Hannspree HF257 w/bad backlight

[rasterdan]

I have a Hannspree HF257 25" display that goes black after a couple seconds. After reading many posts, I replaced all of the caps on the board even though the cans did not looked popped on top. I also replaced the 12 v voltage regulator for good measure since the 12 v would shut down after a couple seconds. One of my friends said that was because it was probably in over current and it is one of those non-breakable regulators with a safety built in.

So, all the caps and regulator replaced, still have the same problem. I can see with a flashlight that the display is working, just no backlight. I suppose that leaves the inverters. I have been looking for the inverters on many sites and while you can buy just about every one on earth, you can't buy this one.

After searching, it looks like this may be the same inverter on the TDK XAD819AR inverter but I can't seem to find that one either.

I got this monitor for free and the problem doesn't seem like it should be so difficult to fix. I also reheated several solder joints that looked like they could have had ring fractures, I even pulled the inverters and reinstalled in the opposite position to see if that made any difference and still no help.

I would also be interested in figuring out what is pulling down the 12v.

One last bit of information, before i replaced the caps, i replaced the 12V regulator and the monitor worked for a few minutes before shutting down. Is it possible that the caps have damaged the regulator and now that I have new caps, the regulator needs to be replaced again? I know some circuits once they have tripped a few times the safety portion is damaged and will just keep shutting down.

Thanks for any help on this one. It seems to have a very common failure mode with this model but I have not seen any posts that have actually fixed the monitor except one where they jerry-rigged another model's power supply into the monitor. I think that is a bit extreme.

[retiredcaps]

Re: Hannspree HF257 w/bad backlight

I have a Hannspree HF257 25" display that goes black after a couple seconds.

"2 seconds to black" can be

a) bad caps
b) bad inverter transformer
c) bad ccfl and/or wiring

Since you already replaced all the caps, see

http://lcdparts.net/TransformerDetai...ProductID=2796

for b).

All the above are explained in more detail in posts #13 and #14 at

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

[rasterdan]

Re: Hannspree HF257 w/bad backlight

Replacing the caps (even though they looked ok) solved the 12v problem. I still had the 2 second to black.
I pulled the inverter transformers and they measured both the same and very close to what the generic replacement said their values were so I am assuming they are ok. I can unplug the back light and the power supply still shuts down.

I believe it is a bad surface mounted Current Mode PWM controller. It seems to have the same voltage and wave form coming out of every pin except ground. The DVM also has every pin about the same whether power on or off, startup what ever. I may or may not continue with this piece o junk. Most of the blogs have wound up junking this board and you can't find one online. It now has some good parts for other repairs.

All the diodes and transistors etc seem to be ok, the 5 and 12v is working perfectly. I have wasted too much time on this beast.
I have a Samsung repair that should be an easy cap replacement (blown cans). That will solve my third monitor need for now. Before long, one of the neighbors will give me another dead one to dink around with. I have seen other power supplies used on this monitor so I may try a different supply when one comes along.
Thanks for the advice.

[sparkythefiredog]

Re: Hannspree HF257 w/bad backlight

I have one of these I found on the road dead. It had a burned CCFL wire and a burned CCFL connector, where the wire crossed the connector, bad assembly. I cut off the burned stuff and soldered on new wire and connectors with heat shrink insulation.
I found a jumper on the inverter labeled 7.5ma, 8ma. I moved the jumper to 8ma before I tested. I wondered if the jumper was there for CCFL aging compensation. I forgot about it.
I then tested, back light worked fine and stayed lit. I put the monitor back together.
Now, if I turn brightness below 65 or so, the back light goes out in a few seconds. The safety circuit shuts down the inverter if it detect over or under current. I assume the jumper sets the range of current for the safety circuit. But it may affect the PWM. Does your board have this jumper? My board has all TAICON caps, did yours?

[jetadm123]

Re: Hannspree HF257 w/bad backlight

I have one of these I found on the road dead. It had a burned CCFL wire and a burned CCFL connector, where the wire crossed the connector, bad assembly. I cut off the burned stuff and soldered on new wire and connectors with heat shrink insulation.
I found a jumper on the inverter labeled 7.5ma, 8ma. I moved the jumper to 8ma before I tested. I wondered if the jumper was there for CCFL aging compensation. I forgot about it.
I then tested, back light worked fine and stayed lit. I put the monitor back together.
Now, if I turn brightness below 65 or so, the back light goes out in a few seconds. The safety circuit shuts down the inverter if it detect over or under current. I assume the jumper sets the range of current for the safety circuit. But it may affect the PWM. Does your board have this jumper? My board has all TAICON caps, did yours?

The power supply on your monitor is probably used for several different models. The 8mA setting would be used on a larger screen as those CCFL's require more current. If you moved the the jumper back to 7.5mA can you increase the brightness without causing a shutdown?

[sparkythefiredog]

Re: Hannspree HF257 w/bad backlight

I have the hf257 back together and it works for now. If it flakes out I will take it apart again.

[v3ng3nz]

Re: Hannspree HF257 w/bad backlight

I have the exact same problem

Searched online for a couple of friggn days for a replacement. Manufacture was no help, first I emailed for a new inverter and they said I could order the part. I called and waited bout 30 minutes for sales rep, which said no, he then said I could send it in for repairs... Then I asked how much is a minimum charge I would have to pay. Told me to call back in a couple of days and they would have a quote ready...... for a minimum charge. I didnt call back. Last time I am buying from this company - buy buy HANSPREE...

I eventually did the hack you were referring to and would work fine for a second and shut down..same problem. flashlight to screen showed image just fine. going to solder the old inverter back in and change jumper to 8.0 ma and see if fixes... will post back to confirm and see if it fixes

BTW Thanks for giving so much info in post!

PS: If this fails, am going to make a led bar for this thing.

[MikeB]

Re: Hannspree HF257 w/bad backlight

I have a HF257 that is dead as well. The usual screen barely on for 2 seconds and then black. I have read all comments/suggestions which will be very helpful, but my question is a very basic one - how to remove the back cover. I removed the four screws, but the cover is still very securely attached. I obviously don't want to break the plastic case. Is there another hidden screw holding this together? It's clear that you all have gotten past this stage. Any help/phots would be much appreciated. Thanks.....

[killian6pk]

Re: Hannspree HF257 w/bad backlight

Just for information purposes HannsSpree , HannStar and other names are used by this company. They produce monitors for Staples the office supply company and probably several more I have not found out about. From research into this company on the internet they seem to either be going into bankruptcy or just coming out of bankruptcy. I would be very careful in buying their product. I have searched repeatedly for service manuals etc. for them without any luck. If anyone has schematics or service manuals the the 19" models I sure could use a copy.

[killian6pk]

Re: Hannspree HF257 w/bad backlight

You need to watch video on You Tube about how to take these apart. They are not hard but, you can mess up the case pretty bad while trying to take them apart without learning how. Check the repairing LCD Monitors videos and most show how to take them apart. Also as said by someone earlier take plenty of pictures as you go through each stage of taking the monitor apart.

[MikeB]

Re: Hannspree HF257 w/bad backlight

Thanks. It's apart.

[rasterdan]

Re: Hannspree HF257 w/bad backlight

After changing the caps, the board was still not functioning properly. Recently I was Christmas shopping online and searched eBay for the power supply number and finally got a hit.

You can purchase an almost identical board on eBay for $34 - free shipping. Search by your board part number and you will find one one digit different (the board is for a HH251). I looked at it and it looked exactly like mine. I ordered it and it looks exactly the same and ... it works perfectly.
FSP060-2P109
eBay store "monitor-09"

[megaman007]

Re: Hannspree HF257 w/bad backlight

After changing the caps, the board was still not functioning properly. Recently I was Christmas shopping online and searched eBay for the power supply number and finally got a hit.

You can purchase an almost identical board on eBay for $34 - free shipping. Search by your board part number and you will find one one digit different (the board is for a HH251). I looked at it and it looked exactly like mine. I ordered it and it looks exactly the same and ... it works perfectly.
FSP060-2P109
eBay store "monitor-09"

I did did this following your advice and unfortunately for me, it did not fix my backlight problem. So I guess my monitor itself is bad. I was sure the board was the issue because the original was blackened and with the backlight turned down all the way I could still see my display on.

I don't think something I paid 34USD is worth shipping back to China, so if anyone in the USA or Canada is looking for one, try contacting me and you can buy the one I just got my hands on. Hey, beats waiting for a package from China. Right?

[jayoung]

Re: Hannspree HF257 w/bad backlight

What are the symptoms of your monitor currently? When turned on, does the display show for a few seconds and then shut off? Does the power LED stay green / blue?

You may have an issue with the ccfl's (disconnected wires, broken ccfl's, dead ccfl's, etc.) If this is the case, there are places where you can buy replacement ccfl's and install them yourself.

[megaman007]

Re: Hannspree HF257 w/bad backlight

the power light stays on and the display shuts down almost immediately. If I screw with it long enough to turn the brightness & contrast down, the display don't shut down. But once it turn it back up, it shuts down again. And with a white background, I can tell there is still a picture on, just not lite up enough to actually see what is happening on screen.

This made me assume if was the inverters and order the replacement power board. But, well, it turns out that was not what was bad, since it did not fix my problem. I'm not sinking one more penny into it. I've got a 24" Dell LED display to fill the gap and considering how shady the tech support at HannSpree is, I'm probably better off just selling the part & parting with the damaged display too.

[jayoung]

Re: Hannspree HF257 w/bad backlight

Could very well be aging ccfl's. As they age, they draw more and more current until it gets to the point that it trips the sensing circuitry causing the 2 seconds to black issue. With the brightness turned down, the current draw might be lowered enough to avoid the 2 seconds to black. Do you by chance have access to any "spare" ccfl's?

I purchased some replacement ccfl's from www.CCFLwarehouse.com through e-Bay not too long ago for a 19" monitor that I fixed. I didn't have any issues with them.

Hopefully you won't send the monitor to the landfill and instead find someone or someplace to "recycle" it. Where are you located? Someone on the forum may be interested in it if you decide to part ways with it. There are many places that do electronics recycling and would gladly accept it.

[PlainBill]

Re: Hannspree HF257 w/bad backlight

I'll second jayoung's comments. I'd suggest listing it for sale on Craigslist (or whatever equivalent is available in your area). I'd say someone would be eager to buy it and put $40 of CCFLs into it.

PlainBill

[megaman007]

Re: Hannspree HF257 w/bad backlight

If that's the case, couldn't I switch the 7.5ma/8.0ma jumper to provide more current and see if that fixes the problem? Or will that likely send the whole damn thing up in smoke?

Pennsylvania BTW

[PlainBill]

Re: Hannspree HF257 w/bad backlight

If that's the case, couldn't I switch the 7.5ma/8.0ma jumper to provide more current and see if that fixes the problem? Or will that likely send the whole damn thing up in smoke?

Pennsylvania BTW

By all means move it to see if it makes a difference. But in the designs I have studied, the OCP (over current protection) setting is separate from the lamp current setting. Changing the current setting will not affect the OCP trip point.

PlainBill

[silverdelta]

Re: Hannspree HF257 w/bad backlight

megaman007 do you still have the board available? I would be interested in buying it from you.