Turboexpress LCD mod take 2 - rolling screen

[wilykat]

LCD screen tested good when I used other devices but when I connected to the TE, the screen rolls very slowly. Like 2 seconds for one full flip.  This is what I am using for wiring: https://www.tapatalk.com/groups/pcengine/express-gt-composite-t179.html

Any idea? It seems the sync should be within the video but the sync seems off.  The LCD is supposed to be auto sensing NTSC and PAL so it may be the sync is not present?

[DeshDildo]

Did you retest the screen with other devices after the rolling problem?  I only ask because I tested a screen then installed it in a Nomad and had the same issue.  I retested with another video source and found it had the same issue still.  Ended up getting a different screen and all was good.

[thesteve]

some of the screens do that on PCE/TG16 sources only, so test it on a home console with same chipset, test your mod on a different screen/TV

[Keith Courage]

It's a bad screen/board. Not compatible with PCE. I've had that issue many times. Took a bit until a found a few different sources with good screens.

[wilykat]

so the seller that I got a good LCD the first time is now sending shit screen the second time? On the outside both looks the same and came in the same box.

Wish I hadn't fried the first one.

[thesteve]

the issue is the panel not the board, so you might be able to combine

[pnauts]

which sync signal do you use ?

[wilykat]

which sync signal do you use ?

Should be built in.  I hooked my TE to a TV and it was fine. The LCD seems to be bad out of the box.

[thesteve]

the issue isnt the sync, so much as the line count
the LCD screens have a fixed line count and some of the display panels reject V-Sync before last line causing either rolling or picture freeze depending on which panel

[wilykat]

Then that panel would never work with Atari 2600.  It had an unusual video design, leaving up to the game to accurately keep track of v and h sync timing.  Not all games followed 262 lines (including v-blanking) per field rule.

[thesteve]

never tried atari on one

[pdiggitydogg]

Fwiw, I am having trouble getting a good LCD for my Sega Nomad as well. Sounds like we're having the same issue with cheap lcds... I am on my third attempt, ordering one from dealextreme. If it works, you may have luck with it as well. I'll try to remember to check back.

[wilykat]

The first 2 I got were from hottestdealever.  The first one worked well before I ruined it. The second one looked different internally and I couldn't get it to work, I don't know if the seller got a bad batch or if I got something that was a customer switched-and-returned junk. The seller refunded me on the second one for being shit so I still have shit screen and not a damn thing I can do with it.

The third one I am waiting on is from bin361 (auction 181529434603) that KC suggested to me in a PM.

I think the main issue is digital design.  It's more touchy to nonstandard rule while older analog design were more relaxed and worked with wider range of timing variations such as extra lines or fewer lines in a single field.  It's mainly this reason a few really old consoles don't work well on modern TV.  analog LCD panel are rare and, most likely being old stock, won't have the same image quality as modern LCD.

[thesteve]

the digital panels have a line driver chip in the ribbon
there are a few different driver chips, some are flexable some arent

[wilykat]

Take 3 worked and this time I took precaution not to fry the LCD controller board

[thesteve]

now the first one may be fixable

[wilykat]

Nope.  The LCD off the first one is still fine, the PCB is still dead.  Too many tiny SMD for me to work with and not worth saving $15.  I am keeping the extra LCD as spare.