HannStar Monitor

[rigeback]

Re: HannStar Monitor

Powered it up today and 5.3V is on the T-con but no 9 Volts on VDD+9V does this mean MAX1997 chip has a problem?

[PlainBill]

Re: HannStar Monitor

Possibly. Or there is a bad solder joint.

PlainBill

[rigeback]

Re: HannStar Monitor

Tried it out with power but still no 9 volts on VDD+9V, 5,3 volts is on the t-con although all test points VGH, VGC and VGL are 0 volts, dose this mean MAX1997 is bad, that will be hard to find and install! sorry didn't notice we were on page 4, okay Bill will have a look as I did notice the solder points of MAX1997 might be connecting causing this short.

[momaka]

Re: HannStar Monitor

I doubt the MAX1997 IC is bad (although it could be). More often than not, it's other components (particularly ceramic caps and diodes) that go bad.

Since you did have 9.5v on VDD+9V before, we have to start from the beginning again...

So, check fuse F1 again. If it's still good (i.e. shows continuity), then see if anything on the t-con gets hot when you power it on. You might have to cycle the power on and off a few times to determine this since the MAX1997 has overload protections and may cut power if it detects one.

If nothing gets hot, check voltage on pin 29 (IN) and pin 30 (ONDC) - they should both be 5.3v or close.

Also, I think D507 should be the VDD+9V rectifying diode, but I'm not quite sure, so check if one side of D507 shows low continuity to VDD+9V. If yes, check D507 for continuity both ways. One way should show lower continuity than the other.

[rigeback]

Re: HannStar Monitor

Tried cycling the power to see if anything gets hot but seems normal to me or I'm not sensitive enough!
With 5.5 volts on the T-con Pin 29 IN is 629 MV and that was achieved with the small auto tester. Pin 30 ONDC is 4.14Volts.
As for the contenuity between VDD+9 and D507 I get 16.20 and 10.29 on each pin. I took a power reading as well on the same and got 4.88V and
5.07V

[momaka]

Re: HannStar Monitor

With 5.5 volts on the T-con Pin 29 IN is 629 MV and that was achieved with the small auto tester.

Well, pin 29 (IN) is what gives power to the MAX1997 IC - without it, the MAX1997 can't turn on. There needs to be at least 2.7 present on that pin for the MAX1997 to start.
According to the sample circuit in the MAX1997 datasheet, Pin 29 and Pin 30 should be tied together, so you should see the same voltage on each.
Can you get short-circuit continuity between pins 29 and 30? If so, then they are connected. If not, there should be a resistor between Pin 29 and the 5v rail -find that resistor on your t-con and test it. Its resistance should show no more than 5% over its printed value on top. The sample circuit in the data sheet on page 13 calls it R1.

As for the contenuity between VDD+9 and D507 I get 16.20 and 10.29 on each pin. I took a power reading as well on the same and got 4.88V and
5.07V

Those continuity readings tell me that D507 is not the rectifying diode for VDD+9V, but the voltage measurements tell me otherwise. Not quite sure what's happening here. Try measuring the resistance (using lowest resistance setting on your multimeter) between VDD+9V and both sides on D507. Any of these show a really low resistance (less than 2 Ohms)?

[rigeback]

Re: HannStar Monitor

R524 connects with pin 29 and has a resistance of 300 ohms its marked with (54D) it also connects with Q503 on pin 2.
I can't get a short circut between pin 29 & 30 or over to R1 as shown in the data sheet.
VDD+9 to D507 gives 9.60 and 110.9, do you think its possible that R524 or Q503 is the culprit?

[momaka]

Re: HannStar Monitor

VDD+9 to D507 gives 9.60 and 110.9

Well, perhaps D507 isn't the rectifying diode for VDD+9V then.
The only other diode that could be the rectifying diode for VDD+9V is D505. Does D505 connect to VDD+9V on one side and the inductor L501 (the big one with "4R7" on top)?

R524 connects with pin 29 and has a resistance of 300 ohms its marked with (54D) it also connects with Q503 on pin 2.

Is one side of R524 or pin 2 of Q503 connected to fuse F1 by any chance?
According to the sample circuit, that's how it should be, unless this t-con was designed differently.
Also, are you sure R524 is not marked as 540? Because in that case, the resistance of R524 should be 54 Ohms (56 Ohms at the most), which I think is still fairly reasonable considering that the sample circuit suggests a value of 10 Ohms.
I'm also not sure what 54D would mean for a resistor. It could be that R524 is bad (too high in value), but I can't confirm that. Either way, don't remove/replace it yet.

I can't get a short circut between pin 29 & 30 or over to R1 as shown in the data sheet.

R1 on your t-con is different from R1 in the data sheet.
From the pictures, it seems that pin 29 & 30 are indeed not connected together. Perhaps, that's how your t-con was designed to be. In any case, there needs to be at least 2.7 volts on pin 29 (IN) in order for the MAX1997 to work at all.

If you feel adventurous, connect a 5 volt source to pin 29 through a 10 to 20 Ohm resistor and see if VDD+9V comes up. But again, that's only if you feel adventurous, since this may cause damage to your t-con. In all honesty, this t-con is getting over my head as normally most t-cons I've seen closely resemble the sample circuit for their ICs. But this one just doesn't seem to be that way. I hope you're not getting too frustrated with it (or me) .

[rigeback]

Re: HannStar Monitor

Hi Momaka, I thought this one was going to be a pain in the butt when I saw it!
I started from VDD+9 searching for contenuity and I landed on L301 which has contenuity accross (00.1 ohms) and from the opposite side led me to C531 (757 Ohms) and also C532 then it goes to D505 and on the same pin to C504 and R522, the opposite pin of D505 goes to pin D506 pin 1 which makes me think its the rectifier? From D506 testing on all pins I cannot find a source. R522 goes to IN pin 29.
R524 and Q503 do not connect to fuse F1.
I don't mind connecting a 5 volt source and even if it blows I'll keep th erest for spares, hopefully I am not frustrating you or anyone, for me its just an interesting hobby when there is spare time.

[momaka]

Re: HannStar Monitor

R522 goes to IN pin 29.

Okay, does R522 connect to fuse F1 then? From what I can see, R522 has "000" printed on top, is that correct?
If R522 does not connect to fuse F1, then trace what else it connects to. The MAX1997 needs to get its power from somewhere and that's of primary concern right now.

hopefully I am not frustrating you or anyone, for me its just an interesting hobby when there is spare time.

No, not at all. For me it's a hobby as well and I usually keep going until I exhaust all ideas.

[rigeback]

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.
Testing contenuity from Pin 30 connects with Q503 Pin 1, Q503 Pin 2 goes to VGH and Pin 3 to R515.
I noticed today theres another test point called VDDA which is hooked up with Q502 centre pin.

[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?

[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.

[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?

[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

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

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

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?

[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

[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 .