Hannspree HF257 2-3 seconds black

[jetadm123]

Re: Hannspree HF257 2-3 seconds black

Is C314 slightly bulged,or just the photo makes it look like it is ???

Doesn't matter, since he using a stock photo from shopjimmy.

[Rtech]

Re: Hannspree HF257 2-3 seconds black

Is C314 slightly bulged,or just the photo makes it look like it is ???

[Hippie459MN]

Re: Hannspree HF257 2-3 seconds black

S1>S2 = 997 consistent
S3>S4 = between 1004 and 1007

S3>S4 will not fluctuate while being tested but if I test once, wait a min or so, test again it will give a different reading. To me even the 997 sounds kind of high but I could be wrong for those inverter transformers as I do not have any kind of data sheet or any kind of info on them.

[selldoor]

Re: Hannspree HF257 2-3 seconds black

You need all 4 bulbs connected otherwise it flags it up as a fault and goes into protection.

Read this guide by retiredcaps - start at post 20 - also part at the end I think about test bulbs.by Budm post 25?

[selldoor]

Re: Hannspree HF257 2-3 seconds black

Test the Inverter transformers by checking the secondary wiring resistance.
POWER OFF, meter on ohms 2000 test S1>S2 and S3>S4 and post the results.

You might also want to resolder these connections.

[Hippie459MN]

Re: Hannspree HF257 2-3 seconds black

I put the original board back in today to try something and I was able to keep the screen lit up with the brightness down to 20 but as soon as I removed any number of the CCFL connectors from the board, 2 seconds and black. even with the brightness down to about 10. I didnt go any lower then that. I plug all 4 plugs back in and it stays lit up again so long as I dont bring the brightness up to much. So where to go from there? Could this rule out a CCFL tube? I am not going to let this monitor get the best of me just yet.

[Hippie459MN]

I have a Hannspree HF257 (25") and about a month ago had the bottom left side of the screen start doing a weird flickering and turning the monitor off and on seemed to fix it only to to it again the next day an turning it off and back on fixed it again. A few days later after not having any issues at all the screen just went black all together and turning it off then back on it would light up for about 2-5 seconds then black again so I brought it to a friends that said he would test some items and said he had an ESR tester for the caps. Later that day he said that I had some bad caps and a bad mosfet and had found a complete replacement board on ebay so I ordered it and when I put it in, it worked worse then the one I took out. The replacement one now would come on for 2 seconds and go out and this one has a very faint click and then an audible hum as soon as the CCFL tubes go out but turning off and back on it is quiet until the back light goes out again then the humming again. Turning the brightness down saw no changes.

So at this point I decided to put the original board back in and try turning the brightness down on the monitor and was able to get it to stay on as long as the brightness was below 23. About 25 it would go out again, 24 it would stay on for a good time and then go out, 23 it was on for a few hours before I turned it off.

Well, Now I have told this friend I am just going to replace all the caps and go from there and now he is saying they all tested good (None of them are puffed up or broke open that I can see) so I am not 100% sure now so going to do that in the next day or so.

Now I have been trying to find a replacement inverter transformer in hopes that that might be the issue but have had zero luck finding anything with the same part number and then in this post (https://www.badcaps.net/forum/showpo...24&postcount=1) I do notice them saying that the TDK XAD819AR has the same inverter and have found someone online with a few of them but I can not confirm that yet. I am waiting for them to get back to me. But I was wondering, what would be the best way to test this inverter and would anyone know of replacement that would work?

Also, I was leaning towards a CCFL tube being the culprit possibly but not sure of a really good way to test as I dont have another monitor or spare tubes to use to test with. Also, How much of a job is it to replace a tube if that is the case? I have never personally done one and my friend is saying its not worth it and way to big of a job but to me from what I have been looking at on youtube and stuff it doesnt really seem like it would be to tough. Anything to really watch out for when changing them?

Thanks for any help and here are some pictures. The first one is the inverter transformer with the part number, the next 2 are some pictures of the identical board that I had that are nice and clear. and the last picture is my actual board. Mine is missing the white silicone on the back side like the other photo. Looks to never have been on there at all. It is the best picture I could get with the camera I have.