Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

[tom66]

I am getting this TV tomorrow, if all goes well. I'll post the model # when I get it.

User reports that over the past few days the picture has gone with sound, followed eventually by the sound as well a couple days later. The green power LED remains lit.

To me, it sounds a lot like bad capacitors on the power supply for the inverter, which sometimes also powers the audio amplifier. This would explain the delay in sound failing, as the audio system uses less power, so may have worked with high-ESR capacitors.

If anyone has serviced one of these - any helpful hints/tips?

From what I can work out, Hanspree is just another budget TV brand, but they might make their own parts, including panels (HannStar display.) Made in China, probably...

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

Yay. Got it home. Found two bulged caps on PSU. CrapXon specials. 1000uF 25V -> measures 290uF 0.96 ohms. 220uF 35V -> measures just 28uF 3.2 ohms. Testing others for ESR too. Nice FSP power supply, too... shame about the caps!

[Th3_uN1Qu3]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

HannStar is the parent company, their products go by a few names: Hanns-G, Hannspree and maybe others i do not know. They manufacture displays and motherboards - the mobo in my DV9000 is made by HannStar.

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

Thanks for the clarification

I tested what I think is the 12V rail and it measured 4.2 - 4.6V, so I'd say it was pretty fubar'd.

However, I replaced the caps and the board and it's still not working.

So, I proceed to test all the voltage regulators on the main board. 5/6 test good. One tests obviously bad: 1.1V output, rated 3.3V. However, I checked the input voltage, and it's only 2.06V with power attempting to turn on, and 0V in standby. This is clearly too low to output 3.3V.

There looks to be a device controlling power to the regulator - a MOSFET I suspect. It's getting 5.11V on one group of 3 pins, 0.5V on one lone pin (probably gate) and 2.06V on the output. If it's a P-channel, 0.5V should be enough to turn it on (assuming source is the 5.06V), as that's -4.5V gate-source. However, I was under the impression most MOSFETs failed short circuit; a decrease in conductivity (or similar) sounds rather strange. I'll perhaps try bridging it tomorrow (it might just be a power-save feature), but I need some sleep now.

[retiredcaps]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

HannStar is the parent company, their products go by a few names: Hanns-G, Hannspree and maybe others i do not know.

There are many 28 inch Hanns-G monitor threads and the conclusion that I have come to is that they all run temperature hot which dries out even the good United Chemi-con KY caps.

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

There are many 28 inch Hanns-G monitor threads and the conclusion that I have come to is that they all run temperature hot which dries out even the good United Chemi-con KY caps.

This thing is full of Lelon and CapXon .

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

Okay, as promised... pictures.

Model is JT01 FT32. Strange model number! Sometimes known as XV32.

The MOSFET is this one: (but not an original Fairchild part.)

There's another one on the board. That one controls the 12V to the T-con and it appears to work fine.

The gate of the good pFET is 11.88V when off (same as source) and 0.02V when on. But the gate of the bad pFET is 5.0V when on, and 0.7V when off. A gate-source short (or leaky gate source) could explain the higher gate voltage.

Still, -4.3V should be enough to turn it on, unless it's not a genuine -4.5Vgs part (unlike in the Fairchild datasheet... could be counterfeit silicon.)

[MrWolf]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

First post guys !! Hi tom i found this guide on repairing the power supply on your tv. i found this very helpful when repairing the one i had. hope it helps you out .

Chris

[budm]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

Is this the power supply used in your TV? This power supply is used in VIEWSONIC TV also, and I fixed many of them with bad cap and shorted ZENER and transistor.

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

Thanks both. Yes, that's my PSU. I think my PSU is good though, all the output voltages are stable. I will check with a scope later for ripple. And I'll bridge that FET to see if I can get it to come on.

[Scenic]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

If you need a spare PSU, mainboard, inverter or T-CON.. PM me
I've got most of the innards of a Hannspree Xv32 somewhere. It was working but had a cracked panel "thanks" to an ebay seller who apparently didn't know an LCD is effin fragile.. >.<

I tried to get a defective one with a good panel for a while, but for some reason they go for nearly 100eur on ebay, which is a lot for a 32" 720p (1366x768) TV.. so that route didn't quite work out..

Attached a pic of the "repair kit" commonly sold for the PSU board used in these. Might wanna check the labelled components. They go bad when the PSU caps give up, which is a bit of a painus in the anus as most of them are SMD

edit: back when i got it (over a year ago), I looked stuff up on it. Apparently this "Hannspree Xv32" is 95% identical to the "Viewsonic N3250W". Only differences are the case, stand and obviously the firmware (Hannspree vs. Viewsonic logo)
http://www.geek.com/xyzimages/storie...50w-HDR-00.jpg

edit2: or was it the Viewsonic N3235W !?
http://www.hd.ca/viewsoniclcd/largeimages/n3235w.jpg

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

Okay, so PSU tests good. Low ripple on most rails, below noise floor on 5Vstby for my scope!

No backlight. So I'm thinking an inverter problem? And maybe the user accidentally changed sources or muted the input so the sound went away a couple of days later too.

Noticed the second FET was being strange too, but the gate was 0.02V. The source voltage was 11.88V, but drain was only 2.0V, similar to the other fet stuck at 2.0V. I'm not sure what to make of these readings!

But even with both shorted, it doesn't work.

I may have to take you up on that offer of a main board Scenic. I'm currently disassembling it to get to the inverter and will test that (fuses, transformers, drive waveforms.)

[shepp]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

there will probably be a cap that is used for the power on function, this could be dud, cant see on the pics of power board tho to point you in the right direction, had similar fault after replacing bad caps, but thanks to this site there was a little cap under a heat sink(not this model) that was stopping the power coming on, i replaced it and hay prestow it worked, i would think you would still get correct voltages for output but without the power on signal it wont work

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

there will probably be a cap that is used for the power on function, this could be dud, cant see on the pics of power board tho to point you in the right direction, had similar fault after replacing bad caps, but thanks to this site there was a little cap under a heat sink(not this model) that was stopping the power coming on, i replaced it and hay prestow it worked, i would think you would still get correct voltages for output but without the power on signal it wont work

I'm getting good PSU output voltages. The problem is main board or inverter, I think.

[shepp]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

did you manage to check the transformers etc on the inverter?

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

did you manage to check the transformers etc on the inverter?

I'm going to check them later tonight if I get the time. Means the back frame of the TV has to come off.

[tom66]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

Okay, so I finally got the back cover off (which is quite an operation...)

Disappointed to find a Chungwha LCD, as I consider those among the worst. (Poor motion performance, poor colour/contrast and worst of all, they develop mura after a couple of years.)

The inverter looked good on first sight, all fuses are okay. But the transformers on either end of the board tested at 90kohm - the ones in the middle tested around 9.4kohm. I'm thinking that it's quite likely I've got two faulty transformers... but I've never seen that happen before... and the symmetry of the failure (or not) is annoying my OCD brain!

Two inverter transformers are £20+ so I want to make sure it's definitely these at fault. Scenic, could you please test your transformers on your board and see if the measure 9.4k all the way through or if some measure 90k?

[shepp]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

might work out cheaper to find a replacement board, what is the number on the transformers, i have a invertor here that may have the same transformers

[shepp]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

the number on these is 4015A513010

[Scenic]

Re: Hanspree "Unknown Model" 32" LCD: No picture or sound, power LED

Not quite sure where I put the innards.. been a while.
I'll look for them, check the inverter transformers and report back.