Decision already made on next step before reading your message Chris. This afternoon, another Monday, so with my pal we hauled it back onto the kitchen table. Inverter board out, up to electronics room, and remove last week's incorrect short. Of course the SM cap came out as well, so it took a good half hour before that was back to standard. After locating C7561, I managed to solder on a single strand from a thin wire to short it out. Again, quite a time consuming task. I worked under my 10 Xs Stereo microscope, with the finest tip iron in my armoury. Glasses and Ledu for getting things ready, glasses off and microscope to do the job. I think back 25 to 30 years when I routinely replaced up to 10 diodes on some earlier Grundig CTVs, and about 5 little black 0.1 caps on their Tuner-IF boards. It would not be profitable today with these "smaller than ever" components.
But what happened? We failed to get to the "K" screen, but this time we did see ATV 54, suggesting it had been last used on analogue "commercial", before it went to standby. And about half to one third of the CCFLs not lit!
So, it is to be the front off next time, and EVERY CCFL will be re-tested, and then individually hard wired Chris's way. I think the best method will be to use enamelled copper, well scraped, and fitted in Thorn's "tie wrap" mode.
Believe it or not, I am optimistic that sometime in the near future, I will have this set in my living room. I bought my current LCD, an EVOTEL, just over three years ago (my first new set since my 22" NordMende back in 1970, and only £15 more expensive!!!), so I guess that will be packing in before to long.
Les.
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Hi Young Les,
Took the front off meself feeling tubes were the problem, well, it's a Sharp, and we know 'em.
Naturally they were OK of course. But go for it, I did, but was freaked with the possibilty of disaster.
Mine was a customer jobby, and the inverter hard wire did the job - Not a 'kind word' or 'refund' since.
Made the needy pound though - Old Chris.
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A couple of weeks ago, we had the front off, and re-checked all lamps with the Chi-tester. All OK. Rechecked the three tubes swopped out months ago, all seemed OK, so decided to re-fit them rather than leave the three shorter ones.
I then carefully wrapped each tube clip with 0.6mm silver plated copper wire (as used by my Ex for jewelry making) and then crimped it tightly.
Soldered a short flexible lead to each pad on the inverter board.
Carefully reassembled, this time with the soldered link on the correct (I think) capacitor, C7561.
Tried switching on mains whilst holding input and vol -. Flashing amber, then continuous green, and eventually about 1 to 2 seconds of lit tubes. Spotted UTV Ch 52 on RHS, but no sign of the infamous "K". Repeated attempts seemed to be accompanied by the set cycling thro' inputs each time (DTV, the "No Radio Channels) etc.
Tried various combinations of buttons, but never a sign of the "K".
I am moving towards the decision to return it to the amenity site, but hate the idea after all this time, with such a beautiful looking set.
Les.
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You had to use the power cord when switching
off and on the set to access adjustment menu, not the power button.
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OldLes, that CCFL tester, is that the one with a longish probe, an earth clip and red/green LEDS - only have a vague memory of one that a friend of mine bought online. First tv he checked was a Samsung. The tester read all CCFLs as good. I was somewhat dubious so I later got him to crack the panel open. What do you know, 2 tubes were out. Personally I don't trust them as they test the tubes in an inert state and it seems they tell porkies.
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Kilroys, Yes, tried both physically plugging in, as well as the lazier route of using mains switch at 13A socket.
We could switch off and back on again with the set's on button, seeing again briefly the Ch No or DTV etc, followed by lamps off again. Using the mains switch, at no time did we see the "K" giving use access to "stuff".
Les.
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Hi Young Les,
Think mentioned B4 that all those inverter to screen connectors are suspect - suggest hard wire the lot - saves time, and did the job.
Did mine only in thin plastic covered copper -
Copper is getting expensive, esp for plumbing improvements - Called in at a supplier for some yards(metres) of 14mm (half inch) - horrid - pricewise.
Sharp Inverter/Screen hard wire requires just a few Centi-whatsits, if you're nifty with the side-cutters.
Not so nifty myself, and kept snipping the ends off - but eventual success - Old Chris.
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Turnip, I am quite satisfied with the connections. The originals fail where they clip onto the board, and it seems even good ones fail next time you refit them. I cut the top off the clips, "wire wrapped" them with the silver plated copper wire, crimped tight and left a tail. Fitted them onto CCFLs with tails sticking up.
Soldered THIN flexible leads to every solder pad on the PCB, refitted the PCB, snipped my tails at an appropriate length, the soldered the flex tails to the rigid tails. As a repair, I regard that part as a 100% fix that you must NOT do for a customer. (H&S Gestapo)
I have been thinking about it today. I definitely shorted out the correct cap (second time around), but it refuses to display the "K" service menu. Why on earth do they not give the circuit of the inverter board, when EVERYTHING else is shown? I may try to trace it to see if I can figure it out. Either that, or back to the tip with deep regrets!
Les.
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Old Les,
A couple of bulletins for you to peruse. Para 7 on page 2 of Bulletin CTV236R looks interesting.
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Back to basic
Cut or unsolder the wire that shorted c7561.
It was useless, c7561 goes to over voltage protections.
My mistake, looked at the 37dh77 inverter.
Look at the CP signal at pin 3 in the block diagram. Can perhaps be something to be shorted
What happend when you are holding down the power button,
and plug in the AC power cord to turn on the power.
If you see the upgrade screen, try then to make a
upgrade.
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Kilroys, thanks for this. It had occurred to me that there must be something wrong with that link, or the possibility that the earlier link I did had caused problems.
Hopefully may get to look at it Monday, but it MAY have to wait until after Xmas. (I hope to have a joiner fitting a wardrobe, and a roofer doing some roof work).
Can I suggest you edit your earlier advice re. C7561, as anybody reading this from scratch could get it wrong like me.
I was NOT wanting to scrap this set, but was getting to the stage where is was next move. Hopefully the study of the diagram and a bit of googling chips may help get a solution.
Les.
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Hi, Old Les,
Only had the one, and after doing the check tube biz, where none were faulty, suspected main prob was those edge conectors, so hard wired the lot.
Set not back yet, guess poss there are now other probs, but not yet met 'em.
Keep us on board with thoughts - Chris.