vx37l no picture no sound

[tibimakai]

Re: vx37l no picture no sound

what you have to lose by trying to replace that U7?
Cut the legs off of that U7 and unsolder the tab, then remove each leg from the board.
Clean the pads with a wick and resolder the new regulator. If it won't work, then get another board, but if it will work, you will feel much better about yourself.

[retiredcaps]

Re: vx37l no picture no sound

Alternative removal method.

https://www.badcaps.net/forum/showpo...&postcount=139

[tibimakai]

Re: vx37l no picture no sound

That's just for him to make it easier with common tools. I have heat gun.
one like this:
http://www.amazon.com/Smart-Rework-S...5&sr=8-1-fkmr1

[eagle00799]

Re: vx37l no picture no sound

Cashkennedy I think this repairman was taking the easy way out by saying to replace the board because it would also be cheaper for the consumer (me) to have him try to hunt down the real problem on the board. That looks like a nice setup Tibimakai, have you ever tryed to reflow a Bga? The 67 series Samsung Dlp tvs have an issue with the Dnie chip that the lead free solder cracks over time creating poor contacts. JDelectronics will reflow that chip for $40. Bucks plus shipping cost. I got one of these for free because of this problem and the repairman told them they need to replace the board. Anyway I think I will get some wick and solder and give it a shot. I'm going to be busy the next coupe of days but I will try to get somedone with it as time allows.

[eagle00799]

Re: vx37l no picture no sound

I should proofread before posting, what I meant to say to Cashkennedy was it is often cheaper to replace the board than to have someone else try to find what specific part on the board is failing.

[eagle00799]

Re: vx37l no picture no sound

Here is a pic of the U7 that i will replace and now i will need to replace another transistor?? here is a pic of the part and the location on the board is right below where the T-conn board plugs in, the 2 circles by the capacitor,can someone help me out? what is this called and maybe a part number?

[budm]

Re: vx37l no picture no sound

That part in the picture #3 is just a wire with two ferrite beads on it to form a small inductor for filtering high frequency, you can use a new wire if the old wire is broken.
The U7 is a 1117 series adjustable regulator, you can see the two resistors on pin one which determine the output voltage. One resistor should be connected to pin 1 and ground, another one will be connected between pin 1 and Pin2 (output pin). You can calculate what the output voltage should be if you know the value of the two resistor.

[eagle00799]

Re: vx37l no picture no sound

Well guys I tryed removing u7 and accidently took out a real tiny thing in the CB37 spot right next to it. I have to say a 30 watt solder iron is not sufficient for the job. I would guess a 60 watt would be recommended? Any way of repairing cb37? I cant imagine soldering something that tiny so do I chalk this up as a lose?

[budm]

Re: vx37l no picture no sound

CB37 is just a small value ceramic cap which is in parallel with large elecrolytic cap to by pass high frequency noise, you do not need it for now. You can install ceramic disc through cap in place later on.
By the way, good soldering iron with 40 watts minimum should be used with proper size tip for what you are doing.

[selldoor]

Re: vx37l no picture no sound

You should remove the bigger cap next to the U7 - will give you more room and also less component to draw heat. Try pre heating the area with a hair dryer, you can also use two small irons if you have them

[tibimakai]

Re: vx37l no picture no sound

just cut the legs and unsolder the tab

[cashkennedy]

Re: vx37l no picture no sound

Im by no means a professional solder'er but this was one of the harder boards to fix because the part is surounded on 3 sides by tall caps.

If you have a replacement for the one next to the pins of the regulator , its not a bad idea to replace that cap while your at it with a low esr cap, that way you can take it out, replace the regulator while you have some room, then solder the new cap in,

These transistors are super fragile so while removing them the legs broke off on me regardless. Except for the middle leg which is attached to the large tab on the other side. But your welcome to clip the legs off like tibi recomends, deffinetly makes it easier, and also makes you need less heat, so since your soldering iron is on the low end, you might want to clip the legs as short as possible.

[eagle00799]

Re: vx37l no picture no sound

Ok can you guys give me some part numbers/brands for the wire with 2 ferrite beads,the regulator to replace the amc1117,and the ceramic disk to put in the cb37 location?

[selldoor]

Re: vx37l no picture no sound

Hi -I think at this point you only need to worry about the
1117 AMC1117 or FAN1117 If you can wait ,there are these ones on ebay.
Otherwise you may be able to get some on ebay in the USA. I dont think you will find a mainstream supplier - Try a want to buy in badcaps classified forum.

If you have still got the ferrite beads any bit of thin wire will do - one strand out of a thick wire etc.

As regards the capacitor do you still have it - it will be no easier to solder in a new one.
You will need to measure its physical size unless you know its uf value. You then need to find one that size perhaps in some junk electricals. You may be able to find some on ebay 100 for a dollar or so but budm said wasnt critical?

[eagle00799]

Re: vx37l no picture no sound

I was reading a post by ktulu909 and his problem was fixed by replacing U7 and budm posted links to mouser for the regulator but the link doesn't work on my phone. Ktulu909 had the same regulator,amc1117 0734. Can someone tell me the exact one he ordered?

[budm]

Re: vx37l no picture no sound

Most bypass cap (CERAMIC) for the electrolytic cap will typical be 0.1uf 25 or 50v rating.
You can get 1117 series regulator from Digikey or Mouser.
For example:
http://www.digikey.com/product-detai...ICT-ND/1301524

http://www.digikey.com/product-detai...PBCT-ND/483060

[eagle00799]

Re: vx37l no picture no sound

I see quite the price difference but I'm going to go with the cheaper of the two.

[budm]

Re: vx37l no picture no sound

U7 is an adjustable voltage regulator as shown in your picture, it has two network resistors at pin 1 for setting the output voltage. That is why I ask for the resistance of the two resistors to calculate the output voltage as designed.
You can see how to calculate the output voltage as shown in the spec sheet attached.

[eagle00799]

Re: vx37l no picture no sound

I finally got this tv back together. I replaced the U7 on the main board and it now works perfect. Thanks everyone for your help.

[budm]

Re: vx37l no picture no sound

Thank you for the feedback on your repair, the shop would have charge you a couple $100 for fix with $1 worth of part. Did you change that ceramic cap?
Job well done!