Atari Power Supply and Snow

[christo930]

I just got a Harmony cart and I was having some problems with it. Well, one of the things I did was put a meter on the power supply, but it seems a bit high to me at 14.5 volts, but I do know they tend to run high.  Outside of the Harmony carts I haven't had any other problems, except a lot of snow on 2 different Sixers.  What causes the snow?  Is this just a dirty contact on the internal channel selector switch?  My 7800 and Jr both have very good screen quality.  The TV I have it hooked to is a mid 90s RCA with a pretty good electronic tuner and there are no problems with the 7800 or the junior (outside of problems with the Harmony cart).  IIRC, one of the reasons I use the Jr is this very thing (snow), but I don't remember being as bad as it is. They have been in a dusty storage environment for 15-20 years.

[+Stephen Moss]

If the 14.5v is off load (2600 off) then that is OK, if it is the on load I would be more concerned.

Snow is just the product on electrical noise in the signal. You might have a bad ground connection either in the cable or to the output connector on the 2600. Presumably you are using the same cable and TV with the 7800's, in which case if there is no snow with them the fault is with the 2600's.

Check the ground first, if that seems to be OK then you have to consider other things such as low output level, or if you are tuned into a particular channel on the TV just that the modulation frequency for the 2600's may be a little off that of the 7800's it may just be that the TV just not quite tuned in to them.   

Edited May 29, 2020 by Stephen Moss
Added additional possibilities

[christo930]

5 hours ago, Stephen Moss said:

If the 14.5v is off load (2600 off) then that is OK, if it is the on load I would be more concerned.

Snow is just the product on electrical noise in the signal. You might have a bad ground connection either in the cable or to the output connector on the 2600. Presumably you are using the same cable and TV with the 7800's, in which case if there is no snow with them the fault is with the 2600's.

Check the ground first, if that seems to be OK then you have to consider other things such as low output level, or if you are tuned into a particular channel on the TV just that the modulation frequency for the 2600's may be a little off that of the 7800's it may just be that the TV just not quite tuned in to them.   

It's the open circuit voltage. The 7800 and Jr have an RF jack whereas the other models have an internally attached RF lead.

I know the JR puts out a higher signal than all of the earlier Atari models.  The only thing I can really think of is a dirty channel switch.  The adapter (IIRC, I think it's called an F adapter) on the back of the TV is clean and the wires coming out of the Ataris are clean. They are the original Atari supplied cables (including the other one for the Jr and the 7800) so unless they are damaged in some way, they would have the proper shielding.

[Voxel]

14 hours ago, christo930 said:

What causes the snow?

1) A reduction in signal quality from interference.

2) A reduction in signal strength from increased resistance.

 

You can remove and check the RF lead for continuity for the core and shielding separately (end to end) as you flex the cable (be mindful of any kinks smaller than 1inch in radius as it could indicate an area of stress and weakness in continuity.

 

Equally important is to check the lead for a short/leak by doing a continuity check with the "core to the shielding" once removed.  If it's good then you'll be checking the components on board.

 

If your checks take you to the components on the board, check the tuning pots, by adjusting them for best signal, in case of drift.  Then give the components a good visual for overheating or dry solder joints and good connections.  Lastly if no suspect components are identified your electrolytic capacitors will be due a replacement.

 

[christo930]

I cleaned all 7 switches on 2 of the Ataris and it completely cured the snow problem.  But one of them won't run certain games on the Harmony cartridge but runs others with no problem.  I haven't completely dismantled the Ataris, both of which are heavy 6ers (a Tele-games and an Atari) with a giant hunk of aluminum over the motherboard.  There are 3 electrolytics on the board that has the switches, 2 of which appear to be for the power. One large 2200 uf, a smaller one near the voltage regulator and then on the other side there is a 3rd one near (but not in) the RF box.  There is a sub board the ports are connected to that is loaded with noise suppression ceramic caps for the JS ports.

 

Are there any caps on the main circuit board that are known to fail?  The main board is separate from the heat generating voltage regulator.  Also, I am having these problems on multiple machines. I have a Jr that won't run certain games and now one of these heavy 6ers that won't some of the games. I've also tried multiple power supplies.

[+-^CrossBow^-]

Some H6 units have issues with some of the earlier homebrew games. I know that Stay Frosty 2 didn't work on one of my H6 units until I did the small trace cut mod to fix it. Can't recall exactly what trace it was but it was easy enough and easily reversed if needed. The forums make mention of it. 

 

Which games did you have issues with on your Harmony?

[+DrVenkman]

19 hours ago, christo930 said:

Outside of the Harmony carts I haven't had any other problems, except a lot of snow on 2 different Sixers. 

Not sure what you mean by that. Do you mean the same Harmony Cart causes now on two different Sixers? Or that your Sixers have snow with the power supply you're using? 

Have you measured the voltage inside the board at the voltage regulator input and output legs? Is the PSU you're using original or some modern replacement? If you're getting that voltage off a modern switching supply, that's probably not a good thing. Older, unregulated supplies tend to be several volts high when measured with no load (e.g., the system not running a game). 

[christo930]

4 hours ago, DrVenkman said:

Not sure what you mean by that. Do you mean the same Harmony Cart causes now on two different Sixers? Or that your Sixers have snow with the power supply you're using? 

Have you measured the voltage inside the board at the voltage regulator input and output legs? Is the PSU you're using original or some modern replacement? If you're getting that voltage off a modern switching supply, that's probably not a good thing. Older, unregulated supplies tend to be several volts high when measured with no load (e.g., the system not running a game). 

I've solved the snow problem by cleaning the switches with contact cleaner/lube.  I cleaned all 7 of them (rf + 6 regular switches) on both of the heavy 6ers and solved the snow problem (the snow prob was completely separate from the harmony cart problems).  However, one of the heavy 6ers and a junior are having difficulty running certain games on the harmony cart.  Oddly enough, on the junior it is not displaying the hourglass for any game, even ones that work.  Games that don't work are space rocks, frantic, DKarcade, while others work just fine.   The junior will play other dpc+ games, just not space rocks, frantic and another one whose name escapes me at the moment.  But they all worked fine on the 7800.

I've tried multiple power supplies.  The 14.5v was open circuit not even plugged into the atari, just with the meter leads across the connector. 

I would assume that the regulators are working OK because all of the other games work fine.  I am not aware of any diagnostic carts that actually run tests on the hardware. But if you know of any, I'd appreciate any assistance you can provide.   Tomorrow I can check the output of the regulator, but I suspect that is going to be fine.

[christo930]

6 hours ago, -^CrossBow^- said:

Some H6 units have issues with some of the earlier homebrew games. I know that Stay Frosty 2 didn't work on one of my H6 units until I did the small trace cut mod to fix it. Can't recall exactly what trace it was but it was easy enough and easily reversed if needed. The forums make mention of it. 

 

Which games did you have issues with on your Harmony?

Frantic, space rocks and one other one that slips my mind at the moment.  Funny thing is, other dpc+ games worked. This is on multiple 2600s.  But all the games load and run fine on a 7800.

[+-^CrossBow^-]

Space Rocks might have been another that had issues with some H6 units. Again, if you search the forums a bit you will see where there is mention to cut a trace on the earlier boards that solves the issue. It was several years ago when I did it on my H6 so I don't recall exactly what the mod was right off hand.

 

[+DrVenkman]

I just pulled my completely-stock Tele-Games Heavy Sixer off the shelf and tested both Space Rocks and my Harmony Cart with it. Both work great. Man, I forgot how amazing a Heavy Sixer looks through RF on a CRT. Before Atari started cost-reducing and simplifying, that system produced a fantastic picture. If only all retro-systems looked that good through RF (7800, I'm lookin' at you, bub ...)

 

 

[christo930]

Now the 7800 won't play some of the commercial games.  I think it's possible the cartridge is flakey. 

[Voxel]

18 hours ago, christo930 said:

I think it's possible the cartridge is flakey.

It's sounding like the weak link.

[christo930]

4 hours ago, Voxel said:

It's sounding like the weak link.

Is there any way to test this thing, like a diagnostic tool?  I wish there was one for the atari. 

 

I am consistently running into ROMs that work OK on one system and not the other.  The Burgertime ROM won't run on the 7800, but will run on the Heavy sixer and Frantic won't run on the heavy sixer but will run on the 7800.  Now, most of these newer ROMs I don't have the cartridge, but with Burgertime I do and so I am going to see if it will run on the 7800 and also running on a cuttle cart, which I am almost certain that it does.

[+DrVenkman]

11 hours ago, christo930 said:

Is there any way to test this thing, like a diagnostic tool?  I wish there was one for the atari. 

 

I am consistently running into ROMs that work OK on one system and not the other.

Test what “thing”? Your 2600 or your 7800?  There are a number of diagnostic cart roms out there (check ROM Hunter’s Collection on AtariMania for a one-stop shop of stuff). Most of the diagnostic carts want you to have a test plugs to insert into the joystick ports but some of the tests don’t require them.

 

As for 7800 compatibility, that’s more likely an issue with your Cuttle Cart, not the ROM. I have yet to run across a 2600 ROM that flat doesn’t work on my 7800, but I use a Harmony Cart not a Cuttle Cart. 

[christo930]

45 minutes ago, DrVenkman said:

Test what “thing”? Your 2600 or your 7800?  There are a number of diagnostic cart roms out there (check ROM Hunter’s Collection on AtariMania for a one-stop shop of stuff). Most of the diagnostic carts want you to have a test plugs to insert into the joystick ports but some of the tests don’t require them.

 

As for 7800 compatibility, that’s more likely an issue with your Cuttle Cart, not the ROM. I have yet to run across a 2600 ROM that flat doesn’t work on my 7800, but I use a Harmony Cart not a Cuttle Cart. 

Sorry I wasn't more clear.  Is there a way to test the Harmony Encore cart?

The Burgertime ROM works with the 7800 on a cuttle cart, but not the Harmony cart. A bunch of ROMs that work on the 7800 using the Harmony Encore cart won't work on a Jr I have.  Frantic will work on the 7800, but not the Junior.  When in the junior, the yin/yang hourglass graphic never appears even when it loads carts that work.  I have not come across any rom yet that will not work in any of the Atari consoles I have and none of the 2600s will load every game I have tried. So far, I have tried 2 heavy sixers, a junior and a 7800. 

None of the diagnostic carts I have on the SD card have tests for the internal chips.

[Voxel]

19 hours ago, christo930 said:

Is there any way to test this thing

It appears intermittent so I'd check the contacts (solder pads) are in contact with the cartridge sockets.  The Harmony cart may be sound but the cartridge slot on the consoles may be fine mating with other cartridges but just not this one. 

 

It could also be that certain versions of the ROMS do not work well, it sounds like a lot of work trying different versions of the same game, but that has happened to me (though I'm assuming you may have already a good list of working ROMs).

 

I no longer have a 7800.  However for 7800 Diagnostics I can point you here:

http://pages.cs.wisc.edu/~harvey/7800/diag.html

(You have a bit of a read and need to scroll down before you get the diagnostics ROM)

 

Lastly (if all else fails read the manual) maybe I should have put checking the manual first, it points you to the dedicated forum for any issues, someone may already have dealt with this issue (after reading a few posts it sounds like a lot of trawling).

 

[christo930]

On 6/1/2020 at 4:58 PM, Voxel said:

It appears intermittent so I'd check the contacts (solder pads) are in contact with the cartridge sockets.  The Harmony cart may be sound but the cartridge slot on the consoles may be fine mating with other cartridges but just not this one. 

 

It could also be that certain versions of the ROMS do not work well, it sounds like a lot of work trying different versions of the same game, but that has happened to me (though I'm assuming you may have already a good list of working ROMs).

 

I no longer have a 7800.  However for 7800 Diagnostics I can point you here:

http://pages.cs.wisc.edu/~harvey/7800/diag.html

(You have a bit of a read and need to scroll down before you get the diagnostics ROM)

 

Lastly (if all else fails read the manual) maybe I should have put checking the manual first, it points you to the dedicated forum for any issues, someone may already have dealt with this issue (after reading a few posts it sounds like a lot of trawling).

 

The ROMs I have work on the Harmony cart, just not all in the same machine. Rom X works on this 2600, but that 2600 and vice versa.

 

I don't have a manual.  I paid for the cart only.

[Voxel]

1 hour ago, christo930 said:

Rom X works on this 2600, but that 2600 and vice versa.

I'm quite fortunate if a game does not work on one of my machines, it fails on the rest too  (or maybe I'm reading that wrong and I'm not so blessed).

 

As alluded to before if a game works intermittently I'm suspecting it's the cartridge connector (Harmony) not mating and the socket on the machine (maybe the gap needs closing).  You could hold it (VCS) upside down and brush it (cartridge slot) out in case there if dust causing a bad contact.  Different games may use different pins for banking etc, so may not be consistently working on all the machines if contacts are bad.

 

I'll put this last it's a bit far fetched but I'll say it anyway.  Open up the units and confirm the board revisions and ICs are the same.  It may be a deeper revision issue if all the units are sound component wise.  It's a real unlikely event finding you own a bunch of obscure revisions (i.e. a single chip 2600 Jr)

 

The manual is online:

https://harmony.atariage.com/files/harmony_manual_v2_online.pdf

 

The manual refers you to check for a similar issue or post a new one here:

https://atariage.com/forums/forum/124-harmony-cartridge/

 

As mentioned I took a peek and you've got a lot of trawling...

[christo930]

On 6/8/2020 at 4:29 PM, Voxel said:

I'm quite fortunate if a game does not work on one of my machines, it fails on the rest too  (or maybe I'm reading that wrong and I'm not so blessed).

 

As alluded to before if a game works intermittently I'm suspecting it's the cartridge connector (Harmony) not mating and the socket on the machine (maybe the gap needs closing).  You could hold it (VCS) upside down and brush it (cartridge slot) out in case there if dust causing a bad contact.  Different games may use different pins for banking etc, so may not be consistently working on all the machines if contacts are bad.

 

I'll put this last it's a bit far fetched but I'll say it anyway.  Open up the units and confirm the board revisions and ICs are the same.  It may be a deeper revision issue if all the units are sound component wise.  It's a real unlikely event finding you own a bunch of obscure revisions (i.e. a single chip 2600 Jr)

 

The manual is online:

https://harmony.atariage.com/files/harmony_manual_v2_online.pdf

 

The manual refers you to check for a similar issue or post a new one here:

https://atariage.com/forums/forum/124-harmony-cartridge/

 

As mentioned I took a peek and you've got a lot of trawling...

They are sending me another one.  I really don't think the problem is my Atari machines.  So I guess I'll see when the new one arrives.  Hopefully this will solve the problem for me.

[Voxel]

21 hours ago, christo930 said:

Hopefully this will solve the problem for me.

Good luck!