[Capacitor c55 issue]

18 hours ago, DrVenkman said:

You haven't been using AC with your 7800 have you?!? That would be bad. 

? Thankfully, no.  DC for both.  The little I know about electronics encompasses that at least ?

[Capacitor c55 issue]

2 minutes ago, DrVenkman said:

There's no rectifier in the 7800 - it doesn't need one, since the power supply provides DC current already. The only way it would need a rectifier would be if it used an AC power supply.  

PAL machines have ASTEROIDS built in. NTSC machines do not unless modified. 

Well, that makes sense.  My MC-10 is an AC powered machine. It mostly works fine, though, with a DC power supply (It just needs minus voltage to operate the serial port).  I've been testing both with the same wall wart and got confused. ?

[Capacitor c55 issue]

2 hours ago, DrVenkman said:

That’s not a rectifier - the 7800 already receives DC current input and has no need for one. It’s a PNP transistor. The pinout is Emitter - Collector - Base. The voltage readings will depend on what is being input to it. You’ll need to refer to the schematic to figure out what those should be.

 

That said, it’s part of the power supply circuit - since your console doesn’t have an issue powering on, that’s almost certainly not a problem. You need to focus your troubleshooting on the components involved in 7800 games - the physical condition of the cartridge slot pins (especially the set of four on either end which are 7800-specific) and continuity from there to the rest of the system; MARIA and the BIOS and SRAM chips. All those are 7800-specific. 

And after I read your whole message, ? I'll post some pictures of the pins and test continuity from there to the rest of the system.  I cleaned them and they appeared to be in good condition on an earlier inspection, but I'll give them another go over.

[Capacitor c55 issue]

2 hours ago, DrVenkman said:

That’s not a rectifier - the 7800 already receives DC current input and has no need for one. It’s a PNP transistor. The pinout is Emitter - Collector - Base. The voltage readings will depend on what is being input to it. You’ll need to refer to the schematic to figure out what those should be.

 

That said, it’s part of the power supply circuit - since your console doesn’t have an issue powering on, that’s almost certainly not a problem. You need to focus your troubleshooting on the components involved in 7800 games - the physical condition of the cartridge slot pins (especially the set of four on either end which are 7800-specific) and continuity from there to the rest of the system; MARIA and the BIOS and SRAM chips. All those are 7800-specific. 

Well, I never claimed to be an electronics expert, thankfully! ? I was troubleshooting an issue with my MC-10 earlier this week involving its rectifier, and the rectifier was a three-pronged item that, to my ignorant eye, looked like the part on the 7800 I tested. ? Now I have to go find the rectifier!

[Capacitor c55 issue]

Ok, got some time to test voltages.  The reading across the big cap seems to be stable at ~8.95v under load with a 2600 cart inserted.  I got strange readings from the outer pins of the rectifier, though.  Mostly under 1v on both sides.  If the rectifier is working properly, what should the values be?

[7800 Serial Number List]

Here is my serial number from an A1 with expansion port:

 

[Capacitor c55 issue]

5 hours ago, Stephen Moss said:

Thanks for the clarification, I probably could have been a little clearer in my post.

 

What I was trying to say although probably in an over generalised way was that (again I may be wrong but) I believe that the TIA is responsible for generating the video for 2600 games and MARIA for doing the same for 7800 games.

If that is the case then as the system reportedly plays 2600 games without issue it is probably safe to assume that elements common to both, i.e. Power On/Off latch, power supply, clock, 6502, 6532 and RF modulator are all OK. Therefore it would be logical to conclude that the problem is likely to lie with either MARIA, 7800 cart detection/7800 only cart connections or the logic that determines whether MARIA or TIA is responsible for video generation (maybe BIOS and U11/U12?).

In which case as the video output of both appear to be ORed together by U3 I would speculate that the video output for the TIA would be logic 0 if MARIA alone is generating the video and vice verser, therefore if there is no video output for 7800 games either something is stopping MARIA from outputting video signals or stopping them from reaching U3 thus causing the blank screen.  

 

If there is a short on the power supply a muilti-meter is all you need. Try measuring the input voltage across the big 2200uF cap (C62?) and between the middle pin and the two outer pins of the 7805 voltage regulator, when...

a) The power is off

b The power in on 2600 game inserted and 

c) The Power on 7800 game inserted.

 

Also thinking about what I said above try measuring the voltage on pins 1 & 2, 4 & 5, 9 & 10 and 11 & 12 of U3 with a 7800 game inserted and a 2600 game inserted, values will either be 5V, 0V or an indeterminate intervening voltage as they change state between 5V and 0V for the video signals.

 

If you have any 7800 games that are known to auto run an attract screen with sound once powered up try one of those to see if the audio is also affected or if it is just video.

 

You could always build a logic probe if you really want one there, are various schematics on line.    

Thanks for the detail!  I'll try to get some voltage measurements and update here.  And I ordered a logic probe, so I should be able to do a little more in-depth debugging this weekend.

[Capacitor c55 issue]

@-^CrossBow^- I did take a card with some ipa-wet paper and put it into the slot and used Q-tips to clean the visible parts of the pins.  Not much room to get deep into the extra 7800 pin at the edges, so it might still be a corrosion issue, I suppose.  Although I tried a few cartridges last night and when I put a 7800 cart in, it would stop powering on at all (even after going back to a known working 2600 cart), which means something is shorting out, doesn't it?  I tried again this morning to similar results, so maybe reconnecting that cap is causing the short.  Wish I had an oscilloscope, or even a logic probe, I suppose.  All I have is a multimeter for testing.

[Capacitor c55 issue]

8 hours ago, -^CrossBow^- said:

You already stated earlier that you are able to play 2600 games so the issue isn't the system not power up. I assume you are just getting a black screen when trying to play 7800 games? Do you even see the atari rainbow loader when trying to start up with a 7800 game?

 

BTW...where are you located roughly?

 

I was able to get one 7800 game to play long enough for a short game, and I think I got another to display the rainbow loader, but then it went to black screen.  Everything else has been black screen.  I do have a DragonFly, although I haven't been successful in getting it to load a game, either.  I believe there are some utilities that I might be able to use, if I could get them to load.  I've just been cautious with cartridges until I know the system won't cause any damage, given I don't know what is wrong.

 

I live in the Maritimes on the east coast of Canada.

[Capacitor c55 issue]

Ok, I tested and I have continuity between that end of the capacitor and both R47 and pin 4 of the 4013.  Not sure what to try next.

[Capacitor c55 issue]

One more addition: 

On 10/4/2021 at 4:21 AM, Stephen Moss said:

-^CrossBow^- is correct that cap should be attached, the unattached end should connect to pin 4 of the 4013. So if you have trouble getting it into its original hole you could flip it over the 4013 and attach it to R47 (Brown, Black, Green, between the two caps) which also goes pin 4.  

 

When switching on the connected power unit C55 couples a transient pulse to pin 4, resetting the latch setting the Q output low, preventing Q9 and thus Q10 from conducting and the incoming power for getting to the voltage regulator setting the unit to it off state.

However, if you have a multi-meter it may be worth checking it first. Although its non attachment may have been an oversight, one reason for leaving it unattached is that it has gone short circuit. If that were the case the latch would be held in permanent reset and you could never turn the unit on.

 

The unit should still work without C55 being attached, however when the power unit is switched on without the reset pulse the Q output of the latch could randomly be high or low and so you may be plugging in the first cartridge with the unit in its on state. 

  

I think this chip has also been replaced.  Is this the 4013 chip?  The chip is labelled a TI 33A41D8 (The 8 may be a B, it's hard to tell). I can't find any info online about the chip, and I don't see any chip on the board with 4013 in the name.  I see the 4013 in the schematics, but I find it hard to map schematic details to the pcb.  Couldn't find a picture of a de-populated 7800 board online either.  That means I can't easily figure out where R47 is located on the board, either. 

[Capacitor c55 issue]

So I've reattached the leg and tested around with my multimeter before turning it on.  Everything seemed fine, but when I powered it on I got the same results.  2600 cartridges work fine, 7800 ones don't.  Examining the board some more, I think this has been recapped at some point, and one chip looks to have been replaced/resoldered.  I'm attaching picks of the parts of the board that looked worked on.  Any further troubleshooting suggestions are welcome!

 

 

[Capacitor c55 issue]

20 hours ago, -^CrossBow^- said:

My theory on this is that a power mod was attempted in the past on this console and the wrong polarity was used and blew some of the components. I'm stating that because of the solder blob on the ground trace and at the base of the FB. That is actually where I solder my wiring for power mods as well or have in the past. I used to attach pigtail cables from those points that had a standard barrel jack on them so you could use a Genesis power supply. Possible someone did something similar and the wrong PSU was plugged in. Just a guess though.

 

It's a good guess.  Someone was definitely in this machine before me and that would explain the solder work.  Unfortunately, I'm new to owning this machine, so I don't know for sure.  It was working when my sister picked it up for me, so I'm hoping the fix is relatively simple.  I also got a 5200 this weekend, complete with 4 controllers and a trackball, and was playing with that instead!  I'll try to repair the 7800 later this week.

4 hours ago, Stephen Moss said:

-^CrossBow^- is correct that cap should be attached, the unattached end should connect to pin 4 of the 4013. So if you have trouble getting it into its original hole you could flip it over the 4013 and attach it to R47 (Brown, Black, Green, between the two caps) which also goes pin 4.  

 

When switching on the connected power unit C55 couples a transient pulse to pin 4, resetting the latch setting the Q output low, preventing Q9 and thus Q10 from conducting and the incoming power for getting to the voltage regulator setting the unit to it off state.

However, if you have a multi-meter it may be worth checking it first. Although its non attachment may have been an oversight, one reason for leaving it unattached is that it has gone short circuit. If that were the case the latch would be held in permanent reset and you could never turn the unit on.

 

The unit should still work without C55 being attached, however when the power unit is switched on without the reset pulse the Q output of the latch could randomly be high or low and so you may be plugging in the first cartridge with the unit in its on state. 

  

Thanks for the details!  I'll test it out with my multimeter before I turn it on again.

[Capacitor c55 issue]

5 hours ago, -^CrossBow^- said:

Are you sure it was labeled as C55? Can you take a picture of it for us?

 

 

It's a little difficult to get a good picture, but here are a couple of angles

[Capacitor c55 issue]

Just received a 7800 that seems to play 2600 games ok, but I only got a 7800 cartridge to work well enough to play a game once.  When I examined the board, I noticed that the leg of the capacitor labeled c55 wasn't connected to the board. I'm planning on reconnecting it, but seeing as this is my first time using a 7800, I figured it's a good idea to check here first, to make sure it's not just a factory bodge.  I'm going to do a second cleaning of the connectors first, but after a post-clean test, that's the next step as far as I can see.

["Dragonfly" my version of the Atari 7800 SD cartridge]

18 hours ago, ZeroPage Homebrew said:

This sounds like what the AtariVox+ already does. As far as I know, nobody has yet to make a game that transfers information to a sequel but there's talk of it and completely possible to do with the AtariVox.

 

- James

Interesting.  I wasn't aware there was the ability to save state to the AtariVox+.  That would solve the problem, for sure.  Guess I'm buying an AtariVox+!

["Dragonfly" my version of the Atari 7800 SD cartridge]

On 9/10/2021 at 11:28 AM, -^CrossBow^- said:

Well, to be clear, it would still require you to power on the 7800 to even see anything on the screen. The way his logo graphic works now, is that if you turn on the DF cart and then power on the 7800 you see his DF logo. But once you select a rom image to be loaded, it will power off the 7800 so that the cart can load itself up to be the game/program you have selected. Then ask you to power on the 7800.

 

So if this were possible the process would look like this:

 

- Power on DF cart

- Power on 7800 - would see menu selection screen

- Use buttons on the DF to navigate the screen in the same manner you do on the LCD display

- Select the ROM you want to load and the DF then powers off the 7800 and begins to load itself up with the ROM

- DF will instruct to power on the 7800

- Power on 7800 and play the game/program you chose.

 

That seems like more steps but it just one more than what we do now really:

- Power on the DF

- use button on the DF to navigate on the LCD

- Select the ROM/Program to use and the DF will load itself up

- DF will instruct you to power on the 7800

- Power on the 7800 and play game/program you chose.

 

My concern here is that you are making the 7800 work harder here with the added switching on/off. If the DF could somehow load itself up and then issue a reset that would work similar to the Concerto does, then that would help. But this is just how I would imagine it could work assuming the DF is able to do something like this. Again, @rj1307 needs to look into this as only he would know if something like this is even possible.

 

Again, I don't see much difference in using the built in LCD vs having to do the same thing on my TV screen. In both cases, I'm using the cartridge to select what I want it to load up and simulate itself as for the game/program to use. The 7800 for all intents and purposes, doesn't know that a DF cart is even there due to how the entire thing works. It just loads up and sees what it believes is the actual game cartridge you inserted into the system. The Matoes does the same think just much more limited on storage since it used a built in flash chip for storing its rom images in this case and was limited to 144k ROM sizes in its firmware.

 

Any UI would be an imperfect solution, given what you point out.  Still, I'd be curious to see if there was a way to persist information and make it retrievable between cartridge images.  My original thought was creating a series of carts that could lock/unlock areas or provide new functionality or abilities to the user based on actions they took on another cart (kind of similar to the use of a code to transfer your character to a sequel game back in the day, just automated).  I haven't seen @rj1307 directly address this detail, so I was just wondering if it is possible.

["Dragonfly" my version of the Atari 7800 SD cartridge]

20 hours ago, -^CrossBow^- said:

I'm not sure how you would create an onscreen UI for the DF? In a nutshell what the DF is doing is loading itself up to mimic the actual cartridge you are selecting to load. That is why the cart loads up the rom data and then has you power on the console. What you are asking is for the 7800 to already be up and running and somehow select the rom from the DF, DF loads, and then the 7800 would have to be rebooted/reset in some way? But currently when the DF loads up something, it will power off the 7800 in the process and then ask you to turn it back on.

 

To me the menu navigation on the cartridge is very easy and takes me just as much or even less time than it would to select from a series of on screen options.

 

 

The UI was actually just a chance thought following from my initial thought.  The idea that made me ask the question was on the potential game/software side.  Just wondering if there was some way to push data to the DragonFly cart so it could be shared between rom images and 7800 power cycling.  I was thinking this could make for some unique mechanics, seeing as the Dragonfly stays on when the console is powered off.

["Dragonfly" my version of the Atari 7800 SD cartridge]

@rj1307 I've been studying 7800 programming and I was wondering if you've exposed any hooks so that software running on the 7800 could send commands to the Dragonfly directly, such as getting it to load a game?  Just wondering if it is possible, as that would allow someone to build an on-screen UI for the cart, or maybe a game using DragonFly-specific support. (Not sure what form that would take, just spit-balling ideas)

["Dragonfly" preorder]

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