Colecovision white screen with audio?

[Austinpatton16]

I just bought two 2 broken colecos, 1 i get a white screen with audio and the other i get a black screen with blue speck and garbage audio.

 

Atm i want to focus on the one with the white screen.

I put donkey kong in it and a white screen comes up and i press 1 on the controller and the normal music plays.

 

I have hard wired siwtch on so the switch is not the problem.

 

Nanochess in another thread said "You can connect directly a composite RCA to the video output pin of TMS9928 for testing directly VDP, a good VDP always generates synchro right for NTSC."

I wired this and a got a white screen, so i think we can rule outa bad vdp.

 

I tired benhecks composite mod and recieved the same white screen, so the rf box must work.

 

Any other things that i could test/be the problem?

Edited April 3, 2016 by Austinpatton16

[ColecoDan]

if you have the atari adapter and you can test that and you still get the same white screen then it has to be RF problem because the atari module blocks out everything except RF to play the games.

[Austinpatton16]

if you have the atari adapter and you can test that and you still get the same white screen then it has to be RF problem because the atari module blocks out everything except RF to play the games.

I don't have an atari adapter, but i have tested the vdp by getting a composite signal directly off the chip, bypassing the rf box entirely.

 

To clarify, i can use the controller and i can hear the game and it sounds like its playing fine(i hear jump sounds when i press jump) but i have a white screen.

Edited April 3, 2016 by Austinpatton16

[cdn2a]

If the game works where you can hear sound and such then you have removed more than half the trouble shooting. If its working the cpu, clock, sram etc is all good. That leaves VDP, video ram, RF board.

 

A composite cable into your tv and pin 36 of the vdp should show you a B&W picture. If it is garbled than it could be bad video ram.

 

The atari module will eliminate the RF portion.