7800 issues with Harmony and others

[KevinMos3]

One of my 7800s does not work with paddle controllers, and the other does not work with the Harmony cart. The one that does not work with the Harmony is an older model with the expansion port on board. I've read about modifying certain 7800s to make them more compatible with certain games like Robot Tank, but I don't know if that would help with the problem I'm having.

 

What might be causing it to not work with the Harmony? It will usually boot up, then start to either roll & crash or just crash. Sometimes it won't boot the Harmony at all, other times I'm able to load a game before it crashes. Would replacing capacitors help, or changing/removing certain components or resistors as with the compatibility mod?

 

Also, has anyone else heard of certain 7800s not working with paddles, and if so, is there a fix for this?

[RevEng]

If Harmony crashes but real carts don't, then my first guess would be that the power supply is marginal... try swapping the power supplies between your two 7800s and see if the problem follows.

 

There's at least one thread here that indicates that paddles not working on certain 7800s is a known issue.

[KevinMos3]

Thank you for the reply. I've already used two different power supplies... actually three, I think.

 

Might a new mosfet and caps help?.. and if so, should I go with low impedance or audio grade caps? If not, any other ideas?

 

It's too bad about the paddles with the other 7800. I wish there was a known fix.

 

edit: Just noticed that my brand-new-fresh-out-of-the-box Ballblazer (red end label) has flakiness issues, but my old Ballblazer (silver end label) works fine. I suppose this is a cart issue and not related to the Harmony problem.

Edited May 13, 2012 by KevinMos3

[+Mitch]

If you have a multi meter check the voltage regulator to see if it's putting out 5V and not a little less. The voltage regulator is just a plain old 7805.

Changing the caps doesn't hurt, just make sure the UF rating is the same. Higher voltage is fine but not necessary, the 7800 caps are only rated at 16v so you can't go much lower anyway. High temperature caps are fine but not necessary either.

The ones to change are:

C22 - 220uF 16v Electrolytic radial

C61 - 220uF 16v Electrolytic radial

C62 - 2200uF 16v Electrolytic radial

 

And if you haven't already done it, clean the cart connector on the 7800.

 

Mitch

[KevinMos3]

Okay, so going by the part number, the voltage regulator appears to be by National Semiconductor. By looking through their data sheets, the exact modern equivalent appears to be this part. It's a 1 amp... Mouser has plenty of compatible options, but would it help to go with a 1.5 amp or even a 2 amp?

[RevEng]

The schematics specify a 7805 and they max out at 1A, so don't worry about using a 2A version like 78s05. I'd measure it before replacing it, as Mitch suggested.

 

Harmony draws more current than a regular rom based cart, which is why I suspected the issue was power related... your ballblazer failure doesn't prove or disprove that theory, because I'd expect a cart with pokey audio to draw more current too.

[KevinMos3]

My initial suspicion was a power-draw issue as well... which is why I also thought testing it with the Ballblazer cart would be a good idea (and why I named the thread "and others"... but didn't mention it initially cause I hadn't tested the other Ballblazer carts yet. But later when the one Ballblazer worked and the other didn't, it kinda threw me.

 

I went ahead and swapped out the voltage regulator from another (non-working) 7800. (It was actually more convenient at the time than hunting up one of my three multimeters since my iron was hot from working on an Intellivision II). At first, the problematic 7800 seemed to work fine with the Harmony... for about 30 - 45 minutes. Then it started to roll and crashed. It seems to work fine now until it heats up (which is anywhere from 15 - 30 minutes of play). That's far better than before I swapped out the volt reg. I'm definitely ordering a new regulator and caps. They're so cheap anyway, it won't hurt to go ahead and freshen 'em up in my other 7800 as well.

 

Maybe that experience will help with putting a solid diagnosis on the problem... well, as good a diagnosis as we can get until I hunt up one of those multimeters.

[Underball]

Just a note on the paddles incompatibility that was linked to my comments here:

 

I tried everything, replaced every cap in the offending 7800, every resistor along the paddle lines to the TIA and nothing made the paddles work. But I have 2 other 7800 consoles where the same paddles work just fine. The only thing left woulf be to swap out TIA, but that's too much desoldering for me to bother with, since I have other fully functioning 7800 consoles.

[KevinMos3]

Well, parts arrived and after putting in a brand new 7805 and those 3 capacitors, I have the same results. I got a 1 A 7805 from mouser (in it now), but I also ordered a 2.2 A 7805 from another source (that only sells them in the 2.2 A flavor), which hasn't yet arrived. If it doesn't work with the 2.2 then I'm out of ideas.

 

It's a shame because this is my only 7800 (out of 4) that works with paddles, which seems kinda ridiculous. I would have thought that at some point in testing, someone at Atari would have discovered the paddle issue. Seriously, they discovered that they needed to add a resistor to make Dark Chambers work, but never realized that many units don't work with paddles? I just might send these back under warranty! That Sunnyvale address is still good right?

[RevEng]

I have a feeling your 2.2A 7805 is a normal 1A 7805... 2.2A is the peak current spec of the 7805, with 1A being the continuous spec.

 

The 78S05 is a drop-in replacement for 7805 that's rated for 2A continuous.

[+Mitch]

It's got to be some kind of timing issue then. Probably would be pretty tough to track down unfortunately.

I have a similar situation, one of my 7800s won't work with the CC2 now matter what I've tried.

 

The paddle issue is likely a bad TIA chip but the only way to test is to swap one from a known working system.

 

Mitch

[KevinMos3]

Keep in mind that when I originally swapped out the 7805 with one from another unit, it would play for at least a little while (until it heated up). Now, with the new 7805, it's the same deal. Once the unit heats up, it starts flaking out.

 

Perhaps the solution, (although not ideal), is to take the TIA from the one I'm having Harmony troubles with and see if it makes one of the other 7800s, (that work with the Harmony), work with paddles. It wouldn't hurt to socket the thing anyway. So it's the TIA and not the RIOT chip I would want to swap?

 

I could swap out the expansion port too... which is another reason I like this particular 7800, even though it serves no purpose.

[RevEng]

Keep in mind that when I originally swapped out the 7805 with one from another unit, it would play for at least a little while (until it heated up). Now, with the new 7805, it's the same deal. Once the unit heats up, it starts flaking out.

 

If it wasn't for the fact that regular games work fine, these kinds of symptoms would lead me to believe there's a cold joint or broken-but-touching lead that's getting screwed up when the unit warms up.

 

Perhaps the solution, (although not ideal), is to take the TIA from the one I'm having Harmony troubles with and see if it makes one of the other 7800s, (that work with the Harmony), work with paddles. It wouldn't hurt to socket the thing anyway. So it's the TIA and not the RIOT chip I would want to swap?

 

The paddle positions are read through TIA inputs, so it's the one to swap.

[KevinMos3]

Update: Sockets arrived, so I removed the CPU and TIA from the unit that doesn't power on & added sockets to that board. The 7800 unit that had problems with the Harmony has an expansion port and socketed CPU already. I also socketed the TIA and BIOS for future swapping/testing.

 

Well, I swapped out the CPU of the one that had Harmony issues and now it works fine, so the CPU turned out to be the problem. Also, I've found at least one other game that was having issues with that CPU: Rampage. So for some reason, after warming up, it did not work with the Harmony, some Ballblazers (but it did work fine with one of them), or Rampage. I don't know what Rampage has in common with the others. Yet it worked fine with other games I've tried so far.

 

I still need to work on the 7800s that do not work with paddles and socket those TIAs so I can swap them out and see if that causes them to be paddle compatible. I'll be out of town for a few days due to a family emergency, but will probably tackle that when I return. I'll post an update when I do the TIA swapping.

 

 

 

As for the non-working 7800, I really want to get it working again, as I believe it was my very first 7800. As I mentioned, it does not power on at all. If I remember right, it worked until a couple years ago. The power button always seemed a bit flaky, so I opened it up and noticed the power switch was soldered in crooked. This is what made the button have to be pressed a certain way to get the console to power up. Anyway, a couple years ago I soldered it in straight and ever since then, it wouldn't power up at all. I thought maybe the heat damaged the switch, so I ordered a brand new switch, but it still does not work. I've now replaced several components, touched up every last solder joint, and checked to make sure power is getting to the switch (which it seems to be), but I still get nothing. I'm going to replace a few more components, but I'm pretty much out of ideas on this one.