Mulja tv repair portal
Equipment Repairs => LCD TV forum => Topic started by: scooby-doo on December 05, 2011,18:04:49
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hi
Seen this problem a couple of times and thught Id ask?
With this inverter board I315b1-16a(quite a common one, Ive attached a picture)
I have one that all the caps are ok, transformers all read near on the same, fuses ok..but the set still does the flash for 1 second then go out..(I know it is the inverter as tested with working one).
Where the hell is the fault on these boards???
Surely there is a repair kit looming on this one Andy??
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had a few of the cmo inv having duff mosfet IC's the wee 4 legged ones spaced along the board
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Cheers Jimca
Learning Curve question...Can these be tested in circuit...and ermmm what am i looking for sc/oc etc etc
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you cant really test a mosfet in circuit with a multi meter to see if its switchin properly etc but you can do a wee go/no go with your meter . To get the exact wiring of the chip used you'd need to look it up[ but many are 4 legs on one side joined together and the other side going into the pcb. Using a simple comparison check from the shorted together side to each leg on the other side in turn you can generally spot if one is different/open or short when compared to the others it isnt a full safe but it is a quick check and i've found a few that way . The other thing to keep an eye out for is dry joints on the connections of the trannies and the tube connectors.
http://www.lcdtvrepair.us/articles/How_to_repair_an_LCD_inverter--18 have a look at that when you've time
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Cheers Jimca
Just tested the fets and you were spot on mate...One was giving me some dodgey readings out of circuit compared to the other 2 I tested...replaced with one from an old board and no more shutting down.
Thanks again
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no worries good you got it going ! you must have caught me in one of those rare lucid moments ! incidentally its Jim, the ca bits just cause i needed the number of letters to register !
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Cheers Jim...will remember for next time
Just another quick query the link you put up for lcdtvrepairs.us
Was just browsing the site and came across the desoldering techniques page
was looking at the video for the product called "ChipQuik"....have you used this/or has anybody to that matter...seen the product on Ebay and bloody hell its dam expensive for what looks like flux and a type of solder that stays molten for an extended period of time
http://www.lcdtvrepair.us/articles/SMD_Soldering--4
Is there any alternatives to this..it does look quite a good option for taking those ic's off board
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Hi S/D,
Interesting video - never thought of using LMP solder to avoid pre-heating. Wonder what it is - looks like plumbers hi-lead but melts at a lower temperature - Wood's metal maybe ? Found using normal solder and 'mop' tend to loose the odd track at times - Chris.
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Well guys to be honest I don't use any of those products I simply squirt a little liquid flux round the legs gently heat with an electric paint stripping gun set to heat 1 ( 350 c ) then when the solder starts to run simply lift off the IC with a pair of tweezers. To fit the new, reverse... a spot of liquid flux hold the chip with the tweezers heat till the solder runs bobs your uncle! Used this method very successfully for years its cheap, its effective and I get to air my spurs and 10 gallon hat while doing it !!!
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Chipquik is great for.lifting the component & not the track, not quite as good as a heat gun in my opinion.
You solder it on & the component will lift off the track, but will stay lifted for about 15 seconds, giving you enough time to remove it then clean the board. It is a form of another metal, not sure if its woods metal, seem to think its fields metal, if you've never used it give it a go. A small pack of it would be enough to do around ( for example ) 50 sm eeproms. Ice never understood why this much is sold with only 5 wipes. That fact alone put me off buying it for years. If you break it down £ for £ its good value.
Regards
Andy
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Cheers Jim that sure beats my smd removal tool
(http://www.2manytoyz.com/hardware/lugs/iron.jpg)
But with the heat gun I always worry about melting the ic....I have tried it, got my temp probe under the ic and crap a brick when it reaches a high temp without movement...then back off....I dont think the bubblling effect in the pcb and ic is good look. Will have to give it another bash though
Do you stock the ChipQuik Andy?
It does seem dam expensive for desolder/rework kit...solder/flux/wick/wipes...from £30-£215 on fleabay...SURELY NOT
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the secret to using a heat gun is " a " you must pre flux to aid the solder in flowing and " b " you must always keep the gun moving in a circular motion around the chip trying to emphasize the heat on the edges of the chip where the contacts are. If you keep the gun stationary the top level of the silcon wafers that make up the chip could indeed bubble and split so to avoid a heat concentration keep it moving!
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Cpc stock it. I thought it was about £,15 which seems to last most engineers about 6 months
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I totally agree with whith whats being said about Chipquik..
I discovered this stuff about 2 years ago ..but in those days you had to send to the USA for it ..
which made it damned expensive as you don't get much for your money ..
Having said that ...you dont need much per job ..
And if your a cheapskate like me ;)
you can re-use sizeable pellets saved from a big job to do a smaller job ...so I even keep those ..
A fresh application of the dedicated flux gets you 2 or even 3 desolders from one small length.
That solder is the best thing since sliced bread ...and I wouldn't be without it ..
It even encourages me to remove an read eproms and flashes ..in working sets ...to start building up my archive..
Whereas Id be apprehensive about doing this usually ..in case the pads or fine tracks where damaged in the process..
Its still a bit too expensive imo ...but then its copyright is protected ...
Damned good stuff though..
rgds
Evan
..Another application worth mentioning ..
Its not just SM devices that benefit ..
I recently had cause to remove and re-dress the contacts on the 2 main power relays on an Hitachi Plasma TV ..
Very tight fit on the through board connections and little hope of freeing them up with an aspirator or solder wick ..
a small application of chipquik on each leg of the relay kept the conections fluid enough to pop it out with no damage ..
The holes the re-warmed and aspirated to clear ..
Contacts cleaned ..and the relay relays refitted..
Job done...
So great stuff for tight fitting through hole components ...particularly on double sided print pcbs..