Black screen on 7800

[Lars]

I just bought a used 7800 with original PSU online from a retro shop.

I couldn't test the console on arrival and stored it with my other consoles in my mancave in the basement.

Today I connected the 7800 with my (old) TV and received nothing as a black screen. TC channel is right, 2600 is working on this channel.

The basement is cold (around 12'C) but dry. I took the console to a warmer room in the house.

I left the console on power with black screen and after around 15 minutes Asteroids was on the screen. Now everything looked good.

Did the same again, cold basement a few hours, warmer room, black screen for 15 minutes, then everything is OK.

Any idea what could be reason for this?

Or is it a better choice to send the 7800 back to the seller and get my money back?

 

THX for your help.

 

[NIKON]

the fact that the unit works after warm indicates that there is a solder problem...metal expands in heat and that may be just enough to make the connecting on the PC board to allow it to work. 

 

you may need to reflow all the solder connections or at least the ones that are broken when the unit is cold.

[+Stephen Moss]

I agree that it sound likely to a bad solder joint, if you are getting a black screen rather than static that suggest it is at least reaching some state and powered.

I would start by looking at the reset and clock pin and ensuring power in getting the all the IC's and any of those missing can halt the system although it could be anywhere as a black screen does not really help to pin it down to a particular part of the circuit.

[Lars]

Thanks for your answers.

 

Since the 7800 was sealed I decided to send it back to the seller and got a refund.

 

I bought a different one on ebay and this one is working but have a not very nice looking PCB: Several repairs were done in low quality.

Maybe someday I will find a better one...