PC Engine GT Dim Screen after Cap replacement

[Slypty]

So I bought a Cap replacement kit and replaced the Audio and Video Caps.  As far as I know, the Audio Caps are 4 in total, but the Video Cap is only 1.  That's all I replaced, but the lighting on the Screen still seems a bit dim, especially if you're not looking directly vis-a-vis with the screen. 

  So if I tilt the screen at a slight angle, everything seems to go dimmer.  Not sure if this is still a cap issue, or perhaps my batteries aren't juiced up enough.  First time fix and I've got powerful sound coming from the Speaker now with all 4 Caps replaced, and over-voltage (6.2 as opposed to default 6V if I remember right.) 

  Are there any other Caps that deal with the Video, or is it just that one on the corner.. I don't remember the volts or farads for it, sorry.

[Slypty]

I see from an earlier post that this might be an LCD backlighting issue.. if I can twist anyone's arm to let me know which Caps deal with the backlight power.. well I would be gobsmacked.

[thesteve]

Backlight caps are the 16V 100uf caps by the video cap

[Slypty]

Thank you!  Now to tackle the foamy junk around those caps. 

[thesteve]

Be careful its hiding an inductor

[NightWolve]

Since you got it open and got the hang of desoldering surface mount caps, you should just replace all caps and be done with it. Every last one of my TE caps had leaked and I'd wager you noticed leaky ones as well... There's no sense in running the system with some caps new and good, while the rest are 24+ years old, likely leaky and are thus operating at a much lower capacitance capability potentially risking permanent damage... The fluid from leaky caps does corrode traces over time, so FYI.

[Slypty]

Since you got it open and got the hang of desoldering surface mount caps, you should just replace all caps and be done with it. Every last one of my TE caps had leaked and I'd wager you noticed leaky ones as well... There's no sense in running the system with some caps new and good, while the rest are 24+ years old, likely leaky and are thus operating at a much lower capacitance capability potentially risking permanent damage... The fluid from leaky caps does corrode traces over time, so FYI.

  Well it's laziness at its' finest.  I really should and probably will do the whole thing, but I'm more interested in solving the current issues before I do a complete overhaul.

  I changed the backlight caps mentioned earlier, beside the known video smaller cap.  I broke a trace but mounted it to another place on the trace, and got both of those f'n annoying caps replaced... only problem is, there's no difference.

  I'm not sure what type of problem this is now.  If it was a backlight problem, I wouldn't have a backlight.. but I do.  If it was a video problem, I wouldn't have video, but I do.  I've seen other PC Engines or TE's and when looked at from an angle, there's still no dimness... whereas unless you're looking straight on parallel with my screen, the screen isn't visible otherwise. 

  I'll replace all the other caps later on, but if anyone has some insight to why this might be, it's very much a big help to me.  Thanks.

[thesteve]

Strait on or parallel
Does the contrast wheel work?
If the viewing angle is right, but the pic weak dark, it could be a bad lamp.
Low batterys is white pic
Bad caps is no pic or bad view angle

[turbokon]

I think the controller board could have something to do with it.  I had a TE I worked on where it had the same issue after replacing the caps.  Switched out the onboard controller board and it worked fine.


Sent from my iPhone using Tapatalk

[Slypty]

Strait on or parallel
Does the contrast wheel work?
If the viewing angle is right, but the pic weak dark, it could be a bad lamp.
Low batterys is white pic
Bad caps is no pic or bad view angle

  Jeez.. I hadn't even bothered fiddling with the Contrast wheel.  It's my first PC Engine GT, and I really hadn't even noticed it was there.  Anyways, I think it's working fine, I still get a worse picture depending on the angle, but with adjusting the contrast the angle is still pretty visible... I'm guessing that's normal?  I can't expect to see the screen the same from any angle... can I?

[Keith Courage]

It looks different from every angle much like older laptop screens. As long as you can look straight at it and get a good clear picture by adjusting the contrast then all is well.

[Slypty]

Weird, now after I had the contrast working for about 10 minutes, its' suddenly decided to crap out on me.  I'm not sure if it's just the batteries are too drained, but games are suddenly shutting off after a minute of playing.  I can make it shut off really quick if I start fooling with the Contrast wheel, which is suddenly not responding.  It worked fine and seemed to fix the earlier problem fine..

 So does the Contrast wheel bug out when the batteries are low, or is there another problem potentially with the caps or control board?

[thesteve]

Yes contrast doesn't work on low battery

[Slypty]

OK, thanks I'll take out the crapola PC plus batteries I spent $2 on, and use something with more juice.  Should be OK after that, thanks all for the good help

[NightWolve]

Ah, so you didn't know about the contrast wheel. Heh. Well, the other thing is test it with the power supply or do you not have one ? Batteries drain fast and yeah, it shut downs when there isn't enough juice. Unfortunately, there are still no good rechargeable batteries. NiMH still suck and they run at 1.2 V not 1.5 V like standard one-use alkalines and the industry hasn't yet made Li-Ion types in AA or AAA form. Maybe they can't at those sizes. That would be a good mod for the system actually, force a 7-9 Volt Li-Ion battery in there by destroying the plastic that holds the AA batteries if you have to and design a circuit where its recharged when the power supply is plugged in.