new guy, probably the same old problems

[GarwoodGideon]

I'm an old Gamer, looking to get back into Atari, so I bought a tele-games heavy sixer off ebay for like $30, I plugged it up, it works fine until about 3 minutes after I start playing, at that point the screen starts to fade and become extremely dark, still visible, but barely. I had taken it apart and cleaned all the major components, with alcohol, microfiber cloth and detailing brushes, and also cleaned up the connections in the cartridge slot, RF cable port, etc. I have also ordered a new RF cable, in case that's the problem. I just thought I'd throw this up in case this is a pretty widely know issue that I can save some time troubleshooting by drawing on the experience of those more seasoned in these regards. Let me know what you think, and thanks for listening to my ramblings.

 

GG

[fujidude]

First off, hello there! Welcome to all things Atari and retro gaming/computing. Since the machine consistently operates when 1st powered on for a few minutes, it suggests to me either an excessive heat build up situation or capacitors that have started drying up and are drifting too far out of spec, especially when warmed up. Since you have taken it apart and cleaned it, I'm sure a blanket of dust or the like isn't an issue to heating. And as long as you are not running next to a heating register or blocking all the machines ventilation, I'm guessing it's not an over heating issue. That leaves caps. You can look for signs of bulging etc., but caps don't have to have bulged or burst to be unusable. Another thing you can do is check for any chips that get too hot after the machine is on a little. My understanding is that for the most part, chips that have no heat sinking for normal operation should not burn you finger if you touch them. Also, it would be wise to check the output of the power supply to make sure it's within limits.

 

I'm not an electrical engineer, nor do I have experience repairing Atari VCSs, so keep that in mind when weighing the value of my advice.

[+Stephen Moss]

Could be the voltage regulator going into thermal shutdown which would reduce its output voltage.

 

If you have access to a volt meter/DVM first check the output of the power unit when disconnected from the VCS, if it is an original (or replacement) unregulated unit it should read around 12 - 16 volts DC, if it is a regulated replacement it should read 9V DC.

 

Next read the output voltage from the power unit when it is connected to the system but the system is off (try reading it at the power input connector), if all is well you should read about the same voltage as before.

 

If the result of the first two tests appear to be satisfactory then switch the unit on and check the output from the power unit and both the input and out voltage of the voltage regulator (LM7805) which looks like a black box roughly 6mm x 6mm x 2mm with a metal tab sticking out the top and 3 legs sticking out the bottom (probably mounted flat to the PCB and labelled VR1). The centre leg will be ground (0V) and the other two will be the input and output voltage.

All being well the output voltage of the power unit/input voltage of the regulator will drop to around 9V DC (if unregulated or remain at 9V if regulated) and the output of the voltage regulator will be around 4.5 - 5.5 V DC, if so measure these voltages again when it starts going wrong to see if they are the same or have changed.

 

NOTE: In regard to the previous post if working correctly I would expect the voltage regulator to be the only component getting noticeably warm under normal operating conditions (best to avoid touching it).