Acer 1716B no picture, Blinking power light

[nico95]

Hi,
I have a Acer 1716B LCD monitor. It was working fine and then one day no picture, just black. No backlight from what I could tell. The power light blinks green. I took it apart and didn't see any bad caps. I also took a ESR meter and tested them all. I didn't come across any with high ESR. All seemed to be in range or rather close. My meter tests in circuit and also tests Capacitance. I know many times it tests High capacitance in circuit but I don't think the Caps are a problem at this point capacitance wise. I think they would be much lower if they where in circuit, but obviously it is possible. Nothing is bulging or leaking. Everything I ran across on line pointed to bulging caps. Any and all help is greatly appreciated. I would really like to get this monitor going if possible. Reasonably.
Thanks,
Nick

[PlainBill]

Re: Acer 1716B no picture, Blinking power light

Hi,
I have a Acer 1716B LCD monitor. It was working fine and then one day no picture, just black. No backlight from what I could tell. The power light blinks green. I took it apart and didn't see any bad caps. I also took a ESR meter and tested them all. I didn't come across any with high ESR. All seemed to be in range or rather close. My meter tests in circuit and also tests Capacitance. I know many times it tests High capacitance in circuit but I don't think the Caps are a problem at this point capacitance wise. I think they would be much lower if they where in circuit, but obviously it is possible. Nothing is bulging or leaking. Everything I ran across on line pointed to bulging caps. Any and all help is greatly appreciated. I would really like to get this monitor going if possible. Reasonably.
Thanks,
Nick

Oh Crystal Ball, can you show me this monitor? Nope, it's not helping today.

Guess you are going to have to do this the easy way. Take an overall picture of the power supply board and attach it to your reply. Follow the link in my signature for the procedure.

Some models of Acer monitors were notorious for shorted inverter transistors.

PlainBill

[nico95]

Re: Acer 1716B no picture, Blinking power light

Thanks PlainBill, sorry I forgot about a pic
I just attached it. I can take closeup if needed.
Thanks,

Nick

[retiredcaps]

Re: Acer 1716B no picture, Blinking power light

Check the two transistors flanking C221 (grey square cap) to make sure they are not shorted.

What part number are those two?

[retiredcaps]

Re: Acer 1716B no picture, Blinking power light

Can you also post a pic of the underside? The J921 area looks a bit discolored from something on the underside?

[nico95]

Re: Acer 1716B no picture, Blinking power light

They each says KDY on the left side going veritically. In the middle is 1691 and then below that there is a 603. Im guessing they are 1691? I have a dumb question. I have never been good or figured out how to test a Transister especially for a short. I don't believe my meter says short on the diode mode. They are a BCE package. any help with testingwise would be appreciated. Sorry Im still learning some some stuff.
Thanks,
Nick

[nico95]

Re: Acer 1716B no picture, Blinking power light

I just posted a pic of the backside. I hope that helps.
Thanks

[retiredcaps]

Re: Acer 1716B no picture, Blinking power light

Sorry Im still learning some some stuff.

No worries. I just learned this stuff too.

Number the pins 1,2,3.

With power off and your LCD unplugged. Set your multimeter to 200 ohm if it is manual. Black probe in com and red probe in ohm.

1) put black probe on pin 1, red on pin 2 - record ohm
2) put black probe on pin 1, red on pin 3 - record ohm
3) put black probe on pin 2, red on pin 3 - record ohm

If any of the readings are less than 10 ohm, you probably have a short. To confirm, you will have to desolder them and test them out of circuit.

Additionally, you can do a diode test the same way. Put your multimeter on diode test.

1) put black probe on pin 1, red on pin 2 - record diode measurement
2) put black probe on pin 1, red on pin 3 - record diode measurement
3) put black probe on pin 2, red on pin 3 - record diode measurement
4) put red probe on pin 1, black on pin 2 - record diode measurement
5) put red probe on pin 1, black on pin 3 - record diode measurement
6) put red probe on pin 2, black on pin 3 - record diode measurement

A good diode should read between 0.4 and 0.7. In the other direction it should read 0L.

List all your meaurements and we can confirm.

edit: 1691 is the correct identifier. Datasheet is at

http://pdf1.alldatasheet.com/datashe...D/KSD1691.html

[nico95]

Re: Acer 1716B no picture, Blinking power light

Thanks for the testing info!
I did the OHMS test and 1-3(B-E) is about 1.3-6 on both Transistors and around 15-17 fpr 1-2 & 2-3 on both. I didn't try the diode test yet since the one wasso low. I will unsolder them tommorow and then let you know(do both tests) I would like to unsolder tonight but running out of time.
Thanks again, and I will let you know tommorow.

[retiredcaps]

Re: Acer 1716B no picture, Blinking power light

Thanks for the testing info!
I did the OHMS test and 1-3(B-E) is about 1.3-6 on both Transistors and around 15-17 fpr 1-2 & 2-3 on both.

Anything 3 legged and starts with a Q on your board can also be tested in the same way to make sure they are not shorted.

If you are getting 1.3 ohms, it is likely shorted.

Once removed, retest and report back.

[nico95]

Re: Acer 1716B no picture, Blinking power light

Hi Sorry,
I just got to do this sorry it took so long. I took out those 2 and tested out of circuit the first one was as follows

1-2 38
1-3 225
2-3 258

Second

1-2 25
1-3 1.3
2-3 29

Looks like the second one is shorted?
I tested all the others in circuit and they all where above 10 accept.
what looked like to voltage regualtors(they where labled D921 and D 922)
the 1-3 on both where 1.3. IS that something I should test out of circuit or something I need to test differentlly. Those are connected to the large heat sink what looks like the secondary side. I also noticed what looked like cold soldier joints. A lot of them. Can't tell if you can see them in the pic. Should I touch those up? Im guessing it can't hurt. one is on the large filter capacitor. and on the primary second voltage regulator. Again sorry for the delay in getting back. I haven't been able to get to this until tonight.
Thanks,
Nick

Anything 3 legged and starts with a Q on your board can also be tested in the same way to make sure they are not shorted.

If you are getting 1.3 ohms, it is likely shorted.

Once removed, retest and report back.

[retiredcaps]

Re: Acer 1716B no picture, Blinking power light

Hi Sorry,
I took out those 2 and tested out of circuit the first one was as follows

1-2 38
1-3 225
2-3 258

Second

1-2 25
1-3 1.3
2-3 29

Looks like the second one is shorted?

1.3 ohm is definitely shorted. I would also say 38 ohms is shorted so both are shorted. Out of circuit, both transistors should measure well over 1000 ohms.

I tested all the others in circuit and they all where above 10 accept.
what looked like to voltage regualtors(they where labled D921 and D 922)

D is usually for diode. Voltage regulators are "U".

You can test voltage regulators for shorts by (power off and unplugged)

black on pin 1- red on pin 2 - record ohms
black on pin 1- red on pin 3 - record ohms
black on pin 2- red on pin 3 - record ohms

Diodes can be tested with the diode checker on your multimeter. Put black on one side, red on the other. Record. Reverse probes. Record. One should read 0.4 to 0.7. The other should read 0L.

I also noticed what looked like cold soldier joints. A lot of them. Can't tell if you can see them in the pic. Should I touch those up?

You must resolder the all the transformer pins and anything that looks like a bad solder joint. It is likely the poor solder joints on the transformer pins caused the transistors to short out.

[nico95]

Re: Acer 1716B no picture, Blinking power light

Thank!,
I finally got another few mintues to get back to this. I really want to get his going and greatlly appreciate your help and paitience

I will replace both of those transistors, but I will wait to get them till I make sure I don't anything else. I fixed a bunch of the cold solder joints. Ther are sure enough of them. Looks like its anothing that needs a lot of heat. Must be there equipment couldn't keep up.
Those Diodes are three pin instead of 2. How do I test these. Each is a different Part#

First is W1256 below that is 6417 the second is N 6B below that is
FCH10U15 the nbelow that is 161.
I wasn't sure how to test them next and if I should test them 1-2 and 2-3 swaping sides 2-1 3-2? I have them both out of circuit. Wasn't sure If I needed to, but thought It would be a good idea to get a accurate reading.

I tested the other 4 transistors on the board. 2 Small regular transistors and 2 voltage regulator looking transistors All 4 tested "1" on 200 ohms so they where all over 200 OHms. Do I need to test them all out of circuit or should that be good.
Thanks,
Nick

[retiredcaps]

Re: Acer 1716B no picture, Blinking power light

I fixed a bunch of the cold solder joints. Ther are sure enough of them. Looks like its anothing that needs a lot of heat. Must be there equipment couldn't keep up.

Any board with RoHS probably uses lead free solder. It is tougher to remove that your 60/40 solder. Using 60/40 with rosin core helps.

Those Diodes are three pin instead of 2. How do I test these. Each is a different Part#

First is W1256 below that is 6417 the second is N 6B below that is
FCH10U15 the nbelow that is 161.

Sorry, where are these on the board? I can't see them. Can I get pictures of these?

I tested the other 4 transistors on the board. 2 Small regular transistors and 2 voltage regulator looking transistors All 4 tested "1" on 200 ohms so they where all over 200 OHms. Do I need to test them all out of circuit or should that be good.

Those 4 transistors should be good.

[nico95]

Re: Acer 1716B no picture, Blinking power light

"Any board with RoHS probably uses lead free solder. It is tougher to remove that your 60/40 solder. Using 60/40 with rosin core helps."

That would explain why it's been taking so long then I thought that seemed a little odd

"Sorry, where are these on the board? I can't see them. Can I get pictures of these?"

I just attached pics of where they are located and pic of the Transistors out of the board(best pic I could get)

"Those 4 transistors should be good".

I'm glad I should have to worry about those other 4 Tranistors

[jetadm123]

Re: Acer 1716B no picture, Blinking power light

I will replace both of those transistors, but I will wait to get them till I make sure I don't anything else.

Smart move to test other components prior to ordering parts. Even if you looked at and tested the caps, if they're made by Capxon, Elite or one of the other known "bad" manufacturers, why not go ahead and replace them all (with the exception of the large one)? Panasonic FM low-esr caps are relatively cheap and will save you the hassle of having to open up your monitor again. Hint: (remember the name of this forum?)

[retiredcaps]

Re: Acer 1716B no picture, Blinking power light

I just attached pics of where they are located and pic of the Transistors out of the board(best pic I could get)

Pictures always help a lot. From your pics, I can tell they are dual diodes (I think that is the correct term).

As you can see in the pic, the direction of the diodes both point towards pin 2.

Set your multimeter on diode test function.

So put your black probe on pin 2, red probe on pin 1 and you should get some reading like 0.4 to 0.7 in this direction. Then black on pin 1 and red on pin 2 and you should get 0L.

Next test is black probe on pin 2, red probe on pin 3 and you should get some reading like 0.4 to 0.7 in this direction. Then black on pin 3 and red on pin 2 and you should get 0L.

[nico95]

Re: Acer 1716B no picture, Blinking power light

Thats a real good point about the pics. I will try and remember to take pics ahead time next time.

I do see the little pic. That makes a little more sense now. Although I have never seen one of these before
The W2156 tests 1-2 160 3-2 160 and 1 in the other direction for both. I unfortunatlly don't have 0l on my meter. Iwish it was 0l instead of 1! makes it a little less confusing.
The other one N 6b is 1-2 236 3-2 236 and 1 in the other direction for both.

Does that mean there both good since there not open or shorted. Just a little higher reading maybe normal?

[nico95]

Re: Acer 1716B no picture, Blinking power light

Thanks for pointing out about the Caps Jetadm123.
I should probably repalce them they are Elite Caps.
I will start getting the info and look them up and see what I can find. Im glad you pointed that out. Since it should be that much for the caps. If some parts already went the Caps will probablly next. Since that seems common anyways.
Thanks!
Nick

[retiredcaps]

Re: Acer 1716B no picture, Blinking power light

The W2156 tests 1-2 160 3-2 160 and 1 in the other direction for both.

Does that mean there both good since there not open or shorted. Just a little higher reading maybe normal?

I can't find a spec sheet for W2156, so let's assume they are good. If your monitor doesn't work after changing out those shorted transistors, we can relook at these dual diodes.