Pc Engine LT/Screen Repair

[BlueBMW]

Looking at those pictures I want to say first clean all that old solder off and wash off all that flux and crud.  Once you have a clean board you should be able to see where the traces were.  The first picture Ill bet just goes to that large green plane that is attached to the exposed copper your arrow points to..  The second picture is too dirty to tell anything useful from.

[wolfman]

Looking at those pictures I want to say first clean all that old solder off and wash off all that flux and crud. 

Well the solder that is left in the 1st picture I wanted to leave there since it still seems to have a solid and good contact to the board. I already cleaned everything and even scratched a little on the right contact to see if there would be any copper left (the brownish-blackisch rectangular spot left of the arrowhead), but there was nothing.

Is there a special cleaning fluid you recommend? I was using IPA so far, and q-tips.

[wolfman]

The second picture is too dirty to tell anything useful from.

Same here. That´s the best I could get with my camera. I thought someone here would know probably from experience or by memory where the trace would end or point to, so that I could solder directly to that point or part.

[BlueBMW]

Id have to take apart an LT to look and see.  Ill try and do that tonight.

[wolfman]

Id have to take apart an LT to look and see.  Ill try and do that tonight.

Awsome! Thanks a lot!

[wolfman]

Id have to take apart an LT to look and see.  Ill try and do that tonight.

Did you have a chance to find out yet?

[BlueBMW]

Did you have a chance to find out yet?

Alright... regarding CC505... the trace you pointed out does connect to that pad.  It also seems to have continuity to all three pins on the left side of that T500 component.  You should be able to solder to that trace that you pointed to in your picture.

Regarding CC506, the pad you pointed out does connect to that plane next to it.

[wolfman]

Thats great news, many thanks!   

Do you know what that T500 labeled "800V" is? Transistor? Or a MOSFET? What kind of?

I am not sure but in case I would have to replace it, it would be good to know....

Great Forum btw, its really cool how much help there is and so much USEFUL info.

[Fidde_se]

It's a coil, might be 800mH, very unlikely to go bad.

(Mosfet is a type of transistor)

[wolfman]

It's a coil, might be 800mH, very unlikely to go bad.

(Mosfet is a type of transistor)

A coil with 7 pins?

[Fidde_se]

Yupp, usually not all legs are connected, the same package can be used for the ones that use the extras legs, the ones that are not connected are then used for stability and support, and the ones that use more then one lining are transformers and they use them, if the big top would break off it would still work, it's just unmagnetic ferrite.

The only way for it to stop working is if one of linings burn off or the varnish on the linings gets so hot it melts and burn.

[wolfman]

So it is really cool and safe to solder the cap to it? Was a little confused as it looked like the copper trace went "back" to this piece...got the impression that I might fry something by accidentially shorting somewhere...

[Fidde_se]

Yes it is completely safe to solder back a capacitor there, the pads doesn't even seem to be damaged.

[wolfman]

So I played around with it the whole day, and I didn´t get the screen to work. Although everything is in place so far and I although I soldered new caps into it where I had access to (left out the tiny ones in the middle and on the front of the board) the screen never went on.

I opened up the top lid and disassembled the screen block to have a look at it. Guess what? Someone had tinkered around with it and damaged a ffc. I left it the way it was and modded a 3.5" LCD screen into it, via composite Video, which works ok and is quite bright. I dont have access to brightness/contrast, but since I set it up before I built it in everything is fine so far.

Someday when I find the time I will have a look at the damaged screen, maybe I find a flexcable that would fit. Hopefully it is going to work then...

Here´s my work of today as a summary:
http://www.flickr.com/photos/65709578@N06/12138988584/#

At least something! 

[thesteve]

T500 is a transformer, not a coil
It can fail like a coil and likely uses all 7 pins

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