BUSH LCD27TV022HD

[ThomasPSmith]

This is my first posting on this forum from a newbie so please be patient.......

My son has a BUSH LCD27TV0022HD. He was watching it when the screen suddenly went off as if in stand by.

Enquiries on the internet revealed that this problem is well known and is associated with a failure of the power supply unit inside the TV. I have examined the TV and the said PSU is number type 17PW15 - 8 and the mainboard is 17MB11 - 6.

The serial number of the TV is 5915039 600450.

I have purchased a replacement and the replacement is an upgrade serial number 17PW20 V2. I have fitted this and connected it up following the instructions as closely as possible. I cannot follow the instructions exactly because the main board on my TV is 17MB11 - 6 and the mainboards mentioned in the instructions are 17MB11 - 5, 17MB11 - 7 not 17MB11 - 6. They all have slightly different connection points.

After studying my new PSU and Mainboard, there is actually only one way to connect the additional wire in the kit whilst following the instructions. So I think that I have connected the new PSU up properly. The instructions are very clear in that the new PSU is a updated direct replacement of the original with the addition of a slight change in wiring.

As you may have already guessed I am not a TV engineer but am quite technically minded.

The possibilities are of course that I have not connected this up properly (but it does power up but just in the same way as it was when it was faulty. It is possible but unlikely that the new power supply is faulty as it is supplied by the owner of this website!! Of course there is always the possibility that there is another fault aswell

I hope I have made sense with this story

Anyone who can offer useful advice then please don't hesitate etc and thanks in advance

Having done all this I switched the TV on to have exactly the same problem in that the screen flicker for only half a second, the led at the base of the screen remains green and I have perfect sound.

thx for reading
Tom

[G.v.t.v]

Hi Thomas sounds like your back light is out! therefore meaning the invertor board is faulty and not the power supply. Hope this helps
                         Regards G.V.Tv

[ThomasPSmith]

G.v.Tv

Many, many thanks for this. I don't want to spend too much money on this set as it will very easily become cost effective to buy new.........However, having said that, if I can repair cheaplt etc I will carry on with my journey into the innards of this TV set. Please tell me in simple layman's terms how I get to this board and is it not possible (I assume a backlight is a light) just to replace the light. Is there a simple way to identify the failure? I have had a quick look around and seen a price of £120 to replace the inverter board so that is not an option.

I would just like to thank you again for your reply and info

Tom

[G.v.t.v]

 :mellow:
    Hi Tom
              Backlight is a row of flouresent tubes behind the screen, its most unlikely these are faulty. Identifying invertor board is fairly simple, as it has 6 or 7 leads connected over its whole length, comfirming that its faulty could be difficult without a scope, also there are very high dangerous voltages in this area.
              I may be as well to forget it and flog it off on E-Bay as spares or repair, to recover the cost of new power supply, which you can also sell.

                                            Regards G.V.T.v

[ThomasPSmith]

Thanks again...........I think I have made progress. I have identified and removed the backlight inverter board (I hope you are impressed!!......lol). I think they are called the SMD transformers (there are six) - the 7 black IC's in mounts. I have taken the opportunity to measure resistance between the solder points (after seeing a diagram in some obscure website) all have the same characteristics except one which has an open circuit between the 2 pins at one end of the chip )whereas the others all show about 950 ohms. The board is a Darfon V070 - 001. The number across the back of the SMD transformers is 4006A540.021 GP (the ? faulty one) the others all have similar but variable numbers after the dot. These chips look like they are removable but I am scared to use any force in case I damage it.
Is it possible that I may have found the fault or am I talking complete nonsense!?

Please reply
thx again
Tom

[mulja]

Sorry for late answer to busy

Please can post a pictures of inverter board to see what transformers looks

[terminator2k2]

i think you are measuring the secondary side of the transformers.??

if i remember rightly the primary side of the transformers should read roughly short circuit and the secondary side of the transformers usualy about 1000 ohms or 1kohm(same thing). now what i would do is desolder the faulty transformer....if you have no proper equipment then solder all points of both sides of the transformer then as you heat up one side gently lift that side up...not too much just so the solder isnt in contact with the pcb any more....then do the other side.  

replace the transformer and voila should be up and running....

[ThomasPSmith]

mulja - please don't apologise for a late reply, this forum is free and there is no obligation. Its reassuring that people are willing to share their knowledge.

terminator2k2 - thanks for your reply. I have done more research since my last post and now think I have nailed the problem (particularly after your last terminator. From research on the internet I have discovered that the  resistance across the transformer on the bottom pins is supposed to be 950 ohms (almost what you say, teminator.

I have managed to find a place that will supply the smd transformer and hopefully I can get away with a careful bit of soldering and have a successful repair.

I will certainly let forum readers know.

mulja/terminator hers is a pic of the offending item.

Thanks again for the replies.
Tom

[terminator2k2]

well if you have cross referenced the faulty one with the others and it reads open circuit then that should be it....also noticed the pins arent as close together on these transformers as ive seen..if in doubt in desoldering the faulty one , just cut the legs of holding the transformer to the board then just desolder what you leave on...will make the job a lot easier....also make sure the new one goes the right way round....thats if it can as it looks very symetrical.....

good luck with it bud....

[mulja]

See on the pictures check resistance beetwen
this pin must be 1kom if its is far lower or higher
transformer is faulty

find how many transformers is faulty

And check your pivate messages
for more info..............

[ThomasPSmith]

Mulja
thanks for this. Yes, one of the SMD transformers is definitely faulty. If you look at the board in the same position as your picture the one on the right hand side has an open circuit on the bottom two pins.

I will let you know whether I am successful with this repair.

Thanks
Tom

[ThomasPSmith]

  BINGO!!!!!!! Hooray................Success!!!!

Just managed to get the transformer fitted. I think the pcb was just not quite right at one of the pins as it picked up the copper track when I took it off (not me, 'guv I was dead careful!) after carefully scratching off the surface of the pcb I have managed to solder a piece of wire onto it which i could then solder onto the relevant pion of the transformer.

I think it looks like a gorilla has done the soldering but it is now working. I don't know how long for but I will just have to look out for a cheap inverter board for sale.

Many special thanks to everyone who advised mulja, Gv. tv, terminator2k2 and anyone who read the post.

Now I need someone to give me advice as to how to tune the TV......(I think it's always been used for games), so if anyone knows where I can d/l an idiots guide or give me a clue as to how I start the tuning process I would be very grateful

So thanks again for everyone's help

Tom

[ThomasPSmith]

    Further to my last post, I have now completely sorted this TV. Would you believe it, the aerial wire wasn't making it.

Thanks again, everyone

If anyone wants a power supply unit for this TV, It's a 17PW15 - 8 for a BUSH LCD27TV022HD. Please mail me!!