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Equipment Repairs => LCD TV forum => Topic started by: Davy on January 03, 2019,10:30:37
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I need a Toshiba main board for Toshiba 40BL702B, 17MB65S-3 main board.
The board is marked, 17MB65S-3.....23030449. I understand this number is the firmware version. I can get a board 23030450 - would it work? They seem to use this board in many other brands as well, Tesco Wonder Telly I guess.
Looks like the audio chipped is duff, the four 15nF caps are OK, sound at headphones but not LS, got the headphone switching voltage and the voltages are up on the chip.
If I understand right, I should get 12V between speakers and ground as one video showed, I only get 1.4V.... wonder if the chip overheated and 'kaputted' the output pair, tried pressing the chip in case of bad connections.
Dave
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Hi Davy,
Guess it depends on which screen fitted. Had a look on Ebay but both current sellers don't mention the screen but mention it might work, maybe. Gather they can't be arsed to check.
Had one in where the top edge Leds had melted the diffusers and I forgot to re-assemble the other way up so they might melt the other end - Nice pictures though. Loaned it to a chap with a 50 inch Pana plasma with download issues, he thought it great, if a bit small.
Met the 15nf cap biz several times. Gather they might check OK, but replace them anyway - Chris.
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Hi Dave,
Unless it has a weird design, there should be no DC on speakers as far as I know. It's a recipe for burning out voice coils. Suspect the audio output chip
is duff, letting DC through to the speakers.
Bruce
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Hi Bruce,
Have a set myself where the speakers are DC above ground. Not an issue unless you ground the speakers. Guess something to do with bridge output - Chris.
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Saw a video where it said 12V I think it was between speaker and ground, there's no DC blocker in sight for the speakers and a single supply is used on the NTP8030, speakers are not grounded anyway.... all I can muster is 1.4V.
I'm waiting for a supply of SMD caps, could be breaking down under voltage as Chris said... odd both channels should suffer.
I don't know what the sound is like, might be better get a sound bar and use that, bet it sounds like listening to HI-FI on a pair of them Hi z 'brain clamps with a coil and a diaphragm made from a soup can, Sargent Browns where they?
Must get set up for BGA work.
Dave
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Hi Davy,
As the two O/P chips are microscopic SMD - Wouldn't care try change any. Those four caps are bad enough as 1mm x 0.25mm - Bit small.
Recall got a bag of 100 and most flew away. Don't know what they die from, just change 'em, seems to work if you don't duff up the print.
Guess SG Brown the biz though suspect the diaphragm dubious for Hi-Fi - Bit like the Carbon granules on old BT phones.
Recall way back used two Heinz beans cans and a length of taught string.
Best of luck with your BGA work - Chris.
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Hi Turnip, Happy New Year to all, before I forget.
1mm x 0.25mm you say that would be either 0402 or 0603 size, thought they looked to be about 0805/1206 size, not taken em' out yet so haven't measured them, at moment the telly is boxed up.
I keep eyeing a Quick Hot air station, here's a review.
https://www.eevblog.com/2018/02/20/eevblog-1058-quick-861dw-hot-air-rework-station-review/ (https://www.eevblog.com/2018/02/20/eevblog-1058-quick-861dw-hot-air-rework-station-review/).... I'm very tempted.
I could 'try' and lob some Mylar caps in, they should do the same job, it's only a snubber.... the speakers do look crap to me so not expecting much here.
Dave
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Hi Davy,
Use an Aoyue Int 853 myself at around 80 Quid - Cheap and cheerful, plus a blast of heat from above. As to the caps, guess I bought the small ones, sort'a 100 for a quid from China.
Had the thought to use soldering tweezers, but the cheap Chinese ones were crap - The ends didn't meet and they glowed Red within minutes. Sorted quite a few with solder mop and a single iron, mind you, had some print issues, but not yet a failure.
Would have used the rework station - Great for T/con issues - but that Vestel board is closely packed in that area - Chris.
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Hi Turnip, Happy New Year to all, before I forget.
1mm x 0.25mm you say that would be either 0402 or 0603 size, thought they looked to be about 0805/1206 size, not taken em' out yet so haven't measured them, at moment the telly is boxed up.
I keep eyeing a Quick Hot air station, here's a review.
https://www.eevblog.com/2018/02/20/eevblog-1058-quick-861dw-hot-air-rework-station-review/ (https://www.eevblog.com/2018/02/20/eevblog-1058-quick-861dw-hot-air-rework-station-review/).... I'm very tempted.
I could 'try' and lob some Mylar caps in, they should do the same job, it's only a snubber.... the speakers do look crap to me so not expecting much here.
Dave
Hi Davy,
........ Had the thought to use soldering tweezers, but the cheap Chinese ones were crap - The ends didn't meet and they glowed Red within minutes.
I was looking at tweezers myself and thought, two soldering irons will do the job... I seem do the job with my Ersa i-con 1 with the right tip, but once removed the components a 'goner' usually due to heat.
That's reason I'm not going for a cheapo hot air station, so much crap knocking around.... nearly bought an Atten soldering station but one review showed only three wires to the iron part. ground and power feed. The way it regulated was it monitored the element current through a low value resistance, RS Components tech department actually confirmed this to me.... so many complaints of poor regulation due to tip cooling down on contact.... guess that could cause 'track ripping' when using de-soldering braid.... the Ersa i-con iron looks ridiculous with a 10mm tip...!
The very reason if I get anything like this I prefer to buy one and once only, meaning buy a good one and have done, been 'had' before with junk.
Would I be right in thinking you can't control the heating area with a hot plate? A cooker element with thyristor/triac control or even a variac with a ceramic plate over the element.... a couple of 100W metal clad resistors even should work, should be alright for egg and bacon butties too.
Dave
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hi have you reset back to first time installation in menu have read few people with no sound have cured by this
regards
astracat
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Hi astracat.
Yes I tried all that, tried the service menu as well to no joy.
Dave
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Hi Davy,
A two soldering iron man myself as seems the cheapest option, and if nifty can lift out a component no problem. Admit my main iron is an R/S four wire 48 watt jobby from the 70's with a primitive 24v soldering station.
Note that 'Hakko' does a modern temperature controlled equivalent for under a fiver, not needing a solder station, as its all in the handle.
Nevertheless bought a Chinese control panel, sorted a box and transformer, making a cheap solder station. Only issue being that Chinese temperature controlled elements have several different formats - Eventually sorted - Chris.
PS - Had a look at hotplates as domestic are the cheapest. Trouble is, they're mostly round for saucepans, where we are mostly linear for the odd chip. Thought try sort something as you suggested.
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Anyone tried the cooker or microwave combi?
When 'er indoors goes shopping I might try the cooker for fun, got some some scrap boards, nowt like frying a Tesco Wonder Telly board.... fried chips here we come!
Dave
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Hi Davy,
Today cooked an LG SSB for the second time, as first time it suggested 'Life's Good' but couldn't move on due to BGA issues.
Noted on Ebay that SSB boards for the set are unavailable as they all go duff due to LG soldering issues.
Success - Don't try a Vestel board as it doesn't work, doesn't work on Pana and Sony either, tried 'em - Chris.
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Good work that is... wonder what does LG do different?
Well, I've had no luck, convinced it's the chip in this Panny, changed the 15nF's and still same, looks like the output pair in the chip is kaput, I'm getting the headphone switching voltage so that isn't the problem.
Dave
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Hi Davy,
Recall had a Vestel with no speaker sound. Chap had an elderly neighbour who kept banging on the wall so he used headphones in a rather energetic manner duffing up the socket - No speaker sound. Guess in your case something different as you note switching - Chris.
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Yep, headphone got it's own amplifier in the chip and the switching voltage mutes the speakers.... I've checked the contacts as well on the headphone jack and all voltages seem to agree on the chip data sheet, checked from chip to speakers.
Half the time the Tesco Wonder Telly's sound are crap anyway, reckon a sound bar is the way to go or at least a audio feed to an amplifier, analogue audio is OK on the scarts.
Dave
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Hi Davy,
'Tesco' tellies have recently got even worse, as they seem not to use Vestel as China is cheaper, and may work 'till the guarantee expires.
On the up-side, just had a couple of 32 LG where the sound is rather good but the screen Leds die like flies. Not an issue with Vestel small screen sets, not yet had a duff one smaller than 32 inch using a Vestel panel and LG Leds.
Good luck changing the chip, should be a doddle as has pins - Chris.