PCEGT replace with 3.5inch TFT LCD

[thesteve]

i use a second drive circuit for my AV out, because the stereo AV out shorts the vid pin to ground when using a headset.
my drive circuit is designed for it
i use a 1k resistor from the first transistor emitter (screen out) to the AV transistor base
220 ohm from 5V to collector , emitter out
during emitter ground, the 1K keeps the video good, while the 220ohm keeps the transistor safe

[Duo_R]

if the headphone jack was replaced with a true mini AV out port a 2nd NPN wouldn't be used correct? I would think the same Video line could be split to screen / AV out if there wasn't a shorting issue. I have one of those exact ports that I can use.

[turbokon]

You would still need the 2nd transistor.  If you plan to use the stock LCD, then you would only need one.  Where did you get this port you're planning on using?

[Duo_R]

I sourced from another device, probably a DVD player can't remember.

[Duo_R]

out of curiosity is anyone testing these on Turbografx / PC Engine / Duo systems prior to opening them up? Do they also display the white screens on those systems?

Hey thesteve, do you have a solution for the all white screens yet?

Thanks!!

[turbokon]

That wouldn't be a bad idea. Chances are if they work on a duo/tg16/pce setup with comosite out then it will work with the TE LCD mod.

[Duo_R]

Exactly that way if you get one that doesn't work you can ship back.

Just need to get an external power supply to boot the screens up.

[turbokon]

I use your TE battery mod as the power source when I'm testing these LCD.

[Duo_R]

Nice

[thesteve]

yes i was testing on the TG16
same results

[pcengin4eva]

I did the mod so far ... i liftet 19 25 29 32 39 and grounded them . I connected 20(CB)to 27k ,26(B-Y)to8.2k ,33(R_Y)to6.3k and 40(Y) to4.7k ( i didnt lift any of those pins) . Afther the resistors i connected all of them to BASE of a BC337 NPN transistor (on whichs Collector 5v from the upper side , measured and ok) . Emitter goes to 75 ohms and after that to the lcd´s video in . LCDs GND goes to GND naturally . All i get is a very weak picture .

Whats wrong ? Wrong transistor ?

[turbokon]

I did the mod so far ... i liftet 19 25 29 32 39 and grounded them . I connected 20(CB)to 27k ,26(B-Y)to8.2k ,33(R_Y)to6.3k and 40(Y) to4.7k ( i didnt lift any of those pins) . Afther the resistors i connected all of them to BASE of a BC337 NPN transistor (on whichs Collector 5v from the upper side , measured and ok) . Emitter goes to 75 ohms and after that to the lcd´s video in . LCDs GND goes to GND naturally . All i get is a very weak picture .

Whats wrong ? Wrong transistor ?

You sure you're getting 5v to the transistor? Maybe the LCD you're using doesn't work well with 5v.

[pcengin4eva]

No 5V go to the NPN Collector of the Composite signal

Ipowered the LCD with external 9V for testing . It works perfect with my CoreGrafx Video signal . But not with the TurboExpress Composite i created

[turbokon]

No 5V go to the NPN Collector of the Composite signal

Ipowered the LCD with external 9V for testing . It works perfect with my CoreGrafx Video signal . But not with the TurboExpress Composite i created

Where are you tapping 5v for the transistor?

[pcengin4eva]

Where are you tapping 5v for the transistor?

From Q502 collector , upperside , measured 5v with multimeter and ok