Atari 7800 will not play 2600 games, freezes on 7800 games

[Officepot]

I have an atari 7800 I completed an AV mod on. I am pretty sure it works fine before I did the mod? This could be wrong though. I have also recapped and put a new 5V regulator onto the board. Now if I insert a 2600 game I get a random display of lines and a loud buzzing noise. The colors and amount of lines changes between taking the cartridge out and reinserting it. If I play a 7800 game the console will work fine at the menu screen. As soon as I start the game it will freeze after about 2-3 seconds. I cannot seem to get the reset button to do anything at all, pressing it does not seem to do anything. I have attached a photo of what my board looks like. I cut out the top left corner for my composite connections. I assume this is some type of chip issue? But would love some guidance if anyone has any advice. Thank you all!!!

Edited July 28, 2023 by Officepot

[+Mitch]

Which mod did you do? I don't see any pictures of it, just the main 7800 board with some wires coming off of it.

 

Mitch

[+Stephen Moss]

2 hours ago, Officepot said:

I have an atari 7800 I completed an AV mod on. I am pretty sure it works fine before I did the mod? This could be wrong though.

Well if you are not sure whether or not it was working correctly before you installed the AV mod, I would think the first and logical thing to do would be to remove the mod, restore it back to how it was and then see whether or not it is working correctly.

If it is then either the mod itself has a problem or you installed it incorrectly, if not then it would be better to get the base console working first before installing the mod.

[alex_79]

42 minutes ago, Stephen Moss said:

...restore it back to how it was...

That would be easier if the part of board coming out of the RF shield wouldn't have been snapped off...

 

I saw that "technique" in the installation guides from the site linked below:

https://vintagegamingandmore.com/guides/mods/

 

Breaking the RF modulator is not the only totally unnecessary and destructive step in those guides (there's plenty of space to solder the wires after just desoldering or clipping the pins connecting it to the main board, which makes it possible to restore the console in its original form).

e.g. the guide for the 6 switch Atari 2600, says to remove the bottom part of the shield and "throw it away". This leaves the main board hanging only connected by to screws on one end, with the other end (the one with the cartridge port!) without any support. The board will flex each time you insert and remove the cartridge which will cause cracks in the solder joints over time.

 

Unfortunately those guides come up among the first results for "atari video mod" in search engines, which causes many poor consoles to be modded raped like that.

 

 

Edited July 28, 2023 by alex_79

[+DrVenkman]

7 hours ago, Officepot said:

The colors and amount of lines changes between taking the cartridge out and reinserting it. If I play a 7800 game the console will work fine at the menu screen. As soon as I start the game it will freeze after about 2-3 seconds. I cannot seem to get the reset button to do anything at all, pressing it does not seem to do anything

Setting aside any possible issues with your AV mod, the symptoms sound like a bad TIA chip to me. Unfortunately, it looks like yours is soldered in, so that adds a wrinkle to any repair process if that is in fact the problem. 

[Officepot]

5 hours ago, alex_79 said:

That would be easier if the part of board coming out of the RF shield wouldn't have been snapped off...

 

I saw that "technique" in the installation guides from the site linked below:

https://vintagegamingandmore.com/guides/mods/

 

Breaking the RF modulator is not the only totally unnecessary and destructive step in those guides (there's plenty of space to solder the wires after just desoldering or clipping the pins connecting it to the main board, which makes it possible to restore the console in its original form).

e.g. the guide for the 6 switch Atari 2600, says to remove the bottom part of the shield and "throw it away". This leaves the main board hanging only connected by to screws on one end, with the other end (the one with the cartridge port!) without any support. The board will flex each time you insert and remove the cartridge which will cause cracks in the solder joints over time.

 

Unfortunately those guides come up among the first results for "atari video mod" in search engines, which causes many poor consoles to be modded raped like that.

 

 

Yes, this is the website I used for the guide and the same composite mod used. I have another 7800 I was going to attempt to mod and will refrain from breaking off the RF portion on that one.

 

57 minutes ago, DrVenkman said:

Setting aside any possible issues with your AV mod, the symptoms sound like a bad TIA chip to me. Unfortunately, it looks like yours is soldered in, so that adds a wrinkle to any repair process if that is in fact the problem. 

Thank you DrVenkman, after some research I had a similar conclusion. I have the ability to solder a new chip in (hot air gun / desolder station) are these TIA chips accessible at a reasonable price somewhere?

[+DrVenkman]

4 minutes ago, Officepot said:

Yes, this is the website I used for the guide and the same composite mod used. I have another 7800 I was going to attempt to mod and will refrain from breaking off the RF portion on that one.

 

Thank you DrVenkman, after some research I had a similar conclusion. I have the ability to solder a new chip in (hot air gun / desolder station) are these TIA chips accessible at a reasonable price somewhere?

The only source for new old-stock is Best Electronics and they can be … difficult to deal with (search the Forum for details). New NTSC TIA chips are also now about $50, which seems insane to me but it is what it is. Other than taking a crapshoot on eBay or AliExpress, your best bet might be looking for cheap, working 2600 and salvage the chip from that one. All Sixer models and many 4-switch woody models are socketed, which might make chip removal a little easier if you find one to use as a chip donor. 

[+-^CrossBow^-]

I should also mention that the way the audio is handled on this mod will cause you issues in the future. For starters on your picture of what you have done, I don't see any wire to handle the external audio line in off the cartridge port? So Pokey games won't have any audio and that will be noticed with flash carts as well. The only audio pickup I do see is directly off the TIA audio output and there isn't any resistors or anything to drop the audio level down to a more proper level. So even if you do add in the pokey external audio, you are still going to have balance issues with the TIA always overpowering the pokey audio and making it difficult to hear or hear at all with games that use both TIA and pokey like Commando.

 

In the future, as you have the equipment, just remove the RF modulator completely if you don't want it there. But also know there are other AV upgrade options that don't require having to remove anything off the system to use them that will produce as good and likely even better results.

 

 

[Officepot]

29 minutes ago, -^CrossBow^- said:

I should also mention that the way the audio is handled on this mod will cause you issues in the future. For starters on your picture of what you have done, I don't see any wire to handle the external audio line in off the cartridge port? So Pokey games won't have any audio and that will be noticed with flash carts as well. The only audio pickup I do see is directly off the TIA audio output and there isn't any resistors or anything to drop the audio level down to a more proper level. So even if you do add in the pokey external audio, you are still going to have balance issues with the TIA always overpowering the pokey audio and making it difficult to hear or hear at all with games that use both TIA and pokey like Commando.

 

In the future, as you have the equipment, just remove the RF modulator completely if you don't want it there. But also know there are other AV upgrade options that don't require having to remove anything off the system to use them that will produce as good and likely even better results.

 

 

 

1 hour ago, DrVenkman said:

The only source for new old-stock is Best Electronics and they can be … difficult to deal with (search the Forum for details). New NTSC TIA chips are also now about $50, which seems insane to me but it is what it is. Other than taking a crapshoot on eBay or AliExpress, your best bet might be looking for cheap, working 2600 and salvage the chip from that one. All Sixer models and many 4-switch woody models are socketed, which might make chip removal a little easier if you find one to use as a chip donor. 

Thank you both for all the great info, I have a few 2600s that do not work. I will take a chip off one of those and see how it does, thanks again! In the future I will look at better AV mods!

[Bratwurst]

That AV mod guide on vintagegamingandmore is offensive. Please stop drilling holes in console shells. Desolder the RF modulator completely and pop in one of these if you have access to a 3D printer, or I can print you one myself:

 

https://www.thingiverse.com/thing:4235463

 

 

[+DrVenkman]

5 minutes ago, Bratwurst said:

That AV mod guide on vintagegamingandmore is offensive. Please stop drilling holes in console shells. Desolder the RF modulator completely and pop in one of these if you have access to a 3D printer, or I can print you one myself:

 

https://www.thingiverse.com/thing:4235463

 

 

Eh, no thanks. No room for S-video and most of us don’t have a 3D printer, nor do we want to pay for a print. A neatly drilled set of holes for composite/audio and potentially S-video is fine provided it’s done carefully. Some masking tape, a pilot hole and a step-bit and you’re golden. Easy peasy. 

[+-^CrossBow^-]

8 minutes ago, Bratwurst said:

That AV mod guide on vintagegamingandmore is offensive. Please stop drilling holes in console shells. Desolder the RF modulator completely and pop in one of these if you have access to a 3D printer, or I can print you one myself:

 

https://www.thingiverse.com/thing:4235463

 

 

That is an awesome thing but sadly the options are limited if you wanted composite and s-video using standard jacks in the process or keep functioning RF out. Then you have to do something like this...

 

 

[alex_79]

If the shell is in good condition without cracks, I still prefer to keep it original and a simple solution is to route very short cables terminated with inline connectors (rca, mini-din, scart, hdmi, or whatever you need) out of existing holes. That way the console can always be restored in its original state in the future.

 

 

 

 

 

[Officepot]

UPDATE!

 

I replaced the TIA chip with one I had from a 2600. But the issue persists in almost the same state. I can get about one second to two seconds into a 7600 game with good sound and picture. Then the console freezes, sometimes it will sputter and unfreeze and then refreeze again for a bit before finally freezing and not coming out of it. 2600 games still just give randomly colored lines and show no other signs of life. Here is what the board looks like now with the new chip. I wonder if this is a power issue? Since it seems to be struggling on and off? I did recap the console and if I test the power supply unloaded I get 14.44V. Any guidance on what to try next would be great!

[+DrVenkman]

That’s too bad. Also, you probably should have installed a socket in that 7800 when you swapped the TIA, just in case. 

 

Without access to some diagnostic tools, it’s hard to tell you where to go next. At the very least, you need a copy of the schematics and a multi-meter. A ‘scope would be better but not necessary if you know what to look for with the meter. 

 

It honestly might end up being cheaper and less trouble to find a new working unit instead of throwing money and time into trying to diagnose this one. 

[Officepot]

Just now, DrVenkman said:

That’s too bad. Also, you probably should have installed a socket in that 7800 when you swapped the TIA, just in case. 

 

Without access to some diagnostic tools, it’s hard to tell you where to go next. At the very least, you need a copy of the schematics and a multi-meter. A ‘scope would be better but not necessary if you know what to look for with the meter. 

 

It honestly might end up being cheaper and less trouble to find a new working unit instead of throwing money and time into trying to diagnose this one. 

You're probably right, I will try a few more things before I give up on this one and if I make any headway will post it here. I should have taken the socket off the 2600 but regardless it is what it is. I will check voltages with the schematic and see if anything looks out of the ordinary (see if it does happen to be an odd power issue). Thanks again!

[Officepot]

On 7/28/2023 at 3:14 PM, Officepot said:

You're probably right, I will try a few more things before I give up on this one and if I make any headway will post it here. I should have taken the socket off the 2600 but regardless it is what it is. I will check voltages with the schematic and see if anything looks out of the ordinary (see if it does happen to be an odd power issue). Thanks again!

Wanted to post a final update to this. I ended up using this board as a donor board. (Needed the cartridge connector for a working board with some broken pins). Other board works great now! One more saved from the dump! Thanks for everyone's help.