Ianr757 Posted May 20, 2021 Share Posted May 20, 2021 I just got in a nonworking Colecovision that I thought I'd try and repair. Upon initial inspection, the console would power on, but the screen was black and there was a hum/sustained beeping noise every other power cycle. I tried the Atari expansion module and it worked fine, so I thought it was going to be either the RAM, VDP or both. Well, after replacing all RAM ICs using the 5v memory mod, and the VDP with a spare, it still has not improved. Any ideas of where to go next? Thanks! Quote Link to comment Share on other sites More sharing options...
Ruggers Customs Posted May 20, 2021 Share Posted May 20, 2021 You check the cpu? Normally I would say power supply first but I assume you've checked that already. Black screen with a tone is either going to be your cpu and or the vdp most of the time. Quote Link to comment Share on other sites More sharing options...
Ianr757 Posted May 20, 2021 Author Share Posted May 20, 2021 8 minutes ago, Ruggers Customs said: You check the cpu? Normally I would say power supply first but I assume you've checked that already. Black screen with a tone is either going to be your cpu and or the vdp most of the time. Aha, I was leaning towards the Z80, just didn't know if it would make a difference since the expansion module works. Thanks for the tip! And yes, the power supply is just fine, so it must be the Z80. I'll swap it out and report back. Quote Link to comment Share on other sites More sharing options...
Ianr757 Posted May 20, 2021 Author Share Posted May 20, 2021 @Ruggers Customs Success, it's alive! Turns out the original VDP was fine, just the Z80 and maybe the RAM (which was going to be modified anyway). Thanks so much for the help! 1 Quote Link to comment Share on other sites More sharing options...
Ruggers Customs Posted May 20, 2021 Share Posted May 20, 2021 22 minutes ago, Ianr757 said: @Ruggers Customs Success, it's alive! Turns out the original VDP was fine, just the Z80 and maybe the RAM (which was going to be modified anyway). Thanks so much for the help! Awesome, good job! Quote Link to comment Share on other sites More sharing options...
CrazyBoss Posted July 13, 2021 Share Posted July 13, 2021 if its the VRAM it will still give you a "boot screen", but it can have problems like wrong text or damaged graphics, not sure if the "main" ram is bad, for Colecovision (and all other tms99xx systems) its normaly the VRAM that goes bad. Quote Link to comment Share on other sites More sharing options...
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