PC Engine LT with No Backlight - Help Needed

[mbrayf]

Good Afternoon All,  I have a LT which is working great apart from one thing... the backlight has ceased to work, which is causing a few headaches. If anyone has had this problem before or knows how to fix, I would be very grateful. I am a newb here so please be gentle (sunteam_paul recommended this forum, so thanks go out to him in advance).

[mbrayf]

OK, as no one seems to have had this problem before, is there anyone who can point me to a guide to taking the screen apart to get at the bulb to test it???? I would have a go blind but I am scared of buggering up my working LT.

[kid_rondeau]

Dude, I WISH I had an LT to have a problem with...I think that those of us who are fortunate enough to have one probably wouldn't want to take them apart if we didn't have to. I wish you luck in your search though.

[Duo_R]

sounds like a vid cap fix to me. See Nat's post if you want to DIY:

https://www.pcengine-fx.com/forums/index.php?topic=5015.0

[mbrayf]

sounds like a vid cap fix to me. See Nat's post if you want to DIY:

https://www.pcengine-fx.com/forums/index.php?topic=5015.0

Thanks for the advice... but the screen is working as it was designed, if you shine a torch on to it apart from blinding you the grafx are all present and correct, just no backlight. 

If this cap replacement will cure this (verification needed) i will do it with pleasure and post pics of the before and after...

[chop5]

ive seen very little info on the backlite bulb. some on assemblers site where he shows it taken apart. Post some pics if you can. this would be a good oppurtunity to start a info/tutorial.

[nat]

Yeah, unfortunately my fix won't restore a dead backlight. I've never seen one go out before-- so not sure on the proper repair procedure. Sorry.

[Duo_R]

I wonder if this screen can be LED modded, which would improve battery life.

[mbrayf]

Right, as soon as i get a full day free of distractons i will have a go at stripping the LT and finding the back light culprit. Photo's will be taken and if i fix it they will be posted (on the other hand if i bugger it up they will be burned and i will deny ever having attempted it).   

And thanks for the honest messages and i will keep you all appraised.

[mbrayf]

right, I have taken the LT apart and found that the backlight bulb is broken. 
If anyone can help with a replacement or source for one it would be appreciated.
PS pics to follow.
Right, more details....
the bulb is a w shaped ccfl tube which is 90mm tall and 55mm wide (all outside measurments) the center of the w only goes down 82mm not the full 90 of the two edge pieces.

[mbrayf]

pic as promised...
/dsc003712na2.jpg
/w389.png

[kid_rondeau]

Shit dude,
that looks like it's going to be very hard to replace as is...what is it? Is it a 12V lamp or is it LED-based?

...I was expecting a normal lamp of somekind. But who knows? Maybe someone knows where to find one!

[mbrayf]

Yeah, I know what you mean... it's actually a Cold Cathode Fluorescent Lamp and that PCB you see connected to it is an AC inverter giving about 350volts which is needed to energize this type of tube. this is one of the reasons i was reluctant to open the unit, and defiantly didn't power it when open.
On a foot note, the cable to this only carries 6.5volts DC, so that inverter is an impressive piece of engineering.

[kid_rondeau]

Right right, an impressive inverter indeed...is the transformer on the flipside of that PCB? If the electronics are working properly it might be possible to find just the bulb...but there's no telling how much that would cost.

If the bulb is removable, try taking it out and powering up the device and checking for 350VAC out of the socket...well, of course only if you know what you're doing, and if you're not afraid of being exposed to it.

It should be a substantially low current, though, not enough to cause any serious injury. I still wouldn't go making out with it or anything.

[mbrayf]

it is just the bulb that is broken, check out the bottom right bit of it in the picture... and yes I can remove it from the pcb as it is just one wire at each end.

[Duo_R]

first be careful, these circuits can store power and you can get shocked. 2nd - I would either attempt an LED Mod but with no diffuser that is going to be tough to do and make it look right. The second consideration if u can't find a bulb is to replace with a new screen altogether.

[mbrayf]

there is a diffuser on the back of the lcd (looks like a sheet of milky plastic). I was thinking of a lcd mod myself, do you have anywhere that I can find information on this and will the 6.5v off the main board be able to drive it???
all assistance is greatly appreciated.

[agt_dale_cooper]

350V?  WTF?  Suggest pulling the bulb if you can (is this wire holding it in place soldered?), inspect ALL SIDES for possible part number / specs (have you done this / is this where you got the 350V figure?)

Gonna see if I can't enlist some assistance here....mailed text of this post to sales*ccflsurplus.com for hopeful conversation...

I've had a brief look about, and apparently Sega Game Gear units use this same CCFL style methodology...got one you can tear down to have a look?  MIGHT just have the same setup...roughly the same era, isn't it?  That would be stupid cheap to sack a GG unit for it's bulb., they abound at flea markets..

[mbrayf]

thanks for the info and the suggestion of the gamegear (i had completely forgoten about them, or is it blanked them from my memory). And as for the voltage, I was going by the rating on the transformer and info off the net for the size and type of tube fitted.
Thank you for all your help, it is appreciated and welcomed.