A Maria problem?

[Brian R.]

I was getting my third 7800 console out for the serial number thread. It's actually my second in order of acquiring, but is packed away with good reason.

 

I put a new motherboard in this case back in 2007. It had problems, but I never was able to rectify it with the place I bought it from. The details elude me these many years later.

 

It hasn't spontaneously fixed itself.

 

What it seems it does - 7800 games will freeze or not start properly at all; 2600 games play fine. (Although I was able to play 7800 Ms Pac for a while without problem.)

 

So I'm guessing there's a problem with the Maria or some other 7800-specific part of the system. Any ideas or thoughts on what it may be? Some of you guys seem pretty tech knowledgeable, maybe you'll know right off what it is.

 

This board was probably reconditioned/serviced. Given that, I remain surprised that it never worked right.

 

Any thoughts?

Edited September 21, 2013 by Brian R.

[ApolloBoy]

I've got a feeling that it's not the MARIA chip. There's a couple of logic chips that control what mode the system is in (a 74LS174 and a 74LS32) and since those are easily replaceable I'd check those first. Failing that, it could be a bad trace.

[SoundGammon]

Could be a weak power supply, first thing I'd do would be to change the big filter capacitor at the back by the power plug. Caps dry out over time and lose their ability to filter the power or help regulate it. If any ac sneaks through it could cause lock up problems.

[Brian R.]

I'm fairly certain it can't be the power supply because I use it with another 7800 and it works fine.