Benq Q9T3 wont turn on, need help!

[Adasm]

I inherited a dead Benq Q9T3 monitor from a friend and after reading this forum, there seems to be a light at the end of the tunnel.
I've included a pic of the power board. This monitor wont turn on whatsoever, no lights, no screen nothing. So, i'm assuming it's a power issue. The components of the board seem to be okay, but that could mean nothing. There seems to be some "burnt" spots on the board which the pic shows, but I dont know where to check from here, hopefully you all can help me in this predicament. I havent checked the fuse yet as i'm hunting for my MM right now. But will update soon on some component checking. Thanks in advance!

[sofTest]

Re: Benq Q9T3 wont turn on, need help!

Well, from the picture, it looks like 3 or 4 capacitors on the lower right in the picture have bulging tops.

[Bobdee]

Re: Benq Q9T3 wont turn on, need help!

Dont like the look of that right hand side Inverter Transformer either, looks like it has suffered some over heat damage.

[Adasm]

Re: Benq Q9T3 wont turn on, need help!

Awesome, progress. Now, how do you suggest I test these components? I know basic fundamentals of electronics and can test them/replace them. But these components I don't know how to test.
If the tops of the caps are bulging and not flat, I take it that's a bad sign? A precursor to "leaking"?

[sofTest]

Re: Benq Q9T3 wont turn on, need help!

If a capacitor is bulging, it is defective, yes. If you choose to try to repair the board, all bulging capacitors need to be replaced with a good quality replacement.

[Adasm]

Re: Benq Q9T3 wont turn on, need help!

Good, I can do that. There is a great electronics store nearby I can get caps from. Now, how about this suspect inverter transformer? How do I test that? Also, how do I test the caps with my multimeter to know 100% that they are defective?

[sofTest]

Re: Benq Q9T3 wont turn on, need help!

On some multimeters you can measure capacitance and resistance, but that will not tell you 100% that a capacitor is good. The best tester for a capacitor is an ESR-meter. A bulging capacitor is bad, no need for further testing.

Also, you can't just replace a capacitor with any capacitor with the same markings (voltage and uF). The replacements usually need same or better specification impedance/ESR and ripple than the old ones. This is data you have to look up on the datasheet for a capacitor.

[Adasm]

Re: Benq Q9T3 wont turn on, need help!

Alrighty. Now how do I discover the ratings of the existing bad caps on the board? I examined and found 5 bulging capacitors:
1000uF 16V 2pcs
1000uF 25V 2pcs
470uF 25V 1pc
All are electrolytic 105 degreee caps too. Now, do I need more info about them than this? What do you suggest I replace these with? And what about this suspect inverter transformer?

[Bobdee]

Re: Benq Q9T3 wont turn on, need help!

Just recap for now and leave inverter, you can look at inverter and compare it, with the other one, to see if the top shows signs of heat damage, as it looks that way from picture, but you can see more clearly than us,it might be okay with luck, just compare them for now.

[Adasm]

Re: Benq Q9T3 wont turn on, need help!

Alrighty. I'm gonna take this board to a friend and have him help me get new caps to solder in. After that i'll try it and update back here. Thank you both for your help, very much appreciated.

[Wizard]

Re: Benq Q9T3 wont turn on, need help!

Important to have low ESR with high ripple current. If they can't answer your questions at that store, and can read the capacitor markings there, report back with the info before buying these capacitors so we can tell you if it is suitable.

Cheers, Wizard

[sofTest]

Re: Benq Q9T3 wont turn on, need help!

If you can give us also the other markings on the capacitors, we can look up the datasheet for them.

About the transformer, I'm not quite qualified. You could start with measuring the resistance across the various legs, and compare with the same readings on the other transformer. You can also try searching for transformer in the forum. I've seen measuring transformers have been discussed in other threads.

[Bobdee]

Re: Benq Q9T3 wont turn on, need help!

Have you seen this


https://www.badcaps.net/forum/showpo...93&postcount=1

[Adasm]

Re: Benq Q9T3 wont turn on, need help!

k, here's the info:

two biggest caps - Elite
25v1000uF
EL(M)105°C
(B)0312
two medium caps - Elite
16v1000uF
EL(M)105°C
(B)0418
one small cap - Elite
25v470uF
EB(M)105°C
(C)0420

That is every little piece of info off of those caps. So, if you could inform me on which caps to purchase, that would be great. Soldering them in is something I can do easily.
Also, compared the transformers and they look the same. Doesnt seem to me as heat damage, but rather the amber colored protective coating that seems to be on most of the components. But, I could be wrong.
And yes, I did check that topic before, and noticed the badly leaking caps. My transformers look similar to his and he said after replacing the caps all was fine. So, fingers crossed, it's just a cap problem!

[sofTest]

Re: Benq Q9T3 wont turn on, need help!

The Elite EL 25v/1000uF got impedance/ripple 0.021/2360
The Elite EL 16v/1000uF got impedance/ripple 0.023/1820
The Elite EB 25v/470uF doesn't exist according to the datasheet. Max. voltage should be 16 volt. But for other values, they are a little better rated then EL-series.

Anyway, if you can get your hand on Panasonic FMs, they can replace all these capacitors. You can order them from Digikey.com. Also, be sure the check the physical size, especially where components are close.

[Adasm]

Re: Benq Q9T3 wont turn on, need help!

I sized up my caps, but evidently no records match my search criteria.
The 25v/1000uf caps are 13.5mmD x 20mmH 5mm LS
The 16v/1000uf caps are 10mmD x 20mmH 5mm LS
The 25v/470uF caps are 10mmD x 16mmH 5mm LS

I dont know if the lifetime @ temp values or the packaging values matter, but I entered all the sizing info and what not and got nothing.
Also, for the 470uF cap, what do you suggest I can use in it's place if I can't locate a replacement?

[sofTest]

Re: Benq Q9T3 wont turn on, need help!

The point is that the replacements are not bigger. If the sizes you are listing are the old capacitors, you can replace with:
http://search.digikey.com/scripts/Dk...name=P12379-ND
http://search.digikey.com/scripts/Dk...name=P12366-ND
http://search.digikey.com/scripts/Dk...name=P12388-ND

DigiKey seem to be out of stock of the 16v/1000uF Panasonic FM, so if you don't want to wait, the UCC KZE can be used:
http://search.digikey.com/scripts/Dk...me=565-1664-ND

[Adasm]

Re: Benq Q9T3 wont turn on, need help!

ok, im gonna take all this info and see if I can buy these caps and install them tomorrow, will be back for an update tomorrow evening...thanks again for all your help, very appreciated!

[Adasm]

Re: Benq Q9T3 wont turn on, need help!

Well fellas, my hat is off to ya! I replaced the 5 caps and sure enough, i'm using the monitor as we speak! Awesome, can't thank you guys enough!

[tony_5]

Re: Benq Q9T3 wont turn on, need help!

Please have someone from your service manual for LCD monitor Benq Q9T3. My e-mail: tony5@centrum.sk Thank you very much