Re: Asus VW192S revived, but backlights on then off
No, no recap on the primary side (i.e. c101, 103, 105).
Should I change that as well?
Oh, I've also checked the HV transformer driver mosfets Q208 & Q207 for resistance and they showed 1.5 to 2.8 MOhm between pins.
amach
Member
Last Activity: 11-17-2022, 02:55 PM
Joined: 12-19-2012
Location: Athens
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Re: Asus VW192S revived, but backlights on then off
OK, I have managed to recap the inverted part of the PSU (caps 153, 154, 159, 160, 203, 204) and also changed the 2 caps next to the voltage regulator on the logic board (c30, c31).
The same few sec to black problem still remains, however, I've noticed a larger period of backlights ON state, 4 sec vs 2 sec previously, before shutting down.
I've also test logic board regulator (in circuit) for shorts and its resistances seem normal.
I've tested the inverter transformer (T201) for open windings (in circuit)...Leave a comment:
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Re: Asus VW192S revived, but backlights on then off
Unfortunatelly I have no test bulb or ESR meter, just a dmm. I'll try to replace as many caps as I can.
Which component is the "regulator on the logic board".Leave a comment:
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Re: Asus VW192S revived, but backlights on then off
Anybody willing to help me on this, please ?
Even a general direction would help, as I'm totally lost.Leave a comment:
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Asus VW192S revived, but backlights on then off
Hi again.
This time I got a monitor out of the recycle bin. It struck me that it had speakers. Sounds useful.
SUMMARY
=======
Monitor is an Asus VW192S, 19" LCD screen 1440x900, model of 2007.
Initially, the monitor had been completely dead.
THINGS TESTED
==========
1) On the power board, at first, I checked the main fuse, which was indeed blown. As soon as I replaced it, it got blown again rather violently.
2) Then, I de-soldered transistor Q101, an N-channel MOSFET switching regulator (Toshiba 2SK3562... -
Re: LG W1942S won't backlight, but LCD is OK
Finally, I replaced the faulty mosfet with a new one bought on ebay. The P-channel tests fine now.
Not being skilled on soldering, I post a few close-ups for you to comment on.
The backlight now comes on and the screens works as seen on the last photo. No buzzing transformer as well.
Congratulations!
Thanks to all the forumers who contributed to this thread, especially selldoor who offered to help sourcing the mosfet....Leave a comment:
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Re: LG W1942S won't backlight, but LCD is OK
I finally managed to secure an AP4525GEH from spain on ebay. I'll post when I receive, test and solder it.
A friend working in a bank tipped me that some categories of electronic parts are exempted from capital controls. There is no consistency though, and in my experience on ebay, it is a matter of trial-and-error.
The revolution will have to wait.Leave a comment:
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Re: LG W1942S won't backlight, but LCD is OK
You are right, I have already tried that. But talking to him on the phone reveals that, actually, there is no stocked item. Minimum order from abroad applies here, too, similar to any other (inland) supplier I have come to contact with.
Thanks for your interest, though.Leave a comment:
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Re: LG W1942S won't backlight, but LCD is OK
Unfortunately I can't source this smd mosfet, locally. Greek suppliers have a policy of minimum order of 10 pieces at 6 euros each!
On the other hand, ordering from abroad is blocked due to current capitol control on Greek banks. Buying on Ebay (& paypal) is impossible, as money cannot be transferred abroad, even involving few euros.
I've hit a wall here.
Is it possible to use common through-hole transistors/diodes combination to replace this item?Leave a comment:
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Re: LG W1942S won't backlight, but LCD is OK
Sorry for the delay, I had been away for the weekend.
@retiredcaps I cleared the the backsides' solder splash by Q302. See photo.
@fzabkar thanks for the links.
I 've just desolder mosfet U303 (4525GEH), with some difficulty, i.e. little burned finger while touching the neiboghring large ground pad! Not really skilled on this task.
Off-circuit dmm measurements:
S1-G1 OL
S1-D1/2 OL
G1-D1/2 OL
S2-G2 31 ohms
S2-D1/2 0.3 ohms
G2-D1/2 31 ohms
...Leave a comment:
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Re: LG W1942S won't backlight, but LCD is OK
Just tried this. With CCFL lamps unpluged one at a time the buzz won't go away. I have noticed, it starts for a second, mutes for one more, and then restarts buzzing without end.
I need some time to desolder the mosfet to check it out of circuit.
Thanks for directing me on this.Leave a comment:
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LG W1942S won't backlight, but LCD is OK
LG W1942S won't backlight, but LCD is OK
Hello,
After few years of calm, another LCD screen failed on me. An LG W1942S monitor needs my attention and repair. But I need your help, once more.
I hope the photo are acceptable.
SUMMARY
======
This is a LG W1942S made probably in 2008. The backlight won't power on, at all. The LCD matrix shows the (faint) computer vga signal alright. When I press the power button the power LED turns blue, as normal. The rest of the buttons and menus seem to work.
THINGS TESTED
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Re: LG 37LC2R, backlight shuts down after 4 seconds
Just to inform the fellow-forumers that I couldn't find the transformer, anywhere on the internet.
Instead, I purchased form ebay (32 euros incl. ship.) the whole inverter board extracted from a SAMSUNG LE37R74BD or 37WLT66.
My tv now works flawlessly.
Thanks for your advice.Leave a comment:
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Re: LG 37LC2R, backlight shuts down after 4 seconds
The actual part is T51.0059.210B and not .2108. The print is vage but google search had the final word.
I have found it on eBay, 16€ incl. shipping, pricy considering the whole inverter lists for 18€ plus shipping. I am searching and considering my options.
Any way to bypass this transformer-lamp sensing?Leave a comment:
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Re: LG 37LC2R, backlight shuts down after 4 seconds
I already have a service manual (which I attach), but I cannot find the HV transformers. Part number on board is T403.
The prints on it is:
"T51.0059.2108 G1"
"0639 01 8 J"
The inverter board model is vit71010.53 .52 .51
Not at all, please provide me with a link.
Any source for this transformer?...Leave a comment:
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Re: LG 37LC2R, backlight shuts down after 4 seconds
My god, you are absolutely correct! Thank you very much. Pair (1,3) is the primary and (4,5) the secondary. Pin 4 seem to connect also to sense circuit. Pins 2 & 6 seem to stand unconnected.
Sorry, I had been careless on my previous measuring between (4,5) due to surface flux. Now ratings are far from 0L. Here they are for each quad of transformers:
1.737, 1.742, 1.743, 1.728 kΩ
1.742, 1.760, 1.764, 1.757 kΩ
1.745, 1.760, 1.736, 1.753 kΩ
...Leave a comment:
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Re: LG 37LC2R, backlight shuts down after 4 seconds
Auto-ranging, even tried manual.
I'll try remove one of them, if there is no alternative.
First picture shows transformer's primary(?), with my indications of the board pin numbers. Second pic the secondary(?) pins.
Next 3 pics the results at pins (5,6), (1,3) & (1,4)....Leave a comment:
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Re: LG 37LC2R, backlight shuts down after 4 seconds
What baffles me is that I take 0L (auto-scale or manual Ohm) on every single of the 20 transformers secondaries, that is pins (5,6) on my prev post....Leave a comment:
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Re: LG 37LC2R, backlight shuts down after 4 seconds
Thanks to all replying.
Everything works as normal besides back-lights. Look at first picture.
I had attached a few pictures on my original post via "manage attachments" which originally showed up fine, but I can't see them anymore. Perhaps web server rejected them, later, on a second thought, as bigger than expected (2592x1944).
New ones reattached (pics 2 to 5).
I rechecked the 24V line to inverter, on the PSU socket and got 24.8V with lamps off and 24.2V...Last edited by amach; 01-07-2013, 07:38 AM.Leave a comment:
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LG 37LC2R, backlight shuts down after 4 seconds
Hi everyone,
I have searched the forum but couldn't find a thread with my exact model and problem. Please forgive my language errors.
Without any other worrying sign, after 5 years of impeccable service, my TV stopped showing picture.
The pattern is this: TV being in standby (red light), after turning it on by the remote or the panel buttons, the light flashes 3 times, and turns white-green (as normal). The panel shows fine for 3 to 4 seconds and then blacks-out. Nevertheless, sound goes on. If I put it in standby, I can replay the previous pattern as many times....
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