HannStar Monitor

[PlainBill]

Re: HannStar Monitor

It gets worse, today I wanted remove the screen from its housing and while doing so one of the caps fell behind the ribbon connectors, as I lifted out the screen 2 of the ribbon connectors came off!
I'm not sure how well they were attached to t-con board in the first place but they sure came off easy and makes me think because these 2 connectors are also the ones with lines during start up.
Next question, how are these ribbons connected to the t-con board, maybe with glue or solder?????

It's a special adhesive. At this point the LCD panel and TCON are useless - or perhaps I should say nobody has reported successfully repairing a failure of the bond on these cables.

PlainBill

[rigeback]

Re: HannStar Monitor

It gets worse, today I wanted remove the screen from its housing and while doing so one of the caps fell behind the ribbon connectors, as I lifted out the screen 2 of the ribbon connectors came off!
I'm not sure how well they were attached to t-con board in the first place but they sure came off easy and makes me think because these 2 connectors are also the ones with lines during start up.
Next question, how are these ribbons connected to the t-con board, maybe with glue or solder?????

[PlainBill]

Re: HannStar Monitor

Yes I am sure there is a short in the MAX 1997 between DRVP (Pin 22) FBP (Pin 21) and FB (Pin 20) it seems the solder is connecting possibly due to my probing, I tried cleanning the spaces between the joints but still have contenuity, or are these pins connected together externally??
The bad caps in one case are in sequence C268 through C270

A short between pins 20, 21, and 22 could be an internal short of the MAX1997.

PlainBill

[rigeback]

Re: HannStar Monitor

Yes I am sure there is a short in the MAX 1997 between DRVP (Pin 22) FBP (Pin 21) and FB (Pin 20) it seems the solder is connecting possibly due to my probing, I tried cleanning the spaces between the joints but still have contenuity, or are these pins connected together externally??
The bad caps in one case are in sequence C268 through C270

[PlainBill]

Re: HannStar Monitor

Well I've found more than 10 caps that are giving this 00.8 & 12.2 Ohms reading which seems to start at the VCOM VCOM_1 area, in the MAX1997 area only 2 caps are reporting the same measurement C515 and C513 which were already removed and tested OK.
Surely it would be impossible that all these caps are bad and the main cause is the MAX1997????

Probably only one cap is bad. If they are decoupling caps they are in parallel, just like the first picture. And yes, it is possible the problem is the MAX1997.

PlainBill

[rigeback]

Re: HannStar Monitor

Well I've found more than 10 caps that are giving this 00.8 & 12.2 Ohms reading which seems to start at the VCOM VCOM_1 area, in the MAX1997 area only 2 caps are reporting the same measurement C515 and C513 which were already removed and tested OK.
Surely it would be impossible that all these caps are bad and the main cause is the MAX1997????

[PlainBill]

Re: HannStar Monitor

So I remeved C254 cap with the 1.2 Ohms and this cap seems fine, again when I probe the contact points on the board of cap I get the same low reading, is it the source of this area that is faulty or all the cap in the area?

It could be any component that is connected to these two points. I've attached a couple of pictures as an illustration. The first is the capacitor network on the 3.3V power rail of the signal (logic) card in an Acer monitor. Note that a low resistance measurement across a capacitor shown could be caused by ANY capacitor shown. The second picture shows the traces connecting all of the mounting points - this happens to be part of the power supply from a Viewsonic monitor. Note that while some traces are short, others wander over a wide area.

PlainBill

[rigeback]

Re: HannStar Monitor

So I remeved C254 cap with the 1.2 Ohms and this cap seems fine, again when I probe the contact points on the board of cap I get the same low reading, is it the source of this area that is faulty or all the cap in the area?

[rigeback]

Re: HannStar Monitor

I got to admit my last question was a bit dumb, excuse me.
I went over an area today that I have been neglecting which is in fact should be the area of interest is probably the most important, directly above the dark lines in the screen during start up, the of the t-con near the side. I have been testing too much in the Max1997 area which is probably okay.
I also went back and reread what Momaka had said: "With that said, my original question was, do any of the above capacitors show a very low resistance across? And by very low, I mean less than 30 Ohms".
Well infact I did find a few caps that are measuring 1.2 Ohms and 0.6 Ohms today testing with the 200 setting.
I will change these out and try powering up again!
Many thanks for the precise imformation.

[retiredcaps]

Re: HannStar Monitor

One other question regarding using a multimeter correctly, does one hold the probes until the numbers stop counting "like I have doing" or is it the first numbers on the screen that give the correct reading, just to be certain before I shelve this project.

A good multimeter will accurately display the unit of measurement quickly without any "overshoot" or "undershoot". That is, if the correct voltage is 3.3V DC, a good multimeter will show 0.0V (because you the probes are not in place yet) and then 3.3V quickly.

A poor one will display 4.1 (overshoot), 2.9 (undershoot), and then settle on 3.3V DC.

Some components when being measured will react or be influenced by the multimeter so the readings will take a few seconds to stabilze.

[rigeback]

Re: HannStar Monitor

5) If you think your multimeter is not working when reading resistance, do a real simple test. Put your multimeter on 200 ohms and touch your probes together. It should read less than 1.0 ohms. Any reading above 1.0 ohms when your probes are touching suggests a bad/weak battery or your test leads are worn (wires inside are fraying).

One other question regarding using a multimeter correctly, does one hold the probes until the numbers stop counting "like I have doing" or is it the first numbers on the screen that give the correct reading, just to be certain before I shelve this project.

[rigeback]

Re: HannStar Monitor

5) If you think your multimeter is not working when reading resistance, do a real simple test. Put your multimeter on 200 ohms and touch your probes together. It should read less than 1.0 ohms. Any reading above 1.0 ohms when your probes are touching suggests a bad/weak battery or your test leads are worn (wires inside are fraying).

Thanks for that information and I have just checked my multimeter as you said and it reads 00.5 Ohms which suggests its okay.

[rigeback]

Re: HannStar Monitor

I appologize for not indicating 1.145 Ohms I was taking it for granted I guess that any one reading would understand but you're right.
Thing is with this T-con when testing with the 200 Ohms setting it gives an overall "1" and 00.5 reading when testing the caps, so I don't think if I will ever find the short to get it going!

[retiredcaps]

Re: HannStar Monitor

5) If you think your multimeter is not working when reading resistance, do a real simple test. Put your multimeter on 200 ohms and touch your probes together. It should read less than 1.0 ohms. Any reading above 1.0 ohms when your probes are touching suggests a bad/weak battery or your test leads are worn (wires inside are fraying).

[retiredcaps]

Re: HannStar Monitor

but its real confusing how to determin whats shorted as there is no reading across even on 2M and no conteuity

I have been reading along and suggest you consider the following. With respect, I think you misunderstand how to use a multimeter and what we are asking for when looking for a shorted component.

1) A multimeter always gives a reading. "1" on the left hand side of the display means the reading is "out of range". 1.0 on the right side on the display is a unit of measure (i.e. 1 unit of measure). As you as you turn on the multimeter, it gives you a reading. There is no such thing as "no reading".

2) When testing for a short, put your multimeter on 200 (two hundred) ohms. Any reading under 30 ohms suggests a short. If your multimeter reads "1" on the left hand side, it is telling you that the resistance is greater than 200 ohms (out of range for the dial setting). At this point, we don't care what the actual resistance reading is. We know it is NOT less than 30 ohms and thus it is NOT shorted.

So testing for a short on the 2K, 20K, or 2M dial setting is pointless. In fact, testing for a short on the 2M can lead to misdiagnosis.

3) For beginners, using an autoranging multimeter is much easier. You don't have to worry about dial settings, etc.

4) When reporting measurments, we need to know what you have recorded. 1.0 means nothing. Is it 1.0 ohms, 1.0V DC, 1.0V AC, 1.0uF, etc?

[rigeback]

Re: HannStar Monitor

Well it turns out that I retested C1 and got a reading 1.145 /.000 and C15 next door gives the same so I left them alone.
Anyways I checked the group of caps C507, C508 and C509 and they had some low values 1. /.000 so I removed C509 but its real confusing how to determin whats shorted as there is no reading across even on 2M and no conteuity so I'm lost for ideas now??
C510 has a slightly different reading to the other caps in the group 1.872 but probably OK I guess!

[momaka]

Re: HannStar Monitor

Thanks for the explanation PlainBill. Makes it much easier for me to explain as well .

@rigeback:
yes, remove C1, and test out of circuit.

[rigeback]

Re: HannStar Monitor

Bill thanks for the help outlining them items on the picture, that really makes a lot more easy to understand, I guess I miss the point here without realizing it, yes C1 in this case will be a main suspect.

[PlainBill]

Re: HannStar Monitor

Okay, new tests to ground indicate that most of the "C" caps are okay, however 7 of the "R" caps / diodes test .500 both ways, these are the small black caps with (000) or (010) markings?
ZZ1 is also .500 both ways and L1/2/3 check 1.140 both ways and C1 is .000 both ways.
All tests were done at 2K, the black caps mostly indicate through contenuity!

I've been stayong out of this thread, momaka has been doing much better than I could, but I saw something that really needs correction. This post indicates one of the reasons there has been so many difficulties troubleshooting.

A component whose identifier starts with an R is a resistor, not a capacitor. an identifier that starts with C is a capacitor, D is for Diode, Q for Transistor, L for inductor. I've marked up some or them on the picture.

I wasn't able to locate C1, but that reading indicates it is a prime suspect.

PlainBill

[rigeback]

Re: HannStar Monitor

Okay, new tests to ground indicate that most of the "C" caps are okay, however 7 of the "R" caps / diodes test .500 both ways, these are the small black caps with (000) or (010) markings?
ZZ1 is also .500 both ways and L1/2/3 check 1.140 both ways and C1 is .000 both ways.
All tests were done at 2K, the black caps mostly indicate through contenuity!