Is this Atari 7800 even worth trying to repair?

[+davidcalgary29]

56 minutes ago, ChildOfCv said:

Haha, I just noticed that someone signed his initials with the copper trace.

Cool! Those are my initials (but not my work).

[ChildOfCv]

51 minutes ago, livingonwheels said:

I tried a 2600 game and I get a grey screen with a light hum.

By the way, is the bolt and screw behind the cartridge slot supposed to be getting warm? I presume so considering I believe there is thermal paste on one side of it also.

Yeah that's where the voltage regulator mounts.  It does tend to heat up, though the amount of heat depends on load.

 

Well, anyway, are you able to reattach that missing trace?  If not, then it probably is time to find someone near you to fix it.

[livingonwheels]

Here's another view of the area that looked like it had a broken trace. It looks good from this angle am I correct?

I have a few av mods coming in later this week, and am thinking of installing one in this console to see if anything changes. 

Edited December 18, 2019 by livingonwheels

[ChildOfCv]

I don't know... I've never seen a solder pad mash out like that.  You should at least touch it with some flux and a soldering iron to see if it decides to behave.  Well even more important than that, make sure there is continuity between the two pads.

[+-^CrossBow^-]

8 hours ago, ChildOfCv said:

I don't know... I've never seen a solder pad mash out like that.  You should at least touch it with some flux and a soldering iron to see if it decides to behave.  Well even more important than that, make sure there is continuity between the two pads.

If that is the pad mashed out like that, then it also is likely shorting on the pin next to it as well. Either way, that needs to be wicked up, cleaned up, to see what is actually there. If the pad is gone as we suspect, then just need to run a short clipped lead off a component or piece of wire to reattach the connection to those pins.

 

[livingonwheels]

I'm getting continuity between all 3 pads there. That's not right, is it? The middle pad shouldn't.

EDIT: I cleaned up the area with a wick and no longer have continuity with the middle pad. But it still has not fixed the problem. I do notice though that if I move the channel switch on the 7800 to channel 4 (I've been using channel 3), it's even worse ( I change the channel on the tv to 4 too, of course). I get pretty much nothing but static. I'm guessing the av port is still an issue.

Edited December 18, 2019 by livingonwheels

[+-^CrossBow^-]

It is much cleaner and no you shouldn't have been getting continuity on all three. So it is good you cleaned that up to correct that. However, it does look like the pad is basically gone. Did you test and confirm you are getting continuity from pin 13 to 15?

 

If that is good to go, I believe you mentioned that you get basically a solid color screen when turning it on without a game inserted? And you get he random bars with audio hum or noise with a game inserted?

If the above is true, it means the cart isn't making good contact in the cartridge port still with the contact pins. Could also be other issues causing this but that is usually what it means.

 

Which games have you tested with this console so far?

[livingonwheels]

Yes, I am still getting continuity only between 13 and 15 now. It's pretty disappointing that that didn't fix the problem. I'm hoping that when I do the av mod later this week, a miracle will happen.

It's pretty random what I end up getting on the tv, I've used a variety of 2600 carts, and mostly Crossbow and Foodfight for 7800. All games get the same results. Here are some pictures I just took as examples. The first 3 tv pics are on channel 3, the last 2 are channel 4.

 

[+-^CrossBow^-]

The first TV pic...which game did you use to get that image?

 

[ChildOfCv]

Well, one possibility is that there is an unwanted load within the AV box due to whatever got gunked up inside, which may be depriving the rest of the system of its power.  I guess an important question that we haven't bothered to ask yet:  What are the actual voltages in the system? For example, the voltage between this circled point and the shielding ground?  Also, without power connected, what is the resistance between those two points?

 

 

Anyway, as rusty as that box is, maybe you should go ahead and remove it now, then pop the bottom off and see what might be inside there.

 

 

[livingonwheels]

I'm unsure which game gave me that image, but for some reason I've been unable to replicate it with the same carts that I used for those pictures (Galaga 2600, Pacman 2600, Crossbow 7800, Food Fight 7800). It's like when you press the power button you never really know what you'll get on your display.

I'm getting 10.5 v on those 2 points.

Resistance 76

Edited December 18, 2019 by livingonwheels

[ChildOfCv]

4 minutes ago, livingonwheels said:

I'm unsure which game gave me that image, but for some reason I've been unable to replicate it with the same carts that I used for those pictures (Galaga 2600, Pacman 2600, Crossbow 7800, Food Fight 7800). It's like when you press the power button you never really know what you'll get on your display.

I'm getting 10.5 v on those 2 points.

Resistance 76

Replace the regulator, NOW.

 

You should only see 5V at most, with only a couple of exceptions.

[livingonwheels]

I think I made a mistake. I get 5v when I have the multimeter set as below. I got the 10.5 when the dial was set on the red 200.

[ChildOfCv]

On the black (DC) side, 5V is good.  But it should be near zero on the red (AC) range.  Are you sure you didn't misplace the decimal point?

[AtariLeaf]

So was thing dropped in the ocean?

[livingonwheels]

I just double checked on 200 red (ac). It's definitely 10.5.

The shielding has rust holes through it (one rather large), so it might have been submerged for awhile. Most of the screws holding the case together were gone, and the one that were there were not the correct size screws either. 

As long as I'm going to do the av mod, I might as well remove the rusted av box as suggested.

[livingonwheels]

No turning back now:

[ChildOfCv]

By the way, did you verify the traces that Crossbow mentioned on the first page of this thread?

 

Anyway, with your meter on the red 200, I wonder what it would read from a 9V battery?  Maybe the meter just doesn't properly isolate DC voltage on the AC settings.

[livingonwheels]

Yes, in Post #31 you'll see that I took care of it and now have proper continuity.

Using a 9v battery I get 9.5 on black 200, 20.3 on red 200.

As seen on the pic above, in Post #42, the av box actually looks quite clean and rust free. I'm a little concerned that the av mod I'll be doing later this week (as soon as my kits arrive) may not make a difference.

[+-^CrossBow^-]

That is why I was asking about which game you got that first TV pic with. Because that pic looks to show like some game data is trying to be displayed but would also point more towards an issue with one of the ICs. Since you aren't getting anything currently, the VR should be replaced anyway as the originals are known to be quite faulty on the 7800. (Likely not spec'd right for the console to begin with), and then start with the 6502C CPU. If you get it back to what you saw in the first TV pic, then it might be the RIOT chip at fault to try first.

 

I know it appears to be a shot gun approach as this point and it largely is. But given that you aren't getting any real change on the TV when powering it on, or at least one that helps isolate further it is the only thing we have to go on right now.

 

Also you did verify that those pads I circled on the first page are good? Again, they looked as if they were lifted from the board in that pic due to the shadows under the pads that matched the size of the pads.

 

 

[ChildOfCv]

24 minutes ago, -^CrossBow^- said:

Also you did verify that those pads I circled on the first page are good?

I just asked about that myself

 

 

At least that solves the lingering doubt about the meter.  Apparently it gets confused if there's DC on your AC readings.

 

To get a good look at the RF board, you'd have to desolder the pin from the board to the output jack, and there's also a blob on the board that holds it to the case.  If you can do that and look at the back of the board, that would confirm the condition of video output.  But you're likely right that that is not the issue.

 

RIOTs are easier to find than 6502C's though (note:  NOT 65C02).  So if you are stuck with shotgunning it, you could start there.  Intelligent troubleshooting may require more expensive probing tools.

[livingonwheels]

I installed the AV mod, but there is no difference. Same symptoms that I had previously with it's rf. Sounds like my next step will be to replace the riot chip. My tools are not good enough for that, so can someone link me to a good set of tools that I could use to remove and replace the chip(s). Below is pictures of my soldering station (which is probably good enough for most jobs) and my desoldering gun/pump (which never seems to even get hot enough to even melt the solder). 

 

Edited December 23, 2019 by livingonwheels

[ChildOfCv]

Probably the best option is a desoldering tool.  https://www.amazon.com/American-HAKKO-Products-FR301-03-Desoldering/dp/B07BFVFMS9

 

But if you prefer not to spend that much, you can just get solder braid and flux.  Perhaps finish it off with a single-shot pump like this.  https://www.amazon.com/Engineer-SS-02-Solder-Sucker/dp/B002MJMXD4

 

You can search Youtube for through-hole desoldering techniques.

[livingonwheels]

 I found that same tool on eBay for $277 

https://www.ebay.com/itm/New-Hakko-FR301-03-P-Desoldering-Gun-Tool-FR-301-Replaces-FR-300-FR300-05-P/171356976966?epid=10030647862&hash=item27e5abf746:g:xTsAAOSwDOpb21U2

 

I’m going to purchase it, it’s about time I got some decent tools. I might even be able to write it off on my taxes by implying that I need it for repairs around the house.

 

You figure that I should start with replacing the riot chip? Is that the 6532 chip? Do you have a good source for these chips? 

[ChildOfCv]

Yeah the 6532.  Look on eBay   Just beware that some come from China.  So even if they work, they may take a while to arrive.