HannStar Monitor

[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

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, 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

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

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

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

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

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 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.

[PlainBill]

Re: HannStar Monitor

Possibly. Or there is a bad solder joint.

PlainBill

[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?

[rigeback]

Re: HannStar Monitor

Put a new 2A fuse on and took some resistance readings VGH-371 ohms, VGL-99.5 ohms and VGC-505 ohms. VDD+9V -770 ohms.
DRVN/DRVP still the same, the oly thing I can think of is I am in the wrong orientation which would assume the test locations are okay, I am afraid that it will blow the fuse when I do power it up but see tomorrow.

[momaka]

Re: HannStar Monitor

Sorry but please confirm for me that F1 is the part just below the TP looking form the top of the monitor.

Correct.
The fuse is the little part with the "ND" marks on top. Not sure what the "ND" stands for, though. Usually it's only 1 letter. Going by the first letter, "N", this fuse would be rated for 2.0 Amps. Going by the second letter, "D", the fuse would be 0.25A.
Most t-con boards use between 0.5A to 1.5A, so the fuse on your t-con is most likely rated for 2.0A.

D505, c523 and C524 all have contenuity on one point.

That's good. Looking at the picture you provided, D505, C523, and C524 should indeed be connected to ground on one side.

I'm afraid that both DRVN/DRVP have contenuity to ground

This has me stumped, because the MAX1997 data sheet does not provide internal block diagrams of the positive and negative regulator circuits in the chip. I'm guessing that the MAX1997 IC produces the DRVP and DRVN signals with MOSFETs. If this is the case, the only way both DRVN and DRVP could short to ground is if both MOSFETs for DRVN and DRVP are shorted, which is very unlikely.

At this point, I would say just replace fuse F1 with a 2.0A fuse (1.5A might work too if you don't have 2.0A) and see what happens.
Make sure to keep measuring the voltage on VDD+9V before and after you turn on the monitor. VDD+9V should come up to 9V or so within a few seconds. If it doesn't come up within 5 seconds, turn the monitor off, and check fuse F1 again.

If you don't have any SMT fuses, but you do have alligator clips and a regular type fuse, you can use that instead. You can also use an external 5v power supply (such as a PC PSU) instead of the monitors power supply if this makes it easier for you to hook up the regular fuse.

In any case, do NOT replace the fuse with a wire. I've worked on one monitor where the fuse didn't blow as it should have when the t-con shorted, and as a result, a small transistor on the video/logic board also burned. I did end up fixing the monitor, but the fix wasn't proper because I didn't know the specs of the transistor that burned so I couldn't get a new one.

[rigeback]

Re: HannStar Monitor

The little black F1 fuse has an ID "ND" but voltage indicated.

[rigeback]

Re: HannStar Monitor

Sorry but please confirm for me that F1 is the part just below the TP looking form the top of the monitor, I was thinking it was C37 next to ZZ1 & ZZ1TP, even so the contenuity remains the same one end connects to the TP and nothing else.
I'm afraid that both DRVN/DRVP have contenuity to ground, D505, c523 and C524 all have contenuity on one point.
VDD+9V 08.3 @ 200K
I'll start looking for a fuse but not sure what to replace it with, got a scrap Mobo that might ahve it onboard!

[momaka]

Re: HannStar Monitor

No I cannot get a contenuity signal across F1 which I assume is that realy small SMT.

That means F1 is bad.

No I cannot get a contenuity signal between ground and VDD+9V.

Good.
VDD+9V should have about 100 to 500 Ohms or so resistance, so that's fine.

Yes I am afraid there is contenuity between DRVN and DRVP

That's not good.
Check continuity between ground and DRVN/DRVP.

Also check D505, as well as C523 and C524 (I think C523 and C524 should be in parallel).

[rigeback]

Re: HannStar Monitor

Regarding the Maxim chip orientation I am assuming that the printing on the chip is the same reference as in the pfd page 30, top side towards the top of the screen.
If this is true 9-DRVN is with D501 0n Pin 3 and also connecting with D505.

[rigeback]

Re: HannStar Monitor

Yes there is 5.3 Volts on the TP next to F1.
No I cannot get a contenuity signal across F1 which I assume is that realy small SMT.
No I cannot get a contenuity signal between ground and VDD+9V.
Yes I am refering to the drawing https://www.badcaps.net/forum/attachm...1&d=1294381123 for the pin outs.
Yes I am afraid there is contenuity between DRVN and DRVP, I am using the pin configurations listed in the pdf for the orientation. I might have caused a short here while pressing the probes for the tester.

[momaka]

Re: HannStar Monitor

As you said I tested the contenuity on the individual rails etc but to have more room I removed the power / video panel. Anyway I decieded to go through the power check afterwards starting at VDD+9 Volts and there was nothing, so I checked the incoming power at TP and there is the 5.3 Volts but when I check F1 I get nothing on both sides??

Not possible.
There should be 5.3V at least on one side of F1 (the one that is connected to TP_5V).

Some thing is real strange here because when I unpluged the board and checked the contenuity from F1 out going and on board I get a signal.

???
Not sure what you mean here with "get a signal". Is there continuity across F1 or not?

If no, then back to where you started - check continuity between VDD+9V and ground.

3-DRV1 is Q502 on Pin 3

Which pin are you calling pin 3? Lower-left? Lower-right?

9-DRVN is D501 0n Pin 3 and also D505
...
22-DRVP is D501 on Pin 3

Again, not possible. This would imply that DRVN and DRVP are connected together. Is there continuity between DRVN and DRVP, and if so, what is it?

19-DRV2 is Q505 on Pin 1
VGH is Q503 Pin 2
VGL is Q501 Pin 3
VGC is Q501 Pin 2 and Q504 Pin 2

What are you using as a reference for those pins, the picture of the diode I posted in page 2?

[rigeback]

Re: HannStar Monitor

As you said I tested the contenuity on the individual rails etc but to have more room I removed the power / video panel. Anyway I decieded to go through the power check afterwards starting at VDD+9 Volts and there was nothing, so I checked the incoming power at TP and there is the 5.3 Volts but when I check F1 I get nothing on both sides??
Some thing is real strange here because when I unpluged the board and checked the contenuity from F1 out going and on board I get a signal.
I've tried checking the all the connections and every thing looks okay, the 5 volts is arriving on board.
These are the results I got testing the rails;
3-DRV1 is Q502 on Pin 3
9-DRVN is D501 0n Pin 3 and also D505
19-DRV2 is Q505 on Pin 1
22-DRVP is D501 on Pin 3
VGH is Q503 Pin 2
VGL is Q501 Pin 3
VGC is Q501 Pin 2 and Q504 Pin 2