Colecovision Black Screen Issue - Power Tested OK

[Smack2k]

I have a colecovision that is getting a black screen when powered on. I tested the Power Supply from where the plug attaches to the system as well as where the wires attach to the motherboard and got readings of 11.89V / 5.02 V / 4.89 V with the unit powered on.

 

What other issues can I look into to find my issue with this system?

 

I can check the voltage on the RAM chips, would that be a good place to look?

 

I could take a heat gun over the board to reflow the solder as well, not sure if that is a good idea or not?

 

Thanks ahead of time!

Edited March 16, 2016 by Smack2k

[Jeremy Popp]

I have 2 suggestions from previous experience.

 

#1 is cartridge slot - make sure it's clean and you're using a known working game.

#2 is to clean the whole PCB - I once had a unit with black screen, but was really dirty. After a good cleaning, it works every time.

 

Sorry if those are too obvious, I'm sure others can chime in with more technical answers.

[omf]

I have a colecovision that is getting a black screen when powered on. I tested the Power Supply from where the plug attaches to the system as well as where the wires attach to the motherboard and got readings of 11.89V / 5.02 V / 4.89 V with the unit powered on.

 

What other issues can I look into to find my issue with this system?

 

I can check the voltage on the RAM chips, would that be a good place to look?

 

I could take a heat gun over the board to reflow the solder as well, not sure if that is a good idea or not?

 

Thanks ahead of time!

see if a game that plays music instantly like boulder dash for example plays audio through the sound chip by hooking ip a speaker wires to ground and the sound chip output pin / trace

 

if you just get a tone consistently you may have bad ram (which is by the cartridge connector) which is what happened to me and my French board

i suppose it is possible you could have a bad logic chip somewhere

 

if you get the correct music playing then the issue to in the video logic and its either the vdp and or video ram that's dead

[Smack2k]

I am going to finally do some more testing on it today or tomorrow and check out both of your tips. I cleaned out the cart slot and cleaned the motherboard off a day ago, so that should be good.

 

I tested every RAM chip and they all have the right voltages on the right pins, and the power as I said before is good.

 

If this ends up being a bad game that I was testing with (I only had the one at the time) I am gonna be pretty PO'd at myself. But at least the system is completely clean..

 

Will let you know the results.

[Jinks]

Dont put a cart in then and power it on. It will say no cart inserted on the screen.

Probably your ram chips.

Hook up two rva cables one cable to pin 7 and other to 8 on sound chip and the other to the pin 5th from the end on the vdp and ground should get b and white video and sound.

I wish you the best of luck!

[Smack2k]

WIth no cart in and powered on, I get a black screen.

 

I checked my RAM chips and they all test well for proper voltages and other tests as seen is this page for RAM Fixes - http://console5.com/wiki/Colecovision_5V_RAM_Modification. The testing part at the bottom is what I was talking about, all my tests passed.

[pseudo_intellectual]

I had an identical problem which turned out to be the CPU SRAM instead of the VDP DRAM. If it helps, I documented my travails in another topic a few years ago (scroll down):

 

http://atariage.com/forums/topic/183844-colecovision-crisis/

 

If you can get one, a logic probe is useful to see if the CPU is doing anything useful on startup.