26 replies to this topic

[firstatari]

Just bought my first atari, never had one as a kid so I figured it was time to treat myself. Anyway it is a Vader model, and it doesn't appear to be powering up. When I turn on the power, there is no change on the TV. I've tested the power cable and it works fine. I have tested some of the areas on the main board to see if it is getting power and some areas are showing power. My problem is I don't know what I am testing on the main board or what I should be looking for. Any tips or pointers would be appreciated. I suppose it could be an RF problem as well but not sure how to test it other than switching the RF cord out, which I have tried. Thanks everyone, this is a pretty cool forum.

[bjk7382]

Are you using a switchbox or an coaxial adapter. If you just plug it into an RCA jack it will not show anything on the screen. This is because it sends both video and audio thru the same wire..

[firstatari]

I am using a switchbox. I actually bought 2 ataris with a bunch of games from this lady. The one 4 switch wood panel atari works alright when hooked up but the Vader does not.

[bjk7382]

It might be one of the chips on the mainboard gone bad. I had a heavy sixer with a burned out main chip. It would work but the fire button was being read as held down all the time. I replaced that chip and it worked. Not having anything on the screen might be the TIA (Telivision Interface Adapter) chip. My best guess would be a bad main board.

[bjk7382]

Now that I think of it, I fixed one of my friends Atari Jr. that had a power problem. Look at the socket where the power plug goes into the system. The one that I fixed I had to take the side off of the little box that the plug went into and one of the little metal connectors inside of there needed to be bent up to touch the adapter. One sign of this would be a very sloppy or loose power plug into the system. Also check the three connectors that go out to the RF wire.

[firstatari]

Alright I replace all 3 chips from my working atari into the Vader and still nothing. Is there any way to check or test the video feed RF end of the unit?

I did notice one thing but not sure if it is of importance. The chip in the attached photo was putting out a much lower voltage to that 3rd prong than my working atari. The Vader barely registered anything on the meter, just a tiny bit. Anyone know what that chip does?

Thanks for any help you can provide.

Attached Thumbnails

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[Christophero Sly]

If it is printed with "7805", then I think that is the voltage regulator, and that is probably your problem...but I'm not qualified to give you a definitive diagnosis.

[bjk7382]

I would have given up by now and sold it for parts on ebay. I don't know what that chip does but I do know it gets hot sometimes. That is why it is screwed to metal, to dissipate the heat. I modified my Jr. with an a/v mod before and that little part got super hot. It might be bad, you could look on electronics websites and maybe find another one. Since I have heard in the past the entire 2600 could be built from over the counter electronics, except for the TIA chip. If you can't find one I have one that I could desolder and send you. I have a six switch one though (probly the same). But it sounds like if you don't even get a flicker on the tv it still might be the little black box where the power plug goes into the system.

These are all just suggestions, I have fixed my friends before, but I am no electronics whiz by any means. I can solder and work an ohm meter like the best of us, but I can't diagnose electrical problems very well. Like I said in the beginning, maybe you can FIND a non working system on ebay to cannabalize the parts you need. Okay I have rambled on long enough now. I know I had a lot of headaches when I was trying to fix my heavy sixer. I know it can be frustrating. Good luck.

[firstatari]

I'm going to bring it by the big dogs and see what they think. Didn't know there was a good atari place in my area, Atari best electronics in San Jose. Thanks for all your help guys!

[Ian Primus]

That 'chip' is a 7805 voltage regulator. They don't fail very often, but they are very common parts. You can get them for a buck or so at Rat Shack (if they still carry them). Sounds like the system just isn't getting power. Try measuring voltages at the cart slot, and make sure that the power input jack is making good contact with both the power supply's connector and the board. Those things come loose a lot.

Ian Primus
ian_primus@yahoo.com

[CPUWIZ]

Ian Primus said:

They don't fail very often, but they are very common parts.

The 20 year old ones fail quite a bit.

[Ian Primus]

Quote

The 20 year old ones fail quite a bit.

Good point... Sometimes I forget just how old this stuff is.
I personally have only seen one Atari with a bad voltage regulator, but I'm sure there have been many more.

Ian Primus
ian_primus@yahoo.com

[firstatari]

The voltage at the cart slot is very poor. Only a bleak reading on one of the prongs. So what does this mean? I'm not really an electrician or anything I just try to work with basic reasoning so any leads as to what to check or what might cause a week power reading at the cart would help me a great deal. Little by little we seem to be making some progress. One again Thanks for your help.

[Ian Primus]

Yeah, if you measured the +5v pin at the cart slot and didn't get 5v, then it sounds like the power regulator is shot. It's a very common part, you should be able to get it at any good electronics store, or even Radio Shack. Try replacing it and see if it helps.

Ian Primus
ian_primus@yahoo.com

[Eduardo]

The "chip" in the pic as others pointed out is just the Internal Power Regulator, is not really a chip, it knocks down the power from 9v to 5v.

How to test the 7805:
(Reading text normal with legs at the bottom of it)
Left Leg = +9v
Mid leg = Negative
Right Leg = + 5v

How do you know if is shot? The right leg the one you circled in the pic should read +5v constantly, you should get a nice and steady reading at all times otherwise consider it done for.

I hope that helps.

[firstatari]

that does help. It reconfirms that the regulator is bad. I was getting under a 1v from that prong. Going to check the Shack on the way home tonight and see if I have any luck there.

Thanks.

[bjk7382]

Like I said before, i have an old six switch system that I could take that part out of. I could desolder it and send it to you for like .50 cents. That is if you can't find it at Radio Sack. (I call it that because I am not to fond of that place)

[bjk7382]

Nevermind, I just dug it out (bad system) and it works but it is reading too much on that voltage regulator. It is a constant 8.8 and it is drawing out wierd effects in the games. The colors are real messed up, the sound is horrible and you can see the game elements without playing. (i.e. you can see the bombs in kaboom without playing) So in the end I guess I can't help you out. unless someone can sat that 8v is okay. which I don't think it is.

[Ian Primus]

No... 8v is not OK. It sounds like you have a bad regulator as well... Fortunately, these are really common parts. I have bought them at Rat Shack before, and the do (or did) carry them. I also have several in my junk box, so if you really can't find one, let me know.

Ian Primus
ian_primus@yahoo.com

[bjk7382]

Mine was a bad system anyway. It is one of the chips on the motherboard. It reads every game as the button being held down all the time, even with no joystick. So I guess there is more than one thing wrong with that sytem. I had bought that one origianally to fix my heavy sixer. It was a working system until I swapped the motherboards to make my heavy sixer work. I got it really cheap and have been cannabalizing it for parts here and there.

[Ian Primus]

If it constantly thinks a button is being held down, it's the RIOT chip going bad. I ran into the same thing a few days ago, it was always going to the right. On the 4 switchers, the RIOT is the one just under the cart slot. I don't remember offhand where it was on the heavy sixer though, It's been a while since I have had to fix one...

Ian Primus
ian_primus@yahoo.com

[bjk7382]

I just bought a cheap regular six switch and swapped the motherboards. Even though the chips lift out, I didn't want to take the chance of breaking a pin off. Everything worked out fine and I now have a working heavy sixer.

there is a pic of my now working heavy sixer at this thread because it is made in taiwan

http://www.atariage....pic.php?t=36723

[firstatari]

thanks again guys. I stopped by radio shack and they do carry the voltage regulator but were out, I'm sure if I check another shack out they will have them. The kids behind the counter were having a hard enough time ordering pizza from the place 2 doors down so I did not want to bother them with checking their stock on the 7085 regulator. I'll update once I get the thing replaced.

[firstatari]

The Vader is alive. The 7805 voltavage regulator was the problem. Haven't soldered it in yet but did a preliminary test and viola! Up popped the game on screen. thanks everyone for all your help on this! Now just have to figure out how to eliminate the small amount of snow and static. Maybe just the RF adapter so I'll try a new one and see if that fixes it.

[Ian Primus]

Quote

The Vader is alive. The 7805 voltavage regulator was the problem. Haven't soldered it in yet but did a preliminary test and viola! Up popped the game on screen. thanks everyone for all your help on this! Now just have to figure out how to eliminate the small amount of snow and static. Maybe just the RF adapter so I'll try a new one and see if that fixes it.

Glad to hear you got it working. To help reduce the snow and static, just skip the switchbox and go for the RCA to F connector adapter. AtariAge sells them here at the store, but you can also get them at Rat Shack. This little adapter converts between the RCA conector at the end of the RF cable to a screw type connector to plug into the back of the TV set. It will give a sharper picture, since you'll get less interference. Those RF switchboxes leak RFI like a sieve.

Ian Primus
ian_primus@yahoo.com