Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Ok, good point, will do.
Good tutorial at that site. I think I'll re-solder these joints and re-test - as a first step....
jonathanku
Keen Tinkerer
Last Activity: 01-05-2011, 09:07 AM
Joined: 06-29-2010
Location: Scotland
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Thanks for that. Do you have any thoughts on whether this darkness looks like blackening of the lamps?
Also, can you give any advice on removing these lamps? I can't see how the wires or rubber ends come away from the lamps and the metal supports......Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Hi folks, I've got some time off for Christmas, and the baby's asleep - so I took another look at this.
I was getting two seconds to black with each different CCFL unplugged, so I got myself another monitor, a 15" dell, and plugged its CCFLs in to the Lenovo circuit, and I was getting the monitor to stay on. With just one of the plugs from the Dell in it stayed on for around 20 sec. With a pair of plugs, it seemed to be good for minutes until I switched it off.
I'm guessing that...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Yeah, I had done all but the last part of post #16 suggestions. So disconnecting each ccfl one at a time didn't change anything and trying each ccfl in each connector one at a time was the same. I didn't have a "known good" ccfl to complete that test.
But if I get hold of another monitor (don't tell the wife), I'll test connecting the bad monitor to the CCFLs of the good one. Point taken about keeping the monitors seperate... and I've read the posts about larger and smaller ccfls. Thanks...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
OK, thank you for that, I appreciate the information and advice. Warnings heeded.
Can I ask a question about the CCFLs - do they come in different sizes/ratings etc.. Will my monitor be fussy about CCFLs from another monitor (for testing purposes)? Do I need to find another similarly sized monitor to take the CCFLs from, or will a little 15" monitor do the trick?
-JKLeave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Ahh! Hopes dashed at the last second.
I soldered a 10k resistor across that diode D210, and it looked like it got round the issue. So I packaged it all back up etc. and plugged it into the PC... looks like I bought myself another 15 sec or so. It now goes black after about 20sec.
I also soldered a futher 1.1k resistor across teh 10k so it'd be around 1k I guess, but still only get about 20 sec.
Before I dig even deeper into the monitor, can I just ask - if shorting D210 keeps it on,...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Thanks, I'll attempt this again. Last time I pared the monitor down to an enclosed metal unit (with the screen on the front) and the CCFLs must be within that, but I ran out of time an re-assembled it. I'm also planning on testing a resistor across D210 to see how that goes since shorting it seemed to help. I understand that this is just masking the problem, but it might be sufficient.Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Thanks retiredcaps. It settled on 0.2 ohms.
I don't really know what else to do now. I'll try and find my way in to the CCFLs and look for any signs of problem. Maybe picking up another broken monitor to test out spare CCFLs would be a good idea.
(in the back of my mind though is that there was no difference in behaviour when I disconnected - or only connected - each CCFL in turn) Hmm.Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Guys, I'm not sure if you can think of any further systematic testing I could do?
I've since re-soldered a few points which looked potentially dodgy (at least to the untrained eye) C901 and another couple of points near the PT201, but still getting exactly the same behaviour.
I also started measuring the resisters to check for any shorts. R926/R927 gave a short beep with my continuity check... but I'm guessing that's because of the capacitor in parallel with them. I reversed the probes...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
OK - R230 is 0.474 as you suggest. Looks like it's in parallel with C223 - I guess that could affect the in-circuit reading. Now how do I get something soooo small back in the circuit?! ---ok managed. Smallest thing I've ever soldered.
Back to D210... I've now bought another replacement just to check, and it's reading open (i.e. "1." on the meter) and ~0.89. Maybe these diodes have been ok, and it's just the meter giving an unexpected reading? Looking at my meter - the diode setting is within...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Thanks...
R229 0.670 on the 2k scale
R230 0.237 on the 2k scale
R 231 12.3 on the 200k scale
R 232 50.7 on the 200k scaleLeave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Yeah - 1. is the diode reading when not connected. And yes, I only bought 1.
I have noticed though, that this is the same reading as I had with the old diode. But if they both blew when connected to the monitor, that might explain it - assuming there's a different root cause. I'll get another couple tomorrow and test them both [u]before[/u] connecting them to the circuit.Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Yeah - 1. is the diode reading when not connected.Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
OK, not sure what's going on. I got a 1N4148 from Maplin and soldered it in temporarily in place of D210 (making sure the black band was at the same end as the old D210), but got the same 2 sec to black behaviour.
I measured the diode in place and was getting the open reading in one direction ("1.") and 0.8ish (didn't record it) in the other direction.
Having taken it out the circuit again, I measured the diode and got the same, "1." and 0.899. I'm now kicking myself...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Well, unfortunately, the diode crumbled as I removed it. Either I was too heavy-handed, or it already had physical flaws - I don't know.
I'll get a replacement (i.e. [URL=http://www.maplin.co.uk/Module.aspx?ModuleNo=19076]one of these from maplin.co.uk[/URL] tomorrow (Mon) as I work near one of their stores.Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Well, unfortunately, the diode crumbled as I removed it. Either I was too heavy-handed, or it already had physicalLeave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Excellent. I'll do these tests - it'll need to be tomorrow - and check local suppliers for a replacement.Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Here's D210 close up.
If this needs replaced, any idea on the type/rating etc.?...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
el3ctroded - I've not yet de-soldered one side of D201, I'm not the most confident at desoldering and resoldering, but will if it's necessary...?
In the mean time, I've done PlainBill's test and shorted across D210 (didn't have any resistors handy) and this [i]did[/i] allow the monitor to remain on. I left it for about 5 sec - definitely longer than it used to stay on. Does that mean D210 is the problem, or just an indicator of another problem?
Thanks. -JKRe: Lenovo ThinkVision L191Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
Hi again, interesting info. And you're spot on.
1. R225, R226, R227, and R228 are 0.98, 0.97, 0.98 and 0.97 on the 20kΩ scale.
2.
D202: 0.780 / 0.866
D204: 0.780 / 0.860
D206: 0.780 / 0.863
D208: 0.786 / 0.867
3.
D203: 0.870 / 1.789
D205: 0.863 / 1.781
D207: 0.862 / 1.783
D209: 0.865 / 1.785
4.
D210: 0.900 / 1. (this is how the meter displays it... though "1." is also displayed...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
I'm getting [b]0.09[/b]. Note I opted to put the other probe on one of the four nodes to the left of the screw-hole by the RoHS logo. Is that suitable?
Yes it does.Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
I'm getting [b]0.09[/b]. Note I opted to put the other probe on one of the four nodes to the left of the screw-hole by the RoHS logo. Is that suitable?
Yes it does.Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
...Leave a comment:
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Re: Lenovo ThinkVision L191 19" goes blank after <1 sec
No shorts on these.
I'm not too sure what to expect for the diode - the meter's diode setting says 2k, and the two readings I got were:
0.266
0.729
I'm not sure of this one. I can see the J921 label on the rear of the board, but not sure which connection to check. On the front of the board, there looks to be a space for a connector, but with nothing there (just the white printed line).
See attached....Leave a comment:
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