HannStar Monitor

[rigeback]

Re: HannStar Monitor

Thanks Bill,
I take it these transistors need to be changed out for a higher voltage like 20-25 volts to energize the video board correctly?

[PlainBill]

Re: HannStar Monitor

Thanks Bill,
I take it these transistors need to be changed out for a higher voltage like 20-25 volts to energize the video board correctly?

No.

There are a number of considerations involved in choosing a transistor for a particular application. These parameters include voltage, current, gain, frequency, power dissipation. When choosing a replacement, it's best to go with the same part number. If you must substitute, try to match the original voltage.

My point was that the specifications of the part - especially the maximum allowed voltage - will be much greater than the actual conditions. In your specific example - Gate source should -+25 Volts and the drain source 60 Volts - This means that the transistor should never be used in a design where the gate - source voltage is greater than 25 volts, nor where the drain - source voltage is greater than 60 volts. The specs say (almost) NOTHING about the voltage you expect to see in the actual circuit.

PlainBill

[rigeback]

Re: HannStar Monitor

Bill, This tells me a lot but whats the best course of action to get this monitor running?

[PlainBill]

Re: HannStar Monitor

Bill, This tells me a lot but whats the best course of action to get this monitor running?

It may not be possible. A white screen indicates a problem with the signal card, the cable from the signal card to the panel, or the panel itself. That's the first piece of bad news.

The second is that your methodology is wrong. You've been concentrating on the power supply / inverter; that is probably NOT the problem. You have a responsive signal card - granted, all that works is the power button, but that means a major part of the signal card is working.

The third is that while you have provided good pictures, you haven't provided a picture showing the dark lines. Specifically, are they a line of frozen pixels, or are they a smudge on the screen? Both are bad, frozen pixels are probably unrepairable.

The good news is that you HAVE provided pictures of the panel card. Perhaps I have missed it; have you checked F1? Have you checked for 5V on F1 while you have a white screen? Have you checked voltages around IC501? IC501 generates the voltages required by the LCD panel.

PlainBill

[rigeback]

Re: HannStar Monitor

Bill, I got the video board hooked up to the T-con board but the is no power entering the T-con, the CCFL lamps are disconected. Power is entering the video board 12, 5 & 3 Volts. I found the ICI-501 with no problem but I just don't see F-1, this was the first thing I looked for but can't find it!

[rigeback]

Re: HannStar Monitor

OK, To be certain about getting power to ICI-501 I hooked up the CCFL lamps and the T-Con board gets the 5 volts @ the ICI-501 for short burst until the video card goes into standby. So this seems to romove the power source and video card from the problem??

[PlainBill]

Re: HannStar Monitor

OK, To be certain about getting power to ICI-501 I hooked up the CCFL lamps and the T-Con board gets the 5 volts @ the ICI-501 for short burst until the video card goes into standby. So this seems to romove the power source and video card from the problem??

Correct. A quick summary of how these work: The power supply takes line voltage and converts it to 5V (for the signal card) and 12V (for the inverter). The signal card checks it's last known state. If it was On, or in Standby, it turns on the LCD panel and the inverter, then starts looking for video signal. If it doesn't see a video signal within a few seconds, it puts up a 'No Signal' message, then turns off the LCD panel and the inverter.

Take a look at the second picture you posted; it shows the panel card (or more correctly, the tcon). Look at the connector from the signal card. The left pin goes to R57. The next three pins are all tied together, and to one end of F1.

PlainBill

[rigeback]

Re: HannStar Monitor

Well thats a real small bugger and I'm glad I don't have to change it and yes it has contenuity.

[PlainBill]

Re: HannStar Monitor

Well thats a real small bugger and I'm glad I don't have to change it and yes it has contenuity.

IC501 and associated components generate the voltages required for the LCD panel. I'd suggest looking up the datasheet for the IC and checking if it is generating voltages. A common failure is the not-so-small SMD caps short out. Also, near the left edge of the same picture is a point labeled VDD+9V. I'd look for more and check the voltage is present. For the sake of convenience, you might want to hook a computer to the signal card so you can make sure the power will always stay on.

PlainBill

[alexanna]

Re: HannStar Monitor

IC501 and associated components generate the voltages required for the LCD panel. I'd suggest looking up the datasheet for the IC and checking if it is generating voltages. A common failure is the not-so-small SMD caps short out. Also, near the left edge of the same picture is a point labeled VDD+9V. I'd look for more and check the voltage is present. For the sake of convenience, you might want to hook a computer to the signal card so you can make sure the power will always stay on.

PlainBill

PlainBill I wish I had your eyes; I can barely make out F1 on the panel
Where do you see the IC501?

[PlainBill]

Re: HannStar Monitor

PlainBill I wish I had your eyes; I can barely make out F1 on the panel
Where do you see the IC501?

The identifier is on the lower right corner of the IC. If that doesn't help you, you should have no problem identifying IC302, it's the rectangular AD chip. Move in the 2 O'Clock direction (toward Q502).

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!

[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

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.

[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

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)

[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.

[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

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?

[rigeback]

Re: HannStar Monitor

Some clearer photos