Colecovision and vertical lines on left edge of Sprites

[RTBaker]

Hi,

 

I have just spent a few weeks bringing an old ColecoVision back from the dead. It was a flea-bay purchase and had a dead power supply, faulty video memory, a dodgy power switch and a broken cartridge connector!.

 

Anyways, I have replaced the memory - now 5V only, repaired the power switch, replaced the cartridge connector and it now runs OK from a 5V power supply with a 5V to 12V (Pololu U3V50ALV) up converter inside the case.

 

The problem I now have is that I am getting vertical lines on the sprites as shown in the attachments. Its fine when the games startup in text mode but appears as soon as a sprite is present.

 

I have attached some photos of the problem.

 

Can anyone help and point me in the direction of the problem please?

 

Thanks very much for your help.

 

[R.Cade]

Looks like a stuck bit in VRAM.

[+-^CrossBow^-]

Was going to say something similar. Since you upgraded/replaced the vram. Double check all of your connections and traces. I won't lie, I killed 2 other CVs before I was successful in doing the +5 ram upgrade. The damn traces just come up so easily and damn near impossible to track down and fix after the fact.

[RTBaker]

Thanks for the advice - I'll try to double check all the traces with a multimeter to check continuity between all the VRAMs

[7800fan]

I hope you made those RAM socketed, if you soldered the RAM and you had to resolder, you risk more damage to the fragile traces.

 

When I did my mod, I used my meter and tested from the top of the chip's pins so I could both verify the connection is good and to find bad trace or just bad socket connection. All of the address lines are the same but data lines are separate.

 

A lot of probing but saved me the trouble later on when I found a couple broken connections.

[towmater]

F18A time now is here. I would hope one would solve all of your problems as it has it's own video ram.

[RTBaker]

I did put in sockets so I was able to check out all of the memory lines between the memories and to the graphics chip - they were all OK.

 

I then thought to check out the power supply I was using and found that it tops out at 500mA so I changed it for the 1.5A unit I use with my Raspberry Pi.

 

With the new power supply all is well and all of the lines have disappeared!

 

Thanks very much for all the suggestions and help

[DadsGlasses]

Seems like "Power Supply" is the solution to almost all ColecoVision problems! Glad you got it worked out.