Hanns g 28" Monitor Power Supply Question

[PlainBill]

Re: Hanns g 28" Monitor Power Supply Question

Bill/Momanka,

I got the P/S board reworked and have very clean 5V, 12V, and 24V outputs at CN1 and CN3 under load (i.e. monitor turned on). The monitor turns on, I get a picture for 1 second, then the monitor turns off yet the blue led stays lit.

Where would you folks look to next?

Tentative diagnosis is two seconds to black. The inverter controller detects a fault condition and shuts down. To confirm, hook the monitor to a working computer and see if you can observe the desktop by shining a flashlight on the monitor screen. If you can, that confirms it.

#1 cause is bad caps, either in the 24V section of the power supply or the inverter. Test by replacing all caps in the 24V section of the power supply and the inverter with low ESR caps (if you haven't already done so).
#2 cause is one or more bad CCFLS, or the wiring to the CCFLS. Test by substituting a pair of good CCFLS for each pair in this monitor. (The test CCFLs do not have to be installed in the panel.)
#3 cause is one or more bad transformers. Test by measuring the secondary resistance of each transformer.

PlainBill

[retiredcaps]

Re: Hanns g 28" Monitor Power Supply Question

Everything that PlainBill describes is explained in more detail in posts #13 and #14 at

https://www.badcaps.net/forum/showthread.php?t=10419

[alexanna]

Re: Hanns g 28" Monitor Power Supply Question

Everything that PlainBill describes is explained in more detail in posts #13 and #14 at

https://www.badcaps.net/forum/showthread.php?t=10419

On step #5 Bad CCFLs.On this monitor, It would be a good idea as PlainBill suggested to substitute good CCFLs in pairs.[ equal length test CCFLs].Two from a 19" or two from a 22",not one from the 28" and a smaller CCFl

[Steven_C]

Re: Hanns g 28" Monitor Power Supply Question

It was a fault condition Bill. I had bent one of the 7 power inverter pins going to the lcd and hadn't caught it until this second time after reading your post and removing and reinstalling. The connector to the lcd wouldn't fully seat so I rebent the pin. All 7 CCFL's (a high voltage transformer for the lcd display I assume?) are connected. The fault condition is now gone.

It looks like the monitor is now fully functional again.

BTW, are the panasonic ecg caps one of the recommended caps? They are the option Digikey gives for aluminum electrolytic caps.

[Steven_C]

Re: Hanns g 28" Monitor Power Supply Question

So the "CCFL's" (high voltage transformer) can be substituted from smaller monitors? There are 7 of these transformer units on the board but it looks like there are 2 per install.

If using 2 in series from the 19" or 22" in series, I assume the step up for the two is equivalent to one of these ccfl's?

[retiredcaps]

Re: Hanns g 28" Monitor Power Supply Question

BTW, are the panasonic ecg caps one of the recommended caps?

A list of low ESR caps can be found at

https://www.badcaps.net/forum/showthread.php?t=2280

Certain applications like a SMPS require low ESR caps. Other areas of the monitor like caps on the logic board may not require low ESR caps.

[Steven_C]

Re: Hanns g 28" Monitor Power Supply Question

That answers my question regarding CCFL's and which electrolytics you folks recommend.

BTW, would forced air on the electrolytics increase their life? There appear to be electrolytics which quickly fail on this monitor. I purchased it as a refurb (and after opening it, it clearly had been repaired my the manufacturer previously) and it lasted 7 months for me. Bill indicated in another post that reducing the brightness to 30% increased their life so I've done this.

[PlainBill]

Re: Hanns g 28" Monitor Power Supply Question

It was a fault condition Bill. I had bent one of the 7 power inverter pins going to the lcd and hadn't caught it until this second time after reading your post and removing and reinstalling. The connector to the lcd wouldn't fully seat so I rebent the pin. All 7 CCFL's (a high voltage transformer for the lcd display I assume?) are connected. The fault condition is now gone.

That is one of the least likely causes. You are only the second person to admit having done that.

That answers my question regarding CCFL's and which electrolytics you folks recommend.

BTW, would forced air on the electrolytics increase their life? There appear to be electrolytics which quickly fail on this monitor. I purchased it as a refurb (and after opening it, it clearly had been repaired my the manufacturer previously) and it lasted 7 months for me. Bill indicated in another post that reducing the brightness to 30% increased their life so I've done this.

Force air will help, but unless the design is REALLY bad, the internal temperature isn't an issue. The cause in most cases is the manufacturer using REALLY crappy caps.

PlainBill

[momaka]

Re: Hanns g 28" Monitor Power Supply Question

Force air will help, but unless the design is REALLY bad, the internal temperature isn't an issue.

In this monitor, it might be. I was looking through the pictures in heli2reg's thread, and the video/logic board and PSU board on his monitor did have a few spots that were slightly darker from heat damage. There were caps in those areas too.

BTW, are the panasonic ecg caps one of the recommended caps?

If I remember correctly, EC series from Panasonic are general purpose caps (i.e. not low ESR).

So the "CCFL's" (high voltage transformer) can be substituted from smaller monitors?

CCFL - Cold Cathode Fluorescent Lighting (the thin lights inside of the LCD panel).

By the way, congrats on fixing the monitor!

[PlainBill]

Re: Hanns g 28" Monitor Power Supply Question

If I remember correctly, EC series from Panasonic are general purpose caps (i.e. not low ESR).

You don't; Steven_C asked about ECG, the Panasonic division that produces electrolytic caps. On Digikey the manufacture's name is Panasonic - ECG. There is no EC (or ECG) series electrolytic cap from Panasonic; there is an ED series which is a general purpose type, so you were close.

PlainBill

[Steven_C]

Re: Hanns g 28" Monitor Power Supply Question

When I selected the caps from the parts selector, Digikey gives the Panasonic ECG as a global selector. After looking at the caps selection post, I discovered that some of the caps I purchased were FM and some FC.

And now I understand why the global listing for Digikey for Panasonic is ECG.

These electrolytics are a new thing for me. I was an EE in the defense industry for a decade. Electrolytics are expressly prohibited by all customers so looking for them right off the bat (in addition to having no schematic) is a very new experience. Caps just aren't a common failure on most defense designs. The commercial folks are much more cost conscious than the government so the design parameters differ, particularly with these electrolytics. My buddy warned me about this 7 or 8 years ago about dealing with commercial electronics. He also warned me about isolation transformers and their necessity but I didn't understand what he was talking about at the time. The datasheet Bill posted helped me out.

[momaka]

Re: Hanns g 28" Monitor Power Supply Question

You don't; Steven_C asked about ECG, the Panasonic division that produces electrolytic caps. On Digikey the manufacture's name is Panasonic - ECG. There is no EC (or ECG) series electrolytic cap from Panasonic; there is an ED series which is a general purpose type, so you were close.

Thanks for the correction, Bill . Way back (a few years ago?), I did order from digikey once and I do remember seeing some E* series from Panasonic so I assumed ECG was for EC.

[jammtek]

Re: Hanns g 28" Monitor Power Supply Question

I have the same problems with the identical PSU But From an viewsonic VX2835WM. I am wondering If anyone has the numbers or value/type of D601,D603, and D604?
The IC's are marked:
PRIMARY(HOT) SIDE
U201:LM393N
U102:L6598D
U202:LMC555
U101:L6562D
SECONDARY(COLD) SIDE
U801:LM324D
U501:3037CS
U601: DM0265R

[momaka]

Re: Hanns g 28" Monitor Power Supply Question

I have the same problems with the identical PSU But From an viewsonic VX2835WM. I am wondering If anyone has the numbers or value/type of D601,D603, and D604?

Why, are they shorted?
I don't know the numbers, but I would guess they are 1.5A to 2A, fast recovery rectifiers, judging by their size.

[vmsremy]

Re: Hanns g 28" Monitor Power Supply Question

Hello
i also have the same power supply dead on the same hannsg monitor. it seems to have burned, some components are really dark : Q601, Q501, Q502....
do you have technical spec of this power supply? schematics?
could you please share them? thanks in advance. ( sorry for my bad english, i'm in france )
remy

[Falcon99]

Re: Hanns g 28" Monitor Power Supply Question

I also think this Power supply might have a temperature problem. When i opened up my 28" Hanns G, some parts of the power supply board seemed to be darker than others, so they must have become really hot. In my opinion momaka is right if he says that the board design is really bad.

My problem was that the display turned itself on after a while of standby (yellow LED). It then showed a blank blue screen (not the windows BSOD!) and the status LED was lighting blue. A complete recap seems to have fixed the problem, but i am still testing.

when I replaced C205 (which is an electrolytic next to U201), a tiny part of the corner pad that connects to R216 which is on that ground chain lifted/came off.

The same thing happened on my board, but i think this came by me being not careful enough when removing the C205, thus damaging the pad. But repairing this did not solve the problem i mentionened above.

[Dax Corrin]

Re: Hanns g 28" Monitor Power Supply Question

Where would one probe to test the 5VSB on this power supply to make sure it is working? I have 2 of these Hanns-G 28" monitors and both went belly-up. I was able to get one of them working again but now I have the "press the power button multiple times and sometimes it comes on" problem. Today it came on "blue light" for about a second and back off, then nothing. All the "big" caps have been replaced, but not the small sized ones.

[Dax Corrin]

Re: Hanns g 28" Monitor Power Supply Question

UPDATE: I found the 5VSB test point by looking at a picture on one of the other threads on these monitors, it was bouncing all over the place. We had replaced the 2 470-10V caps already, but I put in 2 470-25V caps, still no go, but the 5VSB was then stable. I noted the new caps had started to swell a bit already. The I looked at a picture that had the values of some of the smaller caps that didn't come in the repair kit, and I noted 3 22-35V caps that I happened to have lying around, so I replaced the 3 of them. The traces started to pull up on one of them, but after I was done I had good continuity froim the cap lead to the nearby SM resistor. So, I dropped it back in..and YES! Blue light! I turned it off and on 3-4 times, came right on. So, I buttoned it all back up and YES! the backlight comes on and the "No video input message came on just like it should. So, now I'm going to replace the 3 caps in the other power supply and see if I can bring that one back too.

[Dax Corrin]

Re: Hanns g 28" Monitor Power Supply Question

Update 2: After replacing the same 3 caps in the second power supply, I now have good solid blue light, but now the backlight shuts down after about 10 seconds. On to troubleshooting that issue, I'll start with the 24V circuit and move on to the inverter board after that.

[momaka]

Re: Hanns g 28" Monitor Power Supply Question

I noted the new caps had started to swell a bit already.

I hope you put those caps in the right way, otherwise they will eventually pop and die (usually within seconds) and you'll be left with a dead monitor again. Electrolytic caps have polarity and you have to match it to what's on the board. Electrolytic caps will in almost all cases have a stripe on one side - this is the negative (-) side. The other side goes to positive (+) on the board.

Also, where did you buy your caps?