Mag LT916s Model 900p 19" LCD dropping like flies

[phubar]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

LOL back from ebay and google, no such thing as a "cheap" ESR meter, what a noob I am...

Guys any difference between:

Ceramic
Electrolytic - Aluminum
Niobium Oxide
Poly Film
Tantalum

Thanks again!

[phubar]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Don't mean to be post whoring but can't edit my most recent message, anyways, can't order from digikey way too many options. I think I'll just stick to the 'shack or flebay.

[Michaels]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Ah, right. I guess I'll go for the 100uf ones now as severach's posts say those were bad in his. I'm not going to go so far as getting a meter I don't think.

Having tested all the other caps in circuit I start with the untestable caps C10 & C11 Xunda TL 100uf 25v. Fresh off the soldering iron they measure 35 ohms. Cooling for a few minutes they rise to around 90 ohms. Watching this happen live on the ESR meter is a great demonstration of the rule that heat reduces ESR. They are a bit hard to test accurately since only a few seconds of body heat is enough to drop 30 ohms so I leave them on the table untouched to maximize ESR.

Failure #1 >99ohm, >99ohm, 57uf, 14uf
Failure #2 >99ohm, 95ohm, 58uf, 47uf
Failure #3 >99ohm, 87ohm, 52uf, 48uf
Monitor #4: 1.2ohm, 1.3ohm, 97uf, 94uf

The capacitance is 50% it's proper value. I've seen far worse caps still operational. Only one of the 6 caps from failed monitors is so far off that the need for replacement is clear. The ESR is 100 times what it is supposed to be on every failed cap. I replaced the caps in Monitor #4 even though they haven't failed yet. My 100uf 25v reclaims have 2 different ESR averages.

Rubycon MH, Taicon VT, Jamicon TK, G-Luxon SM, Lelon LZG: 0.80-1.1ohm
United Chemicon KY: 0.16ohm (from D-Link router)

I chose the highest ESR 5 Rubycon and 3 Taicon.

This little segment, I had to read it twice just to understand it as I'm new to all of this. I'm hoping severach can come and clarify a bit on if he replaced every single 100uf, but it seems you'd have to.

[Michaels]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Hmm, anyone want to fill me in on if I broke it by putting a cap that had a lower voltage and trying to turn it on? I didn't realize when I bought a 47uf that it had a lower voltage and now I'm getting nothing out of it.

[vince88]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

I believe that Mag use the same circuitry for the 17" and 19", as shown by the enclosed pictures. For reference, here is my post on the repair of a MAG 17 titled "MAG Innovision LT716S Model 700P".
++++++++++++++++++++++
I had time today to look again at the power board [1] the primary & secondary fuses tested OK when I used a sharp probe to get through the oxide [2] primary rectifier and both secondary Schottky dual-diodes [one dual common-cathode for the +5VDC and one dual for the +12VDC] tested OK with a multimeter on 'diode test' settings. I then recapped with capacitors bought at HSC in Sunnyvale: six 470mF/25VDC/105deg and one 330mF/25VDC, see enclosed photo. Note on the photo that the output pins of the power board are clearly marked +5VDC, +12VDC, GND, BRI, LPON.
The LCD now is fully functional.

[Crasoum]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Low voltage kills the cap quicker, but if it kills it instantly you'd know.

The mag does use the same boards, the caps are guaranteed crap. Replace all over 200 IMO.

grats on making it work!

phubar don't use crap from rat shack unless you just want to do it over later and possibly kill the board. To order from digikey use caps from this thread.

https://www.badcaps.net/forum/showthread.php?t=1822

put in the series and manufacturer, IE Panasonic FK

http://search.digikey.com/scripts/Dk...panasonic%20FK

[severach]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

C10 and C11 can't be tested. Something in parallel makes the meter read 0.00 and my best 100uf caps measure no less than 0.16 ohm.

I have 4 monitors. The 3 that failed were fixed by replacing C10 and C11. I replaced them in the 4th monitor because they were already out to test and have a high failure rate. 4 monitors used 8 reclaim caps. The monitor that didn't fail might have less run time on it.

How is $75 not cheap for an ESR meter? Mine fixed 3.5 monitors.

I used a sharp probe to get through the oxide

That coating is too nice to be oxide and I've tested much older parts without stabbing them. Is there a clear coat for electronics? Would anyone producing for low bid contracts actually use it?

[kc8adu]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

the caps that read 0.00 esr have an mlcc across them.gotta pull the lytic to check.
i just replace them rather than bother testing penny parts.
i doubt any consumer stuff is conformal coated.

[vince88]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

I believe that Mag use the same circuitry for the 17" and 19", as shown by the 1st enclosed picture. For reference, here is a summary of my posts on the repair of a MAG 17 titled "MAG Innovision LT716S Model 700P, seven bulged Xunda's".
++++++++++++++++++++++
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 then recapped the board with capacitors bought at HSC in Sunnyvale: six 470mF/25VDC/105deg and one 330mF/25VDC, see enclosed 3rd photo. Note on the 3rd photo that the output pins of the power board are clearly marked +5VDC, +12VDC, GND, BRI, LPON.
The LCD now is fully functional.

[69boy]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

ok i have read everything here in this thread, cause i have a mag lt916s with the same 2 second problem and the screen goes black. i have checked the capacitors on mine and they are not blown, leaking, or buldged. insted of replacing all these caps for a waste of time, and money to no fix, i decided to try to keep pushing the bottom buttons on the monitor to bring the brightness down on the monitor, thinking that there is a heat problem, or voltage problem. so i got the brightness down to 34% , and guess what, the screen stayed on. it took me about 5 minutes to do this, off and on, off and on again, and again. right now the monitor is still on, and its been on now for an hour, and hasen't went off yet. so the people on here that replaced their caps, and it still didn't work, try this. now i know this does not fix the problem, but in my own opinion is that there is too much voltage being pulled through the voltage regulator by the lamps. my theroy is that the lamps in the screen which would be a bi%@h to get out, are the problems in this situation. they are breaking down, and pulling more voltage to run them, which causes the regulator to disconnect. because of too much voltage going through it, cause of the lamps. i believe the lamps are probely poor quality. so my screen will last a little bit longer, before it gives up the ghost. well atleast i have it for now. let me know if this works for anybody....

[wwbielsko]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Hi,

What is the Z201 Zener Diode symbol used in this inverter.

thanks for answer

[Delphen]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Ok guys, I have a Cicero 19" LCD I purchased from Futureshop a few years ago, and it had these exact symtoms. At the time I didn't know, and put it in the closet, well I pulled it out and took it apart before I wanted to throw it away.

I noticed the 6 470uF caps were all toasted, so I replaced them with 470uF 63V ones I purchased locally.

I still have the same 2seconds on, then off issue. I can't see anymore problems with the board components, and I am stumped. Anyone have any ideas on where to look next?

[Delphen]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Well everyone, I got mine fixed. I replaced all the 470uF caps, as well as the 2 100uF caps and the 1 220uF caps with all larger voltage rating ones. I also replaced one of the 250V 3A fuses near the 2 100uF caps and everything now works great.

[orzo]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Well, I give up. I replaced the 470's, 220's, and 100's just like Delphen. I did not replace the fuses It still goes black in 2 seconds. Should I replace the fuses or do anything else before I walk this to the dumpster?

[orzo]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

This forum has been great! I appreciate the help.
One other thing. My monitor seems to be always on full brightness during the 2 seconds that it is on before the screen goes black. I took a while to operate the digital controls during the 2 seconds the screen was on, but I've painstakenly adjusted the digital controls down to 9 percent with no affect. Same behaviour: Cycle the power, screen comes on bright for 2 seconds, screen goes black, green power light stays on. My wife wants the kitchen table back, so if anyone has any ideas please let me know soon.

[lapin_cool]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Hy, have the same problem on my TFT noname MJ9BNK
solved whit a replacement off caps 1000uF 10v by a 1000uF 16v.

This caps no haved wrong apparence but's dead.

Do you have an image of your power board ?

sorry for my bad english, im french....

[nintenbo]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

ive also repaced the caps and one resister that was burned, but the 3.15 A thermal fuse i dont know what temperature it should be and ive only got a 20/40 Amp thermal fuse which is a little too many amps lol

[arneson]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

These are what I have found in camcorders and on the bigger inverter boards.
They are sometimes in a holder and sometimes soldered onto board both surface and thru lead.

There are smaller and larger versions of these fuse devices but this size is very handy.

[ahester]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

I replaced all caps but I don't know C12/C13

5PF or NF? I think PF.

these caps are unusually

[Hedgehog52]

Re: Mag LT916s Model 900p 19" LCD dropping like flies

Just wanted to say thanks for this thread. I have a ProView PL916 that has been sitting in the corner, dead, for months. It's my preferred monitor because it has no bad pixels. After reading this thread, I noticed the bulge on all the xunda brand caps and realised they were all shot. I replaced them with Nichicon UPW caps, and all seems well.

Thanks!