The model is at4220b and power supply board is a delta dps-291ap , it happened after we unplugged it from the mains and then replugged it in, there is no standby light and it won't turn on, the fuse is good in primary power supply and we have 240v coming in, no leaking or bulging caps and nothing looks shorted or dry soldered, no power on pson wire , no 5v 12v or 24v on wires from the power supply board, I had power supply board out and looked it over, when I fitted it back in , I turned it on, heard a crackle from power supply board area and it powered up , with standby led and also turned on, when I pulled the power it would not come back on, I can use a ddm and repair car computers but could use some help with this , thanks in advance
Acer 42" LCD tv no power or stdby light
Collapse
X
-
Re: Acer 42" LCD tv no power or stdby light
Any pictures of the board?Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
-
Re: Acer 42" LCD tv no power or stdby light
When you do a picture show where the resistor is/was.
Have you taken the resistor off the board - sometimes is blows off one side
but you can see the markings left on the other side?
If its burnt try cleaning with isopropyl alcohol.Please upload pictures using attachment function when ask for help on the repair
http://www.badcaps.net/forum/showthread.php?t=39740Comment
-
Re: Acer 42" LCD tv no power or stdby light
I replaced the resistor, it was 0.1ohms, was a carbon resistor but could only get a 5w wire wound resistor, the board had been out all night and when I went to put the resistor in had a few big sparks as cap discharged, about 4 sparks in total. all in and still nothing,
one photo is of the board and I have circled in red where the resistor sits underneath. the second photo is the replacement resistor (red circle) and the FET that it connects to (black circle) there is a cap that jumps the same gap as resistor,
Comment
-
Re: Acer 42" LCD tv no power or stdby light
Can you please use the attachment function to upload the pictures? Please do not post the pictures in line.
I would like to see the good pictures of the bottom side of the board, also in 1/4 section so I can trace the connections.
That resistor may be fusible resistor for circuit protection for the B+, cannot tell until I see the bottom side of the board.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
-
Re: Acer 42" LCD tv no power or stdby light
well I cant edit the last post anymore so will have to reply.
the mosfet is a n channel, number on it is 15n60c3, anyone know what it does? if it has shorted will this blow the fuse?
update: just unsoldered both FETS and both are shorted. will replace tomorrow.
Question. is there any point updating this thread? , just thought it might be useful for anyone else with problems of a similar nature. I hate it when people ask questions, get answers, then go away and not follow up with the solution or a reply, even "yes this fixed it" would be good enough.Last edited by slowcap; 04-09-2013, 03:17 AM.Comment
-
Re: Acer 42" LCD tv no power or stdby light
Question. is there any point updating this thread? , just thought it might be useful for anyone else with problems of a similar nature. I hate it when people ask questions, get answers, then go away and not follow up with the solution or a reply, even "yes this fixed it" would be good enough.
The last post by another member was Less than a full day ago! If it was a week--Then I could understand your irritation, but a few hours!
Give 'em a chance!TELEFIX
How PLASMA SCREENS WORK, X-SUS and Y-SUS what they do--
http://www.irf.com/technical-info/appnotes/an-1088.pdf
PLEASE DO NOT EMAIL ME PRIVATELY FOR REPAIR ADVICE. QUESTIONS BELONG ON THE FORUM!Comment
-
Re: Acer 42" LCD tv no power or stdby light
Well, I download the pictures, some are not in focus.
Do know how long it will take me to look at the traces on the board based on the pictures and tray to draw up the diagram without having the board in front of me?
If that is too long to wait, then I am sorry for asking for good clear pictures.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
-
Re: Acer 42" LCD tv no power or stdby light
Sick 'em!!!
Listen this is a good place for answers but you have to be patient. I have a few pieces needing repairs that have been on my bench for a week or so because I can't find manuals. It takes a while and these people aren't paying the bills by replying to this thread. Hell, I am at work to pay my bills. I am betting, because I haven't had time to actually go over the blurry pictures, that more than just a resistor is bad. That resistor is probably meant to blow because of another failure (0.1ohm is usually a fuse resistor). More information is needed, like a schematic, to find out what that resistor is protecting and what it is protecting that component from.Comment
-
Re: Acer 42" LCD tv no power or stdby light
This is what I get from looking at the poor quality pictures.
Q301, Q303, IC300 should be replaced. The component around the Gate drive circuits of Q301, Q302 also must be checked damage.
Q808?? (PFC Voltage booster) need to be checked also.
The 12V, 24V rectifiers in the 12v/24v section also need to be checked.
You should put a 75~100W lamp in series with your power cord so you will not keep blowing the new fuse if the shorts are not located, the lamp will light up brightly if short circuits still present.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
-
Re: Acer 42" LCD tv no power or stdby light
Thanks for the reply have ordered the new mosfets from uk, will look at the other components tomorrow,
The post about replying was not directed at people who generously give up their time to help others, it was more intended for other people who ask questions and get help but never return to give the results, IMHO a lot of new threads could be avoided if a final post said "yes that fixed it" , I'm not talking about this awesome forum but from my hours of searching other forums and google results that don't have a conclusion, leaving me asking well did it work or did the person just give up and buy a new unit or bin it, sorry if I didn't make myself clear, I would be happy if a few days passed before I had a reply.
on a side note, ive been looking into why all 3 legs of the fets had shorted, and from my results heat is the killer, but its no too common for all 3 to be shorted, usually just 2 legs short. could a failed driver cause the fet to short this way?, I understand that the driver would now be receiving the full current as it backtracks up the gate, from the board that will be ic300 for q301 and q302.Last edited by slowcap; 04-10-2013, 04:18 AM.Comment
-
Re: Acer 42" LCD tv no power or stdby light
If the one of the IC Gate drive out put stuck HIGH that MOSFET will be fully on, so when the other MOSFET in this half-bridge drive circuit turn on, it will be like putting dead short on the B+ LINE.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
-
Re: Acer 42" LCD tv no power or stdby light
That is exactly what seems to be happening, is there a way to test the gate drive circuit with the mosfets removed?, as I'm having to import them from uk to newzealand would rarer not blow up some new ones, I am looking to buy an oscilloscope in a couple of weeks, no help right now of course.Comment
-
Re: Acer 42" LCD tv no power or stdby light
That is exactly what seems to be happening, is there a way to test the gate drive circuit with the mosfets removed?, as I'm having to import them from uk to newzealand would rarer not blow up some new ones, I am looking to buy an oscilloscope in a couple of weeks, no help right now of course.
Be sure to check the bridge rectifier to see if it is shorted or not. Also check the fuse, if you haven't already.
Refer to post number 13, budm is right about replacing all the parts involved with the mosfets.Last edited by ben7; 04-10-2013, 12:52 PM.Muh-soggy-kneeComment
-
Re: Acer 42" LCD tv no power or stdby light
You better replace the IC rather than taking a chance of blowing up your new MOSFETs. I ave a feeling the Gate drive components (didoe, resistors) are likely to be damaged when about 400V is dumped (shorted Drain to Gate) through those sections.Last edited by budm; 04-10-2013, 02:01 PM.Never stop learning
Basic LCD TV and Monitor troubleshooting guides.
http://www.badcaps.net/forum/showthr...956#post305956
Voltage Regulator (LDO) testing:
http://www.badcaps.net/forum/showthr...999#post300999
Inverter testing using old CFL:
http://www.badcaps.net/forum/showthr...er+testing+cfl
Tear down pictures : Hit the ">" Show Albums and stories" on the left side
http://s807.photobucket.com/user/budm/library/
TV Factory reset codes listing:
http://www.badcaps.net/forum/showthread.php?t=24809Comment
-
Re: Acer 42" LCD tv no power or stdby light
Muh-soggy-kneeComment
-
Related Topics
Collapse
-
by sam_sam_samI have wanting to do this project for quite sometime now and I finally found a switching power supply that will work on this desoldering gun station ZD-915 that the original switching power supply took a shit and just was not worth trying to fix it because this switching power is not quite big enough to handle the heater element and the vacuum pump
One note when I tested the switching power supply and the voltage control board I noticed that this desoldering gun heat up much faster than the original switching power supply which I was really surprised by to the point that I might buy... -
Have had two Acer K272HUL monitors die with the same symptoms:
- Blue power light is illuminated while the monitor is plugged in
- Black screen (no splash screen, etc.)
- Power button doesn't do anything
Opened it up and checked for bad caps and components, evidence of burns, etc. - everything looks fine.
Power supply voltages are fine.
There are some signal lines on the power supply harness that goes from the power supply to the logic board, not sure what these should be at.
Anyone have any ideas?...-
Channel: Troubleshooting Computer Displays
12-09-2023, 10:22 PM -
-
by sam_sam_samI have been working on this concept for quite some time now with limited success but recently I found a switching power supply that is setup for the voltage that this soldering station needs to operate at however it also needs part of the secondary circuit from the original switching power because you need several voltage rails
I once tried to get a ZD-915 desoldering station to work on a 18 volt battery power supply but unfortunately things did not go well but I did find a work around but I might try this idea again but going at a little differently more about this another time... -
by JimBanvilleThe sub developed a constant popping every couple seconds from woofer and power LED flickering with nothing but wall AC connected. Connecting an audio cable didn't change anything. It doesn't play but a second or two of audio in between the pops.
Opened it up and discovered the power supply is making a faint clicking or ticking sound.
I measured the amp's output to the woofer and it pulses up to 50mv DC to be driver. The pulses coincide with the power supply ticking/clicking.
I measured the power supply output going to the amp board and it too has this pulsing. Voltage cycles...-
Channel: Troubleshooting Audio Equipment
-
-
by shovenoseHi all,
I have a cheap rainbow christmas light set off Amazon which has this little power supply that has a button to change modes. I had a white set with the same power supply that I returned but I can't find any other rainbow themed ones that don't use this setup.
Anyway, the problem is every time you unplug them and then plug them in it reverts back to "Combination" mode which cycles through all these annoying tacky effects instead of going back to what you had selected or at least defaulting to "Steady on" which is what I want. So I'm thinking I can just...1 Photo - Loading...
- No more items.
Comment