HannStar Monitor

[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

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

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

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!

[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

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

[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.

[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

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!

[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.

[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

Some clearer photos

[rigeback]

Re: HannStar Monitor

Sorry about about the poor imformation, I forgot mention that the first resistance measurements were done at 200K on this meter in the picture. The measurements to the right were done with the power on for voltage. Yes Q502 read 4.87 volts 2-1, 2-3 2-4=0 (4 between 1 & 3)

This morning I was reading the instructions for diode testing and its advised to use the same setting as contenuity on this tester? I am a bit confused so added that picture for your comments.

Anyway I have retested all the diodes using this setting which infact seems to give a more efficient reading. I take it that these "Q" parts are also diodes?

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

Q501 2-1=648 2-3=638
Q502 2-1=601 2-3=598 2-4=0
Q503 2-1=734 2-3=1 ?
Q504 2-1=712 2-3=1 ?
Q505 2-1=519 2-3=1 this one might be shorting as the alarm sounds as in contenuity as I start to probe it, however when I use my auto resistance tester I get 2-1=1180
2-3=8.89 A bit confusing?

[momaka]

Re: HannStar Monitor

C501 = 0
C502 = 79.8
C503 = 65.9
C510 = 76.8
C505 = 0
C506 = 1 Fluctuating reading
C507 = 1 Fluctuating reading

D501 = 0 no reading (0.01 V ?)
D502 = 63.2 (0 V
D503 = 62.8 (0.19 V both legs)
D504 = 59.7 one side (0.19V)
D505 = 0 no reading (4.85V both legs)
D506 = 0.92 (0.03V on one leg)
D507 = 15.0 (0.17V)

To check these parts for short-circuit, you need to measure their resistance and not the voltage. You do this with the monitor UNPLUGGED.
When measuring resistance, also make sure to note the scale on your multimeter's display (i.e. is it Ohms, KOhms, MOhms, etc.).

Q502 has a total of 4 pins - do they all show 4.87 with respect to ground?

Just been doing some cold rechecks of D501 with my auto tester and I get 198.5 / 10.05

I'm guessing the first number is in Ohms and the second in KOhms, is that correct? Again, please put the units (and proper multiplier) for those numbers, otherwise they are pretty much useless.

[rigeback]

Re: HannStar Monitor

woops, Just been doing some cold rechecks of D501 with my auto tester and I get 198.5 / 10.05
C510 = 815. C501 give a qick reading and dies.

[rigeback]

Re: HannStar Monitor

Hi Mr Momaka, yes good trouble shooting but I'm not sure this ones going to make, I did some cold testing today on the parts you advised and then hot testing on the D & Q's.
I did not notice any parts getting warm or hot, really need a temprature tester.

C501 = 0
C502 = 79.8
C503 = 65.9
C510 = 76.8
C505 = 0
C506 = 1 Fluctuating reading
C507 = 1 Fluctuating reading

D501 = 0 no reading (0.01 V ?)
D502 = 63.2 (0 V
D503 = 62.8 (0.19 V both legs)
D504 = 59.7 one side (0.19V)
D505 = 0 no reading (4.85V both legs)
D506 = 0.92 (0.03V on one leg)
D507 = 15.0 (0.17V)

Q501 = 10/10 (0.32 Volts one leg)
Q502 = 67.2 /67.5 (4.87 V botth legs)
Q503 = 0 no reading (3.80 V one leg)
Q505 = 9.5 one side (0.04 v)
Q504 = 0 no reading ( 0.04 V)

[momaka]

Re: HannStar Monitor

After reading this thread I think I also have a cracked screen, I guess I'll keep the rest for parts for the next dump pick!!

Excellent troubleshooting so far!
Besides the 5v and the boosted 9v VDD+9v rails, there should be two other boosted rails derived from VDD+9v. And yes, those rails can cause a white-screen as well if one is missing or not up to spec.

I can't seem to find the test points for those rails (they are usually called VGH and VGL), but I'm almost certain those SOT-23 diodes under the inductor are part of that circuit.
Therefore, check the following parts for short-circuit:
C501, C502, C503, C510, C506, and C507. Those are located right under the inductor with the "4R7" on top of it. If they are not shorted, check diodes D502, D501, D503, D504, and D506. The arrangement of the diodes in D502, D501 and the others usually looks like this internally
https://www.badcaps.net/forum/attach...1&d=1294381123
(the anode may be switched with the cathode, though. I'm not sure, so check yours both ways).
There should also be another voltage rail going to IC1 - it's usually 1.8v or 3.3v derived from a linear voltage regulator. I don't see a linear regulator, though. Perhaps Q502 does this? It probably wouldn't hurt to check the voltage on it.

If you can't find anything wrong, just run the monitor for a few seconds and see if anything on the t-con gets hot. If one of those secondary boosted voltage rails is bad, IC501 and the surrounding components will most likely become hot.

[rigeback]

Re: HannStar Monitor

Well I done a fair bit of research today and even found a service manual, went through the t-con board checking all locations and then went back for another search and came across this message on BADCAPS Hanns-G HU171D & 171A - Blank (white) screen... both of them.
After reading this thread I think I also have a cracked screen, I guess I'll keep the rest for parts for the next dump pick!!
I've added a picture of the screen that indicates the marks.

[PlainBill]

Re: HannStar Monitor

Bill, you must have good eyes or good screen because these pictures are not so good, I'm going retake them in the sun light.
IC501 has the markings Maxim 199/E TJ606 +NDBM, I've searched but not found its data sheet, TJ apparently stands for temprature?
On VDD+9V I got 9,5 volts but I have not found and more points with the same details. Must be my eyes!

IC501 is probably a MAX1997ETJ. The main thing you should be looking for is a missing output voltage.

PlainBill

[rigeback]

Re: HannStar Monitor

Bill, you must have good eyes or good screen because these pictures are not so good, I'm going retake them in the sun light.
IC501 has the markings Maxim 199/E TJ606 +NDBM, I've searched but not found its data sheet, TJ apparently stands for temprature?
On VDD+9V I got 9,5 volts but I have not found and more points with the same details. Must be my eyes!