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bfollowell

My new Atari 400 needs some TLC!

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I was gifted an old, 1979 Atari 400. It definitely needs a lot of work and TLC. She's pretty dirty and needs a good bath. One of the bottome case screws is missing and there were only two internal screws in place. There's some bodge wire going from the power board up through the interlock switch plunger hole in the aluminum shield preventing me from removing the shield, so I'll have to remove it first. The internal speaker is missing and one of the screw mounts inside is broken. More of the keyboard doesn't work than does. I had to fix down the interlock switch as there is no plunger any longer. It has some sort of composite video/audio mod terminating in RCA jacks mounted and soldered to the power board going through a hacked out square hole in the back where the old channel selector switch used to be. They're pretty loose and will probably go eventually in favor of one of TF_HH's Super Color CPU cards.

 

As you can see, I have my work cut out for me this winter, but it should be fun and rewarding. I never really thought I wanted a 400, but once this one just sort of fell into my lap, I've gotten really excited about it.

 

I was hoping to peek & poke around in Basic and find out what version of OS it has and whether it has a CTIA or a GTIA but with most of the keyboard not working, that's really not an option just yet. I guess I can check out the graphics chip visually, once I get the shield off.

 

The keys that are working on the keyboard are:

Spacebar, X through M ,./
Left & Right Shift, Ctrl
S through L ; +

 

Everything else appears completely dead. Is there a keyboard matrix legend available anywhere or is it the same as the XL machines? I haven't had any luck finding one so far. I'm assuming the 400 uses 4051s to control keyboard input as well, so I'll need to check those out as well. It could be that the keyboard itself is just fine.

 

Anyway, wish me luck with my new project and I welcome any advice and suggestions. I've never had any experience with the 400, and my last experience with any 400/800 was my original 800 that died in 1986.

 

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Edited by bfollowell
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nice acquisition! the 400s have a proper '70s look 😎

you can do an s-video and audio mod quite easily - they can both be tapped directly from points on the PCB. however the TF_HH card is superior and his 48k card is great too. if you have access to a 3d printer it would help tidy up that cable exit hole.

this is all i have for keyboard matrix reference:

 

Standard_400_Keyboard1.jpg

Edited by xrbrevin

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56 minutes ago, flashjazzcat said:

My God. Do people who mod cases not own drills and files?

 

I thought the same exact thing. I'm certain the case is brittle, so I don't want to do much, but I may break out the Dremel and the files and see if I can at least level out the hole and smooth it a little bit.

 

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1 hour ago, flashjazzcat said:

My God. Do people who mod cases not own drills and files?

mustve been drinking balmy-fluid at the time!

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sounds like you have one or two bad CD4051s.  Not that the keyboards can't get damaged.... but with that number of keys out, it sounds more likely to be one or both CD4051s.

 

As for the missing plastic piece to operate the cartridge port power interlock, I may have one available.  Though you could just solder a bridge wire on the interlock switch terminals on the power supply board.  You wouldn't have the interlock 'protection' though.

 

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6 minutes ago, cwilbar said:

sounds like you have one or two bad CD4051s.  Not that the keyboards can't get damaged.... but with that number of keys out, it sounds more likely to be one or both CD4051s.

 

As for the missing plastic piece to operate the cartridge port power interlock, I may have one available.  Though you could just solder a bridge wire on the interlock switch terminals on the power supply board.  You wouldn't have the interlock 'protection' though.

 

 

Yeah, I'm not necessarily worried about having the "protection" of the interlock, but more concerned about having a unit that's as complete as I can get it. Even when I get a plunger, I'll probably still defeat the switch so I can open the door without the 400 powering down. I just want the unit complete. I'm planning to order an interlock plunger from Brad at Best tomorrow, as well as a replacement speaker and a couple of other odds & ends. I had a 600XL that came in last fall with a partially working keyboard and it wound up having a bad CD4051, so that was an initial thought on this one as well. Thanks for your help in my keyboard matrix primer thread. Now that I'm certain how those work, it'll be fairly easy to pull the old Fluke out when I get up tomorrow afternoon and check out those troublesome keys. At least it should help me narrow it down to keyboard or not.

 

I've downloaded some good manuals for the 400 and one, a Sears 400 repair manual of all things, listed the 3 screw sizes used, so I'll pick those up at Home Depot this weekend. Then I'll need to see if I can figure out a good way to repair that broken screw mount. Once I get that repaired and a full set of screws in it, that should help tighten things up considerably.

 

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25 minutes ago, bfollowell said:

Then I'll need to see if I can figure out a good way to repair that broken screw mount.

I've had good luck with both Plastruct Plastic Weld as well as JB Weld PlasticWeld before.  Haven't tried either one on a 400, though, so no idea how compatible it might be with its plastics.  Start small and use as little as possible :D

 

If you should decide to go with a heat-based plastic welding kit, please let us know what does or does not work for you.  It's something I've been thinking of picking up for a while, and could use some real-world testing of it in the sorts of situations I'd be likely to use it for.

 

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Well, I don't have the keyboard fixed yet, but the troubleshooting is done. I checked at the motherboard connector side of the keyboard ribbon cable and nothing connected to lines 1-5 worked consistently, if at all. I went back to the solder joints on the keyboard PCB side of the ribbon cable and every key press checks out perfectly, so it looks like a bad ribbon cable. I ordered a NOS 400 keyboard from Best today, and I'll use it to checkout the computer further, but more than likely, I'll clean this keyboard up really well and come up with a new ribbon cable and connect setup and get this keyboard going again and use it. Then I'll set the NOS keyboard back as a spare. Or I may use it. It may be kind of hard to not use a pristine, perfect looking keyboard when I know I have it. Either way, I'll still repair this original keyboard.

 

 

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I don't have my new 400 keyboard yet, or the old one repaired yet, so there isn't much I can do with the Atari itself, but I checked out the CPU and motherboard cards. It looks like I definitely have a CTIA and that memory card doesn't look original to me though, admittedly, I don't really have a lot of 400 experience to base that on. There are 16 16Kx1 chips on there, so is that a 16KB card? Does that look like an original card to you guys? My new keyboard should be in Tuesday, and I'll dig a little further then, to see what version of OS it has.

 

IMG-5618.thumb.JPG.3309a799943c95001f3bb6f65bb7f0eb.JPGIMG-5619.thumb.JPG.0c0572fa70440b0df55ac9aeadcd05cd.JPG

Edited by bfollowell

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OK, it's been far too long since my computer electronics courses in college. The part datasheet says 16Kx1, and there are 16 chips, so how do you get 32K? I'm not doubting you, mind you, just trying to get the old brain going again and understand. I do see the MM1632 model number though, now, so again, I don't doubt you. The math just doesn't work in my head.

 

As far as I remember, Atari came out with a 48K upgrade for the 400, but I'm not aware of them coming out with a 32K upgrade, so that definitely marks it as an aftermarket board, correct? I guess the Intec Peripherals Corp stamp sort of marks it as non-Atari as well.

 

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1 hour ago, bfollowell said:

OK, it's been far too long since my computer electronics courses in college. The part datasheet says 16Kx1, and there are 16 chips, so how do you get 32K? I'm not doubting you, mind you, just trying to get the old brain going again and understand. I do see the MM1632 model number though, now, so again, I don't doubt you. The math just doesn't work in my head.

 

 

I think I may have figured it out. OK, it's an 8-bit system/data bus, so 8 16Kx1 chips would be 16K, so 16 of them would be 32K. Does that sound right?

 

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35 minutes ago, xrbrevin said:

yes indeed 🤓

 

Man! It's been way too long! That, and I've spent the past twenty-five years flying a desk, pushing paper, and taking care of crying, glorified primadonnas, rather than getting to do any real work. It's good to get the old brain cells moving again.

 

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That 1979 400 had some service. Many CPU board chips are dated 1980, the latest, 8041, 41st week. Also, of course, the 32K Intec board, with chips from 1982.

 

What datecodes do you see on the motherboard?

Edited by ClausB

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20 minutes ago, ClausB said:

That 1979 400 had some service. Many CPU board chips are dated 1980, the latest, 8041, 41st week. Also, of course, the 32K Intec board, with chips from 1982.

 

What datecodes do you see on the motherboard?

 

I have no idea what the date codes may be, or how to interpret them, but here's an image of the top side of the motherboard.

 

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On 10/28/2021 at 9:24 PM, flashjazzcat said:

My God. Do people who mod cases not own drills and files?

Probably, they just don't take them out of the display cases..

 

Mind you, saying that, I was willed a load of gear including tools by me old mate Bob, it amazes me just how much of a mess I can do with a genuine Dremel, nice files  and multiple drills. It's more like a murder scene than a mod..Thankfully, I don't mod things very often...(twice, I think)

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4 hours ago, bfollowell said:

here's an image of the top side of the motherboard.

A couple of the ROMs are from 1980 but all the other chips are from 79 or earlier. It was common for early OS ROMs to be replaced when the machine went in for service.

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35 minutes ago, ClausB said:

A couple of the ROMs are from 1980 but all the other chips are from 79 or earlier. It was common for early OS ROMs to be replaced when the machine went in for service.

It'll probably be the more common Rev.B, though I believe that came out in fall 1981. I was really hoping for something a little older, maybe Rev.A, or maybe even the almost unheard of and rarely seen Operating System 255.

 

It's a shame that I didn't get the original chips and memory card for those that had been upgraded, though, it was a gift, and I got the feeling that the guy who gifted it to me probably wasn't the original owner or anything. At some point, after installing the AV mod, the RF modulator was removed, not that I'd have ever used it, but that's just one more thing to make it a little less original.

 

It looks like my NOS keyboard should be in tomorrow or Tuesday. I'll do a little peeking when it gets here and confirm the OS revision.

 

Edited by bfollowell

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My Best order came in today. NOS keyboard, console speaker, and interlock switch plunger. She's a little closer to an original machine now. I confirmed every key press is picked up, so it was definitely the ribbon cable, and only the ribbon cable before. This also let me poke around a little, or peek, as the case may be. As expected, this is a Rev.A/NTSC machine and it has 29,710KB free, so as everyone expected, this is a 32K machine. It's had some changes over the years, but it will still be a nice little machine when I get it all cleaned up and back together.

 

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