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leech

I may have to seek therapy for this one...

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Got my evilBay 7800 today, it came with a load of carts, so figured it was a decent deal, everything looked pretty good until I picked it out of the box and it rattled... saw the broken corner and took it apart...

This look salvageable?

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Forget the case for now - if you can clean the board (soak in deionized water in a large tub, scrub gently with a nylon brush, then rinse in isopropyl alcohol and allow to air dry ...), start looking at the components. Remove and re-seat any socketed chips, reflow any solder joints that look marginal, then power it up and see. :) 

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32 minutes ago, leech said:

Got my evilBay 7800 today, it came with a load of carts, so figured it was a decent deal, everything looked pretty good until I picked it out of the box and it rattled... saw the broken corner and took it apart...

This look salvageable?

2020-01-15 18.15.19.jpg

 

 

I've seen and worked on worse. Can you post pics of the whole pcb top and bottom?

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I would say cleaning it up and replacing that capacitor in the back (which had some weird blue goo on the bottom and looks like it has leaked) might make it work. 

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23 minutes ago, DrVenkman said:

Forget the case for now - if you can clean the board (soak in deionized water in a large tub, scrub gently with a nylon brush, then rinse in isopropyl alcohol and allow to air dry ...), start looking at the components. Remove and re-seat any socketed chips, reflow any solder joints that look marginal, then power it up and see. :) 

Ha, not a single chip on this board is socketed.  I should get some deionized water and a tub for bathing old electronics in general.... This is probably the worse looking system I've ever gotten though! 

 

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1 minute ago, leech said:

Ha, not a single chip on this board is socketed.  I should get some deionized water and a tub for bathing old electronics in general.... This is probably the worse looking system I've ever gotten though! 

 

Typical for a 7800, alas. My AT-84 machine is fully socketed (even the SRAM and logic chips), but my A1 serial number board has only the TIA socketed. 

 

Well, scrub it clean with D-I water, rinse thoroughly in iso (90% or better), then let it dry. Then and only then will you really know what you're dealing with. With a bit of luck, it's just dirt and some rust from the RF shielding. You will likely need to re-flow some solder joints but you won't know the extent of work needed until everything is clean.

 

Do you have a multimeter at least, and a good soldering iron?

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1 minute ago, DrVenkman said:

Typical for a 7800, alas. My AT-84 machine is fully socketed (even the SRAM and logic chips), but my A1 serial number board has only the TIA socketed. 

 

Well, scrub it clean with D-I water, rinse thoroughly in iso (90% or better), then let it dry. Then and only then will you really know what you're dealing with. With a bit of luck, it's just dirt and some rust from the RF shielding. You will likely need to re-flow some solder joints but you won't know the extent of work needed until everything is clean.

 

Do you have a multimeter at least, and a good soldering iron?

I do.  Though my last soldering job was me messing up one of my Lynx systems with the LCD upgrade.  Ha, but yeah I can do a reflow on it if I need to. 

I do have some 99% Isopropyl in a can that I can spray on it.  But yeah a good bath for sure.  This looks like the front end of it was stuck in a nasty river, and then someone kicked the corner.

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To be honest I think the only real issues are going to be the front panel buttons. I'd replace those out on general principle anyway and clean up that section as much as possible on the front edge. Otherwise the rest of the board looks fine.

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26 minutes ago, Bakasama said:

Uh, how much did you pay for this "fixer upper"?

125, it had a ton of 7800 games with it (and apparently one extra copy of Galaga).

4 minutes ago, -^CrossBow^- said:

To be honest I think the only real issues are going to be the front panel buttons. I'd replace those out on general principle anyway and clean up that section as much as possible on the front edge. Otherwise the rest of the board looks fine.

Yeah, kind of what I was thinking.  I mean the actual buttons still have click to them, but I'll try cleaning up the board and see if it still fires up for sure.  Who knows, my 3D printer has a large enough bed, maybe I'll just design a new 7800 case for it....

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Replace all those glass caps and all the resistors at the front and from a quick glance, I don't think anything "under the hood" looks damaged or visibly blown out. Even that huge cap at the back by the ps jack is probably still working. I'm not gonna say it's good cause I'm not sure if that is cap leak on the bottom or just build up. I'd replace it though just cause. Everything else looks ok though. Your hand is covering the voltage regulator, does it look ok? No burn by the base, emitter or collector poles?

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Not seeing any burns.  It looks much better now though after some scrubbing.

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That's a sight for sore eyes, massive improvement. I hope to see this get all fixed up!

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Yeap it did clean up nice. I still think the front panel switches will be flakey. Also amused to see a late 80s made 7800 that has the newer revision mainboard but does NOT have the extra timing circuit populated? I could only make out the date as end of Jan or early Feb 1988 from the TIA. I think Dark chambers was released later but then I've seen '87 made units that had the extra timing circuit so that is still such a mystery to me on how Atari decided when and when not to use it exactly?

 

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And the silk screen on the back says copyright 1984.  also, my partial OCD is annoyed that one of chips' label is upside down from the rest of them!

 I will hook it all up and test it when I get home from the office.   This is the first 7800 I have ever owned, I am guessing a cartridge needs to be in for any screen output to happen?

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Okay, so I had some time before leaving for the office, hooked it all up, threw my extra Galaga cart in and... got nothing.  No red light, no pew pew.

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Again...power switch. Those original switches are known to go bad over time. They are easily replaced on the cheap with near exact match. But you can also use a flat bladed screwdriver to short the switch underneath the board to trigger the power on condition. If that still doesn't work, then you start with power and start following the voltage. 

 

Common other issues are the voltage regulator and there is also a flip flop IC like what is used in the 5200 that is sadly not socketed that I've had to replace a few times on some 7800s.

 

I believe all the 7800 mainboard revisions still have a 1984 copyright on them along with the initials of one of the original board devs on the bottom side. That is why I use the chip code dates to more easily find when a specific 7800 was likely assembled. Still not a sure bet if the chips were replaced at some point, but you can usually tell as replaced chips will likely be in sockets or show a different color in their solder on the underside as opposed to the rest.

 

Also yeah...the TIA is labeled upside down because it is mounted backwards compared to the others. Look at the notch on he ends.

 

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So, last night I did the trick with a flat head screwdriver to convince it to turn on.  It gave me a white screen and occasionally one with white bars and black waviness.  But produced a beep as well.  Kind of seems like maybe a reset button was stuck or something. 

 

But yeah, definitely need to replace the switches.  Anyone know where I can order some from?

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8 minutes ago, leech said:

So, last night I did the trick with a flat head screwdriver to convince it to turn on.  It gave me a white screen and occasionally one with white bars and black waviness.  But produced a beep as well.  Kind of seems like maybe a reset button was stuck or something. 

 

But yeah, definitely need to replace the switches.  Anyone know where I can order some from?

Ask and ye shall receive!!!

 

https://console5.com/store/tactile-switch-12mm-x-4-5mm-atari-7800-power-pause-select-reset.html

 

Although I use even higher quality switches made by Alps that I order elsewhere. But these are pretty much an exact match of the OEM switches.

 

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14 minutes ago, -^CrossBow^- said:

Ask and ye shall receive!!!

 

https://console5.com/store/tactile-switch-12mm-x-4-5mm-atari-7800-power-pause-select-reset.html

 

Although I use even higher quality switches made by Alps that I order elsewhere. But these are pretty much an exact match of the OEM switches.

 

Nice!  I will order some.  I still need to work out what to do about the case.  I may end up attending to model it and 3D print me one..

Though I should do it in ABS, but I haven't had much luck with it (namely because it stinks, so I opened my window, and then it was cooling too quickly so it all cracked).

The top of the case is almost fine (one screw post is broken off, but I can glue that) the bottom part is really cracked though.

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You can also call Brad at Best electronics.  He lists both the RF shield and the case in his catalog.

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2 hours ago, joeatari1 said:

You can also call Brad at Best electronics.  He lists both the RF shield and the case in his catalog.

Cool, I'll see what he has/charges for such things.  I can probably get the rf shield to look 'okay' not that you look at it anyhow.  I kind of like the idea of designing a new case ha.  I may end up doing the composite mod upgrade at this point, if I end up scrapping the original case.

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On 1/21/2020 at 12:38 PM, joeatari1 said:

You can also call Brad at Best electronics.  He lists both the RF shield and the case in his catalog.

He said he sold out 12-14 years ago.  So... time to pull out the Caliper!

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