HannStar Monitor

[momaka]

Re: HannStar Monitor

Multimeter have no standard for the continuity threshold.

Yes, but they do show the voltage drop.

Yep its real low 00.8 from both pads to various areas on the board, the only cap that gave a bit more 10.8 was C515.
What do you sugest replace C513 or pop a few of the others??

Well, if both pads where C513 was show short-circuit to ground, then C513 is likely in parallel with other ceramic capacitors.
The next task is to find all ceramic capacitors that show the same low-reading to ground on both sides. Let me know which ones you find to be like that.

As for C513, you said you measured it at 200k and it still showed no reading (open-circuit), so that means C513 is okay. Save it for right now. You can put it back in the circuit later once we find the faulty component.

[jetadm123]

Re: HannStar Monitor

Yep its real low 00.8 from both pads to various areas on the board, the only cap that gave a bit more 10.8 was C515.
What do you sugest replace C513 or pop a few of the others??

I would suggest you remove C513 from the board and remeasure it's resistance. If it still shows shorted, then replace it.

[rigeback]

Re: HannStar Monitor

Yep its real low 00.8 from both pads to various areas on the board, the only cap that gave a bit more 10.8 was C515.
What do you sugest replace C513 or pop a few of the others??

[retiredcaps]

Re: HannStar Monitor

Low continuity?... How much?

Multimeter have no standard for the continuity threshold. For example, one Fluke multimeter might beep continuity for resistance less than 30 ohms. Another brand I have seen beeps continuity for resistance less than 700 ohms.

[momaka]

Re: HannStar Monitor

I just noticed in your quote its not C13 but C37, sorry about that, one thing with C37 it tests .509 one way and 1.245 opposite!

Yeah, that's usually normal. The reason behind the different readings is because there are diodes in the circuit, and those will read higher resistance/continuity in one direction than in the other.

I removed C513 and tried to test it but no reading even at 200K and no contenuity!

That means C513 is fine.
Outside the circuit, capacitor are indeed supposed to show open-circuit (no continuity at all).

How should I go about testing these caps off board? So far only C513 off board to determin its condition.

Resistance check, just like you were doing it in circuit.
First try 200 Ohm scale... if you get open circuit, go to 2 kOhm scale... if you get open circuit, then the capacitor is more than likely fine and you can put it back in the circuit.

one other thing when probing both sides of the board where C513 was soldered both pads give contenuity to ground???

Low continuity?... How much?
What about resistance - do you get less than 10 Ohms to ground on both sides? If yes, then that's exactly the type of problem we are looking for.

As you can see I need some practice writing QUOTES!!

It's easy. Just type
[*quote* = "name_of_the_person_you're_quoting"]*and place the person's quote here*[*/quote*]
Ignore all of the " * " symbols I put above, though - I only put those there so that the forum will not interpret it as a quote so that you can see the syntax.

[rigeback]

Re: HannStar Monitor

one other thing when probing both sides of the board where C513 was soldered both pads give contenuity to ground???

[rigeback]

Re: HannStar Monitor

I removed C513 and tried to test it but no reading even at 200K and no contenuity! How should I go about testing these caps off board? So far only C513 off board to determin its condition.

[rigeback]

Re: HannStar Monitor

I just noticed in your quote its not C13 but C37, sorry about that, one thing with C37 it tests .509 one way and 1.245 opposite!
As you can see I need some practice writing QUOTES!!

[rigeback]

Re: HannStar Monitor

[QUOTE]: No worries I use to train people and would frustrated as hell some times=momaka;193639]Hi rigeback, sorry if the instructions were a bit confusing. It was pretty late when I typed them last night. Now that I re-read them again, they sound a bit rough with that bald text as if I'm screaming - sorry if you thought they came out that way.

Anyways, back on topic...

Correct


If the "1" is on the left side of the screen of the multimeter, then those capacitors are fine. The "1" on the left side means that the resistance is higher than 200 Ohms (if you're using the 200 Ohm scale) or higher than 2k (if you're using the 2kOhm scale).
We are interested only in the low resistances, so in this circuit, any capacitor that shows above 100 Ohms can be regarded as good.

:No thats okay I did check each cap across although I just noticed in your quote its not C13 but C37, sorry about that, one thing with C37 it tests .509 one way and 1.245 opposite! Except for C13, those other readings are very low. Sorry if I'm asking redundant questions here, but were you checking each of these capacitors accross (that is, one probe on one side and the other probe on the other side of the capacitor)? - If yes, then we have a lot of problems. In that case, start removing those capacitors from the t-con one by one and test them with your multimeter out of circuit. Do they show the same low readings out of circuit on the 200 Ohm scale?


Thanks . Happy Halloween to you as well! (if you are celebrating)
Yes, I'm studying eletronics, but I'm learning more from this forum and from the things I fix than at school .

[QUOTE]:No I'm just taking easy this time round.

[momaka]

Re: HannStar Monitor

Hi Momaka, thanks for the instructions although its nots so easy to comprehend for someone who has never done it before,

Hi rigeback, sorry if the instructions were a bit confusing. It was pretty late when I typed them last night. Now that I re-read them again, they sound a bit rough with that bald text as if I'm screaming - sorry if you thought they came out that way.

Anyways, back on topic...

anyhow took some more readings and you right about the 200 setting that worked for some of the caps.
I take that at this setting of 200 when I get a reading of 00.6 I've got 0.6 Ohms, right? That means I've got a bunch of low readings!

Correct

C523, C524, C505 and C508 and a few more no reading 200 or 2K tester reads 1??

If the "1" is on the left side of the screen of the multimeter, then those capacitors are fine. The "1" on the left side means that the resistance is higher than 200 Ohms (if you're using the 200 Ohm scale) or higher than 2k (if you're using the 2kOhm scale).
We are interested only in the low resistances, so in this circuit, any capacitor that shows above 100 Ohms can be regarded as good.

Anyhow ZZ1 is 00.6, C513 is 00.7, C515 is 10.8, C518 is 00.5 (the Big cap) C13 is 0.502 @2k.

Except for C13, those other readings are very low. Sorry if I'm asking redundant questions here, but were you checking each of these capacitors accross (that is, one probe on one side and the other probe on the other side of the capacitor)? - If yes, then we have a lot of problems. In that case, start removing those capacitors from the t-con one by one and test them with your multimeter out of circuit. Do they show the same low readings out of circuit on the 200 Ohm scale?

Happy halloween and the home work, are you studying electronics?

Thanks . Happy Halloween to you as well! (if you are celebrating)
Yes, I'm studying eletronics, but I'm learning more from this forum and from the things I fix than at school .

[rigeback]

Re: HannStar Monitor

Hi Momaka, thanks for the instructions although its nots so easy to comprehend for someone who has never done it before, anyhow took some more readings and you right about the 200 setting that worked for some of the caps.
I take that at this setting of 200 when I get a reading of 00.6 I've got 0.6 Ohms, right? That means I've got a bunch of low readings!
Anyhow ZZ1 is 00.6, C513 is 00.7, C515 is 10.8, C518 is 00.5 (the Big cap) C13 is 0.502 @2k.
Happy halloween and the home work, are you studying electronics?
C523, C524, C505 and C508 and a few more no reading 200 or 2K tester reads 1??

[momaka]

Re: HannStar Monitor

The drawing in Max 1997 does not give any indication what resistance these caps should be in case I have to replace them?

Capacitors don't have resistance - they will show open-circuit (infinite resistance) when removed from the circuit. The resistance you see in the circuit is the resistance of other components (if the capacitors are good, of course). The only reason to check the resistance of these capacitors here is because when ceramic capacitors go bad, they tend to become short-circuited (i.e. very low resistance).

Which brings me to my next point...

As you said I rechecked all the caps using the manual meter on 200K and it seems C515 is also bad 00.0 Ohms C37 on the other hand is 31.1 Ohms.

Okay, just to clear this up - when you're checking for a short circuit, you use the lowest resistance scale on your multimeter - that is the 200 OHM scale or the 2000 OHM scale (sometimes referred to as 2K Ohm).
The 200K scale is way too high and will always show close to zero misleading you into thinking that a component is shorted when it's not.

The unit of resistance, the Ohm, is a metric unit and thus follows the metric scales. That is:
1000 milliOhms (mOhms) = 1 Ohm = 0.001 kiloOhms (KOhms) = 0.000001 MegaOhms (MOhms).

Resistance is a measure of how hard it is for current to flow through an element. A high resistance (high Ohm value) indicates that very little current will flow. A low resistance (low Ohm value) means it's easy for the current to flow through a component. A short-circuit has very, very low resistance - a fraction of an Ohm usually. Common multimeters cannot measure this low, so they show around 1 or 2 Ohms.

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.

Sorry for not replaying for a few days. Been busy with homework .

[rigeback]

Re: HannStar Monitor

Let me knoe what you're opinion is regarding these caps and how much resistance they should have approximately, can these caps be tested off the board?
Thanks

[rigeback]

Re: HannStar Monitor

Well I'm definitely sure now that ZZ1 and C37 has continuity between the 5V TP and F1 is okay, tested with both testers! C513 seems to connect with VDD+9 on the manual meter as it test diodes on the same setting?
As you said I rechecked all the caps using the manual meter on 200K and it seems C515 is also bad 00.0 Ohms C37 on the other hand is 31.1 Ohms.
The drawing in Max 1997 does not give any indication what resistance these caps should be in case I have to replace them?

[momaka]

Re: HannStar Monitor

Yes C532 is connected to VDD+9V C37 and ZZ1 are connected to the 5v rail.
These caps have very low resistances like 00.1 and 000 (C513/ZZ1/C508) but there again the resistance levels are so low that I can only use the auto tester.

Which test point are these caps connected to?
If the resistance is very low, it shouldn't matter whether you use the manual or the auto meter. The manual multimeter should show no more than 2-3 Ohms when you short its probes. The fact that you get different results with the two multimeters means you're probably not measuring something right.
If I can see this correctly, cap ZZ1 is connected between ground and the 5v rail. You said in one of your earlier posts that the 5v rail is not shorted to ground. Yet, cap ZZ1 is shorted? For that to happen, either fuse F1 must be bad again or your auto meter isn't measuring properly.

Let me know if you think I should change these out as I think I have some the same on a scrap MB or should I hook up the 5 Volts and where would the best place be to do that?

In this case, I think you should recheck the above caps with the manual meter. 200 or 2000 Ohm scale. A shorted cap will show no more than 2 to 3 Ohms resistance. A bad cap can show as much 30 Ohms, but not more.

[rigeback]

Re: HannStar Monitor

Yes C532 is connected to VDD+9V C37 and ZZ1 are connected to the 5v rail.
These caps have very low resistances like 00.1 and 000 (C513/ZZ1/C508) but there again the resistance levels are so low that I can only use the auto tester. Let me know if you think I should change these out as I think I have some the same on a scrap MB or should I hook up the 5 Volts and where would the best place be to do that?

[momaka]

Re: HannStar Monitor

VDD +9 also connects with C521 right next to the Max97, the resistance of this cap might be suspect 15.97/119.6?

It's fine. If it's bad, you'd see the same low resistance in both directions (i.e. regardless of which way you have the probes).

C521 then connects with C37 and ZZ1 resistance seems normal on these caps. From C37 connects to C532 and Q505.

Many of the big caps are connected to ground on one side. I hope you're not measuring the common grounds between those items, because these measurements are confusing me a lot. C37 and ZZ1 are connected to the 5v rail if I'm not mistaken, while C532 likely is connected to VDD+9V, correct?

Would it be wise to try reflowing the solder on all the caps with flux, or testing every cap within Max97 area?

The reflowing won't do anything, I'm pretty sure.
Checking the resistance of the caps around the MAX1997 is a good idea though. In fact, check all of the large ceramic caps on the t-con.

I notice there is another TPVDD+ next to the C42 but it does not connect to the VDD+9 point?

I'm not sure what that is either - perhaps it connects to something else. Probably don't need to worry about it now.

[rigeback]

Re: HannStar Monitor

VDD +9 also connects with C521 right next to the Max97, the resistance of this cap might be suspect 15.97/119.6? C521 then connects with C37 and ZZ1 resistance seems normal on these caps. From C37 connects to C532 and Q505.
Would it be wise to try reflowing the solder on all the caps with flux, or testing every cap within Max97 area?
I notice there is another TPVDD+ next to the C42 but it does not connect to the VDD+9 point?

[rigeback]

Re: HannStar Monitor

Just checked the risistance with the auto tester and I get 1493 between F1 and Pin 29, with manual tester only get a reading on 2M so must be real low. VDDA is just right of F1 looking from the top of the T-con next to L1.

[momaka]

Re: HannStar Monitor

Hi Momaka, R522 (19.6 Ohms) is not connected to F1 however its connected on one side to Pin 29 and the otherside to Pin 30 and also to R57 (00.1 Ohms) near F1, R522 is marked with 900 or 90B hard to see. R57 is connected to a bunch of parts around the main hannstar chip like C1/C4/C18/C19 etc.

Interesting, but it still doesn't make too much sense to me.
I guess one last thing to try before we apply 5v to pin 29... what is the resistance between pin 29 of MAX1997 and fuse F1?

I noticed today theres another test point called VDDA which is hooked up with Q502 centre pin.

Probably supplies power to IC1. I can't seem to locate VDDA, though. Do you know where should be looking?