Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

[jesus.cantu]

Hello Dudes

I still having the problem with my LT716S monitor, I´ve just recapped 1 week ago and it stills the same, someone can give me a Hint, please ! my desk is going to fail, it cannot suport the old and big CRT monitor, and neither do I...

So thanks in advance for your Help, I hope read you soon.

[jesus.cantu]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

Please !, somebody could tell me why I get no answer, did I made something wrong ?, please tell me what !... so I can fix it !, or if there is no solution known to my problem just type it please, Or maybe it is for my english... I can read it and undestand it but is because of I wrote it and maybe am not as good as I wish, I mean it ´cuz I am from Mexico.

Well thanks a lot, I´ll wait for your reply !

[kc8adu]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

start by posting pics of the boards.a mag could be anything.

[jesus.cantu]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

Sorry, I was on a Buissnes travel. Here you have a pic of a power board exactly like mine.

[Crasoum]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

You said you recapped? Did you make sure the polarity of the capacitors was correct? For my mag, I want to say I replaced all 6 of the big ones with 470uF and the farthest right one with 220.

You may also need to replace C10 C11 with 100uF 25V.

The fuse could also be bad, lower left, the white thing.

[davmax]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

These Mirage boards are really poor quality including caps. You have replaced caps as step one. The fuses should be checked but doubt this is problem, two fuses lower left and just right of centre both should measure zero ohms.
Inverter transformers should be checked for winding resistance, compare the two they should be the same. I suspect one has failed. Check the two blue caps left and right above centre they must be perfect , no short or loss of capacitance, they are used to limit the current to the CCFL tubes. Often the inverter switching transistors fail, not visible in photo and possibly under the board, the symptoms suggest that they are OK however check each terminal pair for a short, there must be no short circuit (zero ohms).

It is highly likely that if a transformer is gone that you can only fix with a replacement board. Transformers are notoriously hard to get as a seperate item.

[davmax]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

Possible inverter transformer source: http://www.lcdinverter.co.uk/coils.htm

[jesus.cantu]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

Crasoum and Davmax: Yeah !, I´ve just change the six 470mf and the one 220mf, now I'll try double-checking the 100mf little ones you said... and check again the fuses you said (I really didn´t take a good care while checking them), and the inverters transformers, maybe there will be the problem. Thank you very much !, and as soon as I can put my hands on it, I´ll write you back, Thanks you very much again !

[davmax]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

I have put together a checklist.

Failed Monitor back light

Fault finding check list.
1. Check back light CCFL tubes to make sure that they are not broken.
2. Check all electrolytic capacitors for bulging tops and electrolyte stain (red/brown). Replace all caps with these problems evident.
3. Check the switching transistors that power the inverter transformers for a short circuit between the centre leg and the other legs. If there is a short circuit remove the pair of transistors.
4. If the transistors have failed short circuit check for a circuit fuse that may be blown or high resistance. Normal resistance is zero ohms. Additionally check for series regulating transistors that supply the failed switching transistor/s, there must be no short from the centre leg to the other legs. Replace if faulty.
5. Check the inverter winding resistances. The low voltage primary resistance should be less than 0.5 ohm. The high voltage output winding should measure between 500 and 1000 ohms. There are usually two transformers, compare the resistance readings, they should be approx. the same.
6. Make sure that all connections to the transformer are soldered well. To be certain heat each connection and reflow the solder using some new multicore solder.
7. There are usually several blue high voltage output capacitors that supply the CCFL tubes. These should be checked for a possible short circuit. Ideally they should be checked for capacitance value. These caps seldom fail hence they are last on the list.
8. Replace faulty inverter switching transistors once steps 4 to 7 are completed.

This above steps will cover the most common inverter failures. Powering up is the next step.

[terry]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

Hi, I have a proview 700p with the inverter transistors blown, these are marked (D444) has any one got a data sheet for these or where I can get some from.

Thanks for any help

Terry

[davmax]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

The D444 will be difficult. This seems to be a manufacturers part number. Most transistors have a four digit number. Do you have one transistor that is not blown. This can be measured to get an idea what might replace it ie it most likely is either an NPN bipolar or a MOSFET, they measure very differently. Let me know if one is not shorted.

[vince88]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

I just opened a MAG Innovision LT716S that does not power up. The power board is another typical case of 'bad caps' bulged and 'oozing on top', as shown in the 2nd picture. These caps are all on the secondary side of the power supply: seven Xunda capacitors, including six 470micF/25V/105deg and one 220micF/25V/105deg. I recapped the board with capacitors bought at HSC in Sunnyvale: six 470mF/25VDC/105deg and one 330mF/25VDC, see enclosed 3rd photo. The LCD now is fully functional. Note on the 3rd photo that the output pins of the power board are clearly marked for testing: +5VDC, +12VDC, GND, BRI, LPON.

[Danblade]

Re: Mag Innovision LT716S no power whatsoever...

I have this newer version of the power board, yes it does have the burn marks on the board. I am thinking that the two small caps are bad. (not sure how to test...).

[retiredcaps]

Re: Mag Innovision LT716S no power whatsoever...

I have this newer version of the power board, yes it does have the burn marks on the board. I am thinking that the two small caps are bad. (not sure how to test...).

Some browning the pcb is normal because the fets on the underside get hot from operation.

In order to test a cap, you need an ESR meter which costs $60 to $300. If you think they are bad, it is just cheaper to order new caps.

PS. You never did say what is wrong with your monitor.

[Danblade]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

Sorry about leaving the problem in the title only. The Problem is that there is no power light on the unit. After checking the pins with a meter, the most voltage I see is 0.1 volts DC.

[retiredcaps]

Re: Mag Innovision LT716S 700P lasts 2 sec on and then it goes off

After checking the pins with a meter, the most voltage I see is 0.1 volts DC.

1) No power can be due to an open fuse. A good fuse should measure less than 1.0 ohms.

2) The angle of your picture makes it hard to spot the fuse, but the fuse should be around the brown plug and marked on the pcb board with something like F100.

3) We prefer top down pictures like this composition and clear enough so we can read the pcb designations.

https://www.badcaps.net/forum/showpo...94&postcount=1

4) If the fuse is good, then CAREFULLY, measure the DC voltage across the large filter capacitor (the one lying on its side). If it is working, this will be HIGH VOLTAGE. It should be around 165V to 170V DC.