HannStar Monitor

[momaka]

Re: HannStar Monitor

This morning I was reading the instructions for diode testing and its advised to use the same setting as contenuity on this tester?

Correct.
On most digital multimeters, continuity check is combined with a diode test.

D501 2-1=550 2-3=550
D502 2-1=550 2-3=550
D503 2-1=236 2-3=236
D504 2-1=235 2-3=234
D505 2-1=758 2-3=758
D506 2-3=231 2-3=1 ?
D507 2-3=165

No short circuits, so these are very likely good.
The "1" you got for D506 - that means the part you tested was either out of the multimeter's range on the diode test scale or the part is open circuited. This is normal. When removed from a circuit, diodes usually show a reading in one direction but open circuit in the other.

I take it that these "Q" parts are also diodes?

Not exactly. "Q" stands for transistor, but it doesn't tell you if it's a MOSFET or a BJT. BJT transistors are indeed 2 diodes sandwiched together, so you can get a diode reading if you measure them in the right way.
MOSFETs are a little different. One pin, the Gate, will always show open circuit when the MOSFET is measured out of circuit. The other 2 pins are Source and Drain. Sometimes you may and sometimes you may not get a diode reading between Source and Drain - it all depends on the type of MOSFET and the way it was designed.
---
Since nothing is getting hot as you said, the t-con may actually be working fine.
I'd say, check the small ceramic caps just to make sure everything is alright before assuming that. Just run a quick continuity check on caps C501, C502, C503, C510, C506, and C507. If none of them show short-circuit or less than 30 Ohms, then they're very likely good (and if that's so, then you don't need to post the measurements you get from them).

Also, from the new pictures you posed, I see the two test points I wanted you to check earlier - VGL and VGC (they are by connector CN2).
With the monitor unplugged, run a continuity check between each of these test points and ground and see if you get 30 Ohms or less.
Then check the voltage on these with the monitor plugged in and let me know what you get.

[rigeback]

Re: HannStar Monitor

Thanks for explaining transistors I got to admit that I have a lot to learn here.
Anyhow the C501 is the only one that gives a "1" both ways or its dead, C503 gives only .534 @ 2K.
VGL to ground resistance 99.6 (7.60 Volts) VGC to ground resistance 553 (5.60 Volts)
VGL + VGC resistance 563 (9.00 Volts) The resitance through VGC was hard to get so used the auto tester for the above results.

[rigeback]

Re: HannStar Monitor

Just want verify my tests as there might be a mistake!
Resistance @ 2K
VGL to groung = .0373
VGC to ground = 1 can't get a reading?
VGL + VGC = 0.572
VGL to ground @ 20V = 0.08 V
VGC to ground " " = 0.41 v
VGL + VGC " " = 0.33 v
With the small auto tester in the same sequence I got 095 MV, 410 MV and 440 MV which is considerably lower in mille volts! I'm not sure but my Sinometer might need new batteries!

[PlainBill]

Re: HannStar Monitor

Just want verify my tests as there might be a mistake!
Resistance @ 2K
VGL to groung = .0373
VGC to ground = 1 can't get a reading?
VGL + VGC = 0.572
VGL to ground @ 20V = 0.08 V
VGC to ground " " = 0.41 v
VGL + VGC " " = 0.33 v
With the small auto tester in the same sequence I got 095 MV, 410 MV and 440 MV which is considerably lower in mille volts! I'm not sure but my Sinometer might need new batteries!

I've been avoiding saying anything because I've been busy with other projects, but a constant problem has been an inconsistency in the information.

For example, 'VGL to groung = .0373'. What kind of DMM do you have? Most DMMs are 3 1/2 digit (the 1/2 digit is the leading digit, which can be either 0 or 1). A few are 3 3/4 digit DMMs - three full digits plus a leading digit which can be 0, 1, 2, or 3). .0373 implies you have a 4 1/2 or (4 3/4) digit DMM - not impossible, but very unusual. If you made a mistake and meant the reading is 0.373K (373 ohms), that may be reasonable. If that is correct, that says the resistance is 37.3 ohms - definitely a problem.

Next 'VGC to ground = 1 can't get a reading?' confused the heck out of me; I mistook the 1 for an I. We'll call that my problem.

The voltage readings also imply there is a serious overload on the VGL bus.

PlainBill

[rigeback]

Re: HannStar Monitor

Thanks for pointing that out Bill, I miss typed the numbers and it should be 0.373K (373 ohms), I try to use one meter for all the reading but when I get a "1" I try the other one.

[rigeback]

Re: HannStar Monitor

I think I'll try replacing C501 since the rest seems normal?

[PlainBill]

Re: HannStar Monitor

I think I'll try replacing C501 since the rest seems normal?

That is probably not the problem. I'm not sure of the current load on the supplies, but it is quite low given the value of the caps used. If I had to target a voltage rail to suspect, it would be VGL, and the resistance across C503 is the lowest.

PlainBill

[rigeback]

Re: HannStar Monitor

Well I changed out C503 and there seems to be a small change when testing VGL to ground I get 0.753 or 753 ohms although VCG to ground still gives a 1 and VGL + VGC give 774 ohms with tester on 2K for readings, I guess its still too low asthe screen is still white!

[momaka]

Re: HannStar Monitor

I just noticed there is one more test point, VGH (it's right next to VGL). More than likely, this is the secondary boosted positive voltage rail, not VGC.

That aside, we need to try a different approach here before you change any more components...
First, get the data sheet for the Max1997 IC (IC501) as you will be using it as a reference. For now, the only pages of interest are pages 13, which contains a sample circuit that is likely very similar to the one on your t-con, and page 30, which has the IC's pinouts.
Then, measure the voltages on the following pins of IC501 (with respect to ground):
Pin 4 (FB1)
Pin 10 (FBN)
Pin 18 (FB2)
Pin 21 (FBP)
These pins indicate which of the boosted voltage rails are working. Let me know what voltages you get.

[rigeback]

Re: HannStar Monitor

Thanks for your help and I should have waited before replacing any parts but got this new flux which I wanted to test and it works a treat after my little experiment.
I checked VGH to ground while I was at it and things don't look good 000 volts! The rest are as follows;
Pin 4 (FB1) 5.05V
Pin 10 (FBN) 000V
Pin 18 (FB2) 1170 MV
Pin 21 (FBP) 000V

[momaka]

Re: HannStar Monitor

Thanks for your help and I should have waited before replacing any parts but got this new flux which I wanted to test and it works a treat after my little experiment.

Yes, flux makes SMT work a breeze.

Pin 4 (FB1) 5.05V
Pin 10 (FBN) 000V
Pin 18 (FB2) 1170 MV
Pin 21 (FBP) 000V

Wow. Are you sure those are the voltages you got? If so, we have a problem.
FB1, FB2, and FBP should be close to 1.25V. FBN should be close to 125mV.
Try measuring those voltages again and see if VDD+9V is still 9v. Let me know if it's not
----
I also dug in a little deeper into the Max1997 data sheet, and found some more useful info - mainly, there's 2 other voltage rails besides VGH and VGL. One of them is very important and gives power to the main controller on the t-con, IC1. The voltages you got above for FB1, FB2, FBN, and FBP indicate that one (or more) of these rails has a problem and is likely pulling all of the other rails down with it.

So first thing you need to do is determine which rail is where on your t-con board so we can check and troubleshoot each one.

To do that, first locate pin 3 (DRV1) on the MAX1997 IC. Now, with your multimeter set to continuity check, you should find that one of the pins on one of the transistors is connected to pin 3 (DRV1). You'll know this when the multimeter beeps and shows a very low number (less than 2 on the screen).
Note that there are 5 transistors on your t-con: Q502 (the big one with 4 pins), Q501 (all the way to the left side, next to C523 and C524), Q504 (midway between Q502 and Q501), Q503 (below the MAX1997 IC), and Q505 (next to lower-left corner of inductor "4R7"). I'm using this picture as a reference:
https://www.badcaps.net/forum/attach...4&d=1318106711

Once you find which pin of which transistor is connected to pin 3 (DRV1), post the information here. Then repeat the same procedure above for pin 9 (DRVN), pin 19 (DRV2), and pin 22 (DRVP) of the MAX1997 IC - i.e. find the transistors to which these pins are connected to.

Next, do a similar procedure as above for VGH, VGL, and VGC - that is, connect one probe of your multimeter to VGH/VGL/VGC, and find which transistor it connects to.

All of this will give us a complete description of where each rail is located on the t-con. Once we know this, then we can test each rail's components thoroughly to see where the fault is.

This shouldn't be that much work - of course, if you think it is, then let me know. I hope I'm not giving you a headache with this stuff .

[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

[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

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.

[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.

[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

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!

[rigeback]

Re: HannStar Monitor

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

[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

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.