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Old 12-14-2017, 12:48 PM   #1
eccerr0r
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Default Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Well I think every single one of my 19" LCD monitors had a problem or died at least once now... all either bad caps or suspected bad caps.

Anyway, my 900G completely would not turn on anymore after flickering on and off for a few days. While disassembling it, I noticed the LVDS cable that attaches the main board to the T-con board (?) was glued together. Well, I had to remove the glue, then proceeded onwards. After finding the bad capacitors and replaced them with what I had on hand, I put it back together and powered up...

It was white for 2 seconds and then faded black.

Weird. Same behavior with a DVI signal. Ugh. Did I break the mainboard?

Well, turned out the LVDS cable was loose. Really loose. Probably because I ripped off the hardened ceramic-like glue. For now I used some black tape to stick the wire... don't think it will hold long, but I figure that (A) I know what the symptom is now and (B) I figure I'll be back as the caps I used aren't very good (I need to restock...badly...)

Long story short: Use hot glue or what removable glue do you use for this kind of situation?
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Old 12-15-2017, 07:11 PM   #2
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Hmmm... I've seen factory LVDS cables glued down with double-sided foam and/or aluminum tape, and I've always been able to remove it carefully without damaging anything. Afterwards, I never re-glued it with anything if the original adhesive tape didn't want to hold it back.

Regarding the white screen you saw: that's typical when the LVDS cable is not connected properly or when the T-con board has one of its TFT panel inverter power circuits go bad or the LVDS driver chip and/or its linear reg. go bad.

Yes, if you didn't use good caps, you will be doing this again. LCD monitor PSUs tend to run quite hot at normal room temperature (i.e. 70-75F or 21-24C). I've measured 70C inside the case of one of my 19" LCD monitors when the room temperature was close to 30C. I imagine with a lower room temperature, that may drop down to 55-60C, but that's still a cap-cooker if you use general purpose 2000h caps. CRTs often appear to run as hot, but they have much more space inside their cabinets, so the components don't actually run anywhere near as hot.... save for the CRT neck board, maybe.
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Old 12-15-2017, 10:02 PM   #3
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Hmm. the original stuff was actually something that set hard, almost rock hard. It wasn't just tape to hold it in place though there was some metal foil tape.

I wonder what the hard stuff was... Definitely felt harder than hot melt glue or RTV.

BTW, the caps this monitor used were all samxon GF(M) U2A's - supposedly 105C low esr's. All of them...

Last edited by eccerr0r; 12-15-2017 at 10:04 PM..
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Old 12-16-2017, 10:27 AM   #4
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

No idea what that would be. Perhaps they spilled Threadlock on there by mistake?
If you want to use hot glue to hold stuff down, it will work fine - even in a hot LCD monitor. I've used it before and it's not a problem. If the LCD gets really hot though, you may get a bit of a hot-smell glue coming from the monitor. But it won't melt away or anything like that.

Samxon GF c[r]aps are known to go bad, especially in monitors. They are indeed low ESR, but nothing special. IIRC, even Panasonic FC could be used as a substitute, and that's an entry-level low ESR cap series.

Last edited by momaka; 12-16-2017 at 10:28 AM..
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Old 12-16-2017, 03:38 PM   #5
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Doesn't appear to be threadlock, usually that stuff is watery and dries down. This stuff is white and like a blob, perhaps it's a different formulation of hot melt or maybe some type of epoxy. Either way I don't think they intended it to be removed. Then again hot melt/epoxy weren't meant to be removed either, just that it was so hard that trying to remove it probably caused damage to the connector whereas hot melt and RTV remains pliable after setting.

As it was a stop gap solution, I found three of those Samxon crapacitors to be really bad and just replaced those (just one was slightly bulged, other two looked fine on the outside). There were a few others that were marginal but I didn't replace them as I didn't have any replacements on hand. This is a death trap monitor, will die at any moment... heh heh heh...
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Old 12-16-2017, 04:20 PM   #6
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

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This is a death trap monitor, will die at any moment... heh heh heh...
Lol.
A lot of LCDs are.
On the worst ones, I drill extra holes in the metal cover and/or plastic case. A lot of times, the plastic cover has enough holes, but the metal cover has tiny holes that restrict a lot of the air flow. Those are the easiest, as I just grab a bigger drill bit and widen the small holes. It makes a mess in the garage with steel shavings, though. Not to mention you definitely need to remove all boards from the metal cage if you want to do that.
But it does help a lot with the cooling.
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Old 12-16-2017, 09:44 PM   #7
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

I notice there's a lot of aluminum tape, which leads me to believe that RFI is a concern... I do notice this monitor seem to cause my radio to generate noises so I'm a bit worried about RFI as well...

BTW, the bad trio... Just that 470F looks a little phatty, but all three needed to be replaced else the monitor wouldn't power up anymore.
Attached Images
File Type: jpg samxon.jpg (237.6 KB, 18 views)

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Old 12-19-2017, 03:48 AM   #8
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

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I notice there's a lot of aluminum tape, which leads me to believe that RFI is a concern... I do notice this monitor seem to cause my radio to generate noises so I'm a bit worried about RFI as well...
I guess if you have lots radio and HF gear, that might be a concern. But I personally never bother putting that aluminum tape back on, mostly because the original never wants to stick back on. You could use new aluminum take (I even have a big roll in the garage... but I never bother lol).

Quote:
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BTW, the bad trio... Just that 470F looks a little phatty, but all three needed to be replaced else the monitor wouldn't power up anymore.
That means probably all of the Samxon GF caps in the monitor need to be replaced (save for the big input cap on the primary).
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Old 08-27-2018, 04:01 PM   #9
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

After about 6 months of it working just fine, it crapped out once again.

I replaced a few more of the capacitors and it's up and running once more. The count is now 9 capacitors swapped, and includes a capacitor that's >5 ohms ESR, and the rest around 1 to 2 ohms.

I ran out of 470F capacitors, but since there were two in parallel I stuck in a single 1000F in place of the two 470s. As it looks like they tried to reduce BOM line items since they used 25V caps on the 5V lines, it probably will be fine... for how long...
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Old 08-27-2018, 05:17 PM   #10
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

thermal adhesive maybe . bit expensive for sticking cables though .but maybe not to the industry in large amounts .
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Old 08-29-2018, 05:54 PM   #11
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Don't know... thermal adhesive hardens to a ceramic-like consistency (at least it was like that when I removed it), and "sticky" enough like hot glue? This stuff was definitely like a ceramic in texture, but rips right off.

The other end of the connector has a rubbery compound gluing the connectors together, and may very well be hot glue.

Incidentally of course I had to disconnect to fix this again. This time I didn't use tape or glue or anything, and was able to reconnect it, luckily it's still holding as I'm using the monitor now. I wonder when I will have to go repair the monitor again, some day down the road...

Back down to just one monitor in my "inbox" to repair, another 19" 5x4'er.
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Old 09-01-2018, 03:17 PM   #12
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Quote:
Originally Posted by eccerr0r View Post
After about 6 months of it working just fine, it crapped out once again.

I replaced a few more of the capacitors and it's up and running once more. The count is now 9 capacitors swapped, and includes a capacitor that's >5 ohms ESR, and the rest around 1 to 2 ohms.
I hate to say it... but I told you should have done a full recap.
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Old 09-01-2018, 07:36 PM   #13
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

yeah, I know, I know... just that I don't have spares on hand for the next emergency - and I'm not a repair shop...
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Old 09-02-2018, 01:23 AM   #14
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

I understand, I have some devices that probably should be recapped and still haven't (that I use quite a bit) - i.e. PSUs with Teapo and other less-than-nice caps. But my usual policy is, if there are no bad caps and the device works, I leave it alone. Once a single cap crops up (I check some of these devices periodically, if they are easy to check) I do a full recap, as I know all of the other crap caps in the device are probably on their way out.

That said, I do keep a few spare caps, as I almost always buy in quantities of 10. On Digikey/Mouser, it's often cheaper to buy 10 caps rather than 5-7 individual caps. And I find that many repairs (especially LCD monitors and PSUs) always need more than 3-4 caps of the same type. So I buy in bulk of 10 or more, use what I need, and the spares stay for emergency situations.
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Old 09-02-2018, 08:15 AM   #15
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Yeah, even 10 may not be enough, some times I eat through a specific value really quickly and sometimes they sit there year after year, and maybe they too become bad from age.

The cost of these caps add up. Yes the price break is the main reason for getting 10, though the 100 mark looks really tempting. It just feels wrong when you order 100 pieces of 50 capacitors, paying a $50 order to repair a monitor not worth $50 even if you're not even close to using all of the capacitors...

BTW, dang, shipping costs are expensive. Costs add up. I have a mouser order just sitting there because I need shipping costs to be a smaller fraction of the total order cost. Grr.
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Old 09-02-2018, 08:53 AM   #16
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

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Yeah, even 10 may not be enough, some times I eat through a specific value really quickly and sometimes they sit there year after year, and maybe they too become bad from age.
Same here.
I have caps from as far back as 2009. But they still read good on my meter. In fact, I just used a few from those a few months back and the repair went fine. Also, I reformed many of my caps I think back in 2015 and some in 2016-2017. So if you care to reform them once in a while (maybe every 2-3 years, they should be good to go for any repair right out of the package.)

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The cost of these caps add up. Yes the price break is the main reason for getting 10, though the 100 mark looks really tempting. It just feels wrong when you order 100 pieces of 50 capacitors, paying a $50 order to repair a monitor not worth $50 even if you're not even close to using all of the capacitors...
Agreed.
I think I've ordered in quantities over 100 only on one occasion (from BCN), but it was for recapping around 30 OEM desktop computers all with the same mobo, and BCN store actually had the best price on the polys I needed. Also the company budget was higher than what I came up with (i.e. I still saved them lots of money in the long run), so cost wasn't that big of a deal.

Otherwise, I've been thinking of getting 100 or so Rubycon ZLH, 6.3V, 820 uF caps, as 6.3V @ 820/1000 uF is quite often used on older mobos - which I have many of that need a recap. So I'm still thinking about it.

Main problem is shipping, like you said: both Digikey and Mouser have gotten a lot more pricey than they were back in the day. Some years back, I could make a small order of caps/parts and have a tiny box shipped from either company for like $3-5. Now, they almost always go for the larger $10-12 box, even when I don't have that many stuff. (They do it based on weight thresholds, I think. And before, I think it was just either volume or small flat rate).
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Old 09-02-2018, 12:20 PM   #17
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Also having to get all different lead spacings, diameters, and heights of the same capacitance...

Those two 470F capacitors I replaced with a 1000F? I mounted the tall cylinder parallel to the board to deal with the height problem... increase in ESR and ESL but a missing capacitor is worse. I suppose more "creative fitment" needs to be done in the future when substituting (on a side note, there was a row of capacitors side by side on the board. It would have provided an airflow impediment, and mounting that capacitor parallel and slightly off the board opened a gap between the capacitors, breaking the artificial baffle... it might make the capacitors run cooler and thus longer!

Incidentally, I'm out of good 1000F caps now too. I still have a pile of "caps" but using those capacitors will surely result in a redo down the road...
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Old 09-04-2018, 02:43 PM   #18
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Default Re: Gateway 900G 19" LCD monitor: LVDS cable GLUE?

Quote:
Originally Posted by eccerr0r View Post
Also having to get all different lead spacings, diameters, and heights of the same capacitance...
Yes, sometimes I have an issue with that as well. But if I really need to do a recap and can't wait for the proper size, I'll just substitute something else, depending on what the circuit can take. (Like you, maybe one 1000 uF cap in place of two 470 uF ones, or vice versa).

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on a side note, there was a row of capacitors side by side on the board. It would have provided an airflow impediment, and mounting that capacitor parallel and slightly off the board opened a gap between the capacitors, breaking the artificial baffle... it might make the capacitors run cooler and thus longer!
Yup, that's possible too.

Some monitors are way to crowded, though. Or they lack adequacy of ventilation holes. Either way, what I've started doing lately on some monitors is widen all of the ventilation holes, if they are very tiny. And if none exist on the bottom but there is space for them, I drill out new ones. It's a somewhat time-consuming process, as I have to strip down the monitor plastics and metal case from the electronics completely so that I can drill the holes. And then I have to clean and deburr the holes from metal shavings. All-in-all, not my favorite thing to do, but on the few monitors I did it, it seems to make a big difference - monitor feels very warm at the top side of the back, but cool on the bottom side. So that means convection cooling is working well inside the PSU "box".

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I still have a pile of "caps" but using those capacitors will surely result in a redo down the road...
Oh boy, I only vaguely remember those cap guns, but they were pretty cool. I used to have one when I was 5 or 6 years old, but I think it got thrown away for some reason. IIRC, it was pretty heavy, so probably Zinc cast.
Ironically, I still have/keep most of my cheapo BB guns from when I was a little older (7-10 years old).

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