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Atari 130XE with 320k Upgrade Boots to Self-Test

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I recently managed to snag an Atari 8-Bit lot at an estate sale. I mostly bought it for the accessories it came with (since I already have an 800), but it also came with a 130XE. However, when I turn it on, it boots to the self-test. I pulled it apart and noticed the 320k upgrade had been done to it (according to a sharpie label on the RF shield, it was done in July, 1987). How do I interpret the memory test? Is there any set of steps I should take to try and fix this? I've attached pictures of the mod and the memory test screen (the white box one being tested in the photo passed).

 

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20191123_015325.thumb.jpg.c54b559aaf8a7194a7f1e3efb31188fd.jpg

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it either has a "reverse option basic" OS ROM or more likely the RAM is faulty. the computer will automatically start the memory test when RAM has failed.

those MT chips are notorious for being unreliable.

be careful when desoldering anything from an XE PCB as they have weak tracks

Edited by xrbrevin
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So, the first 16KB is testing OK... and the 2nd 16KB is predominabtly bad.

 

Try to boot the computer with the OPTION key held down, you should see 8 more memory test squares in the bottom row, (because it disables the 8K BASIC ROM, freeing up 8KB more RAM) but I suspect those all test green as well.

 

Usually when XE "MT" RAM chips are bad, even 1 bad chip of the 8 on the far left column on the motherboard will cause red squares across ALL rows in the self test. This leads me to suspect a problem somewhere else. Your OS ROM is probably good. The problem may be with the MMU, or some of the wires hanging off.

 

Thinking about this some more, the 2nd 16KB RAM that is showing RED is the memory region where the extended memory banks into... so maybe something is wrong with the upgrade, but also pointing more to the MMU. That 74LS158N that has all the wires soldered to it may also be suspect, and is a common part.

 

I think I'd start by removing/socketing/swapping out the CO61618 chip (XL/XE MMU). Its soldered to the motherboard, so be super-extra careful when desoldering it from the notoriously delicate XE PCB's... Best practice for testing for a bad chip is to try the suspected bad chip in the otherwise working computer. If you don't have another 600 or 800XL or XE to 'borrow' one from, I can program a GAL to replace it and mail it to you.

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Thanks for offering to mail me an MMU! The 800 (non-XL) doesn't have the right MMU, correct? They don't seem to be that expensive from Best Electronics, so I will probably just buy one. If it doesn't end up fixing the problem, it definitely won't hurt to have a spare as replacement parts get harder to find.

 

When soldering, what temperature would you recommend to prevent burned traces?

 

Thank you for your help

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A 600XL, 800XL, 65XE or 800XE MMU will be compatible in the 130XE. 400, 800, 1200XL, XEGS are not.

 

Getting it from best electronics will be fine, if you buy enough to make the minimum order.

 

I'll let others comment on specific soldering temps, as my own soldering iron is just a simple 20/40 watt iron, and mechanical solder sucker. I just try to keep contact times to a couple seconds max at a time, and never force the chip out if its still "stuck" after desoldering. You can help each pin free by wiggling the pin with a screwdriver while heating the pin with the soldering iron.

 

(Xmas may improve my desoldering tool situation to do more than 1 or 2 chips in an evening. :) )

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22 minutes ago, Nezgar said:

Xmas may improve my desoldering tool situation to do more than 1 or 2 chips in an evening. :)

I’ve had this for 18 months and it has changed my (electronics) life. :)

 

As for soldering temp, I tend to go between 700F - 750F, but (and this is a big “but”), I’ve done quite a bit of work on my Ataris in the last 5+ years and I have developed a very good feel for what’s needed to solder and desolder a component. Make no mistake, there’s a bit of an art to it. But having said that, and specifically with regard to desoldering a chip off an XE board, there’s one rule you really shouldn’t try to break: always add fresh leaded solder to each leg of a component you wish to remove before using your desoldering tool (whether solder sucker, desoldering pump, whatever). The fresh solder adds fresh flux and the process of adding it heats up and melts the old solder, heats up the via gently, and makes the hole much easier to clear. 

 

0C645348-31C1-4DF0-B1A6-46F7FE7B7094.jpeg

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1 hour ago, DrVenkman said:

I’ve had this for 18 months and it has changed my (electronics) life. :)

Cool, that is actually the exact model that a buddy of mine got, and I have forwarded a link to my wife. so that's 2 endorsements :) I've seen some videos on youtube of some $100-$150 china brands, but probably better to just get the real thing and avoid any possible grief. :thumbsup:

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I had to remove chips in my 130XE when I did my U1M upgrade, I use a temperature controlled Maplin soldering iron I bought

some years ago before they went bust and my trusty old "Solderpult" I've had for over 30 years.

 

The key to success is as DrVenkman says, a bit of fresh solder on the iron makes for a quick easy removal.

Don't linger on a joint if it doesn't seem to melt quickly, take the iron off, clean the tip and try again.

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9 hours ago, Nezgar said:

Cool, that is actually the exact model that a buddy of mine got, and I have forwarded a link to my wife. so that's 2 endorsements :) I've seen some videos on youtube of some $100-$150 china brands, but probably better to just get the real thing and avoid any possible grief. :thumbsup:

Make that 3 endorsements. I don't have too much experience working with hardware, and hearing horror stories of traces coming off, I decided to get one. I have removed 3 components pretty easily without any issues. It was way more than I wanted to spend, but stopping or mitigating the damage I can cause won me over.

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16 hours ago, DrVenkman said:

I’ve had this for 18 months and it has changed my (electronics) life. :)

 

As for soldering temp, I tend to go between 700F - 750F, but (and this is a big “but”), I’ve done quite a bit of work on my Ataris in the last 5+ years and I have developed a very good feel for what’s needed to solder and desolder a component. Make no mistake, there’s a bit of an art to it. But having said that, and specifically with regard to desoldering a chip off an XE board, there’s one rule you really shouldn’t try to break: always add fresh leaded solder to each leg of a component you wish to remove before using your desoldering tool (whether solder sucker, desoldering pump, whatever). The fresh solder adds fresh flux and the process of adding it heats up and melts the old solder, heats up the via gently, and makes the hole much easier to clear. 

 

0C645348-31C1-4DF0-B1A6-46F7FE7B7094.jpeg

What make is that, can't quite make it out ?

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For anyone who can't afford or can't justify the Hakko, this is a good cheap alternative:

 

The ZD-915 was on offer from one reputable vendor for 55 GBP or so a few months back.

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Hello guys

 

In Germany you can get what they call "Löthonig" (which literally translates to "solder honey") which essentially pure solder flush.  Some people swear by it.  I don't (de)solder that much, but AFAICR it's better than adding extra solder.

 

Sincerely

 

Mathy

 

 

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For the hobbyist not professional, this tool DOES the job:

(it requires 220V)

AliExpress

1973945879_Solderingtool.thumb.jpg.8c69fbfbc63a9a812bff779a450343d8.jpg

 

Edited by tane

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As a student, at my university I have access to some fairly nice soldering/desoldering equipment for free, so I probably won't need to buy anything fancy at the moment.

 

That Hakko seems really nice, but I suspect it will be a few years before I can afford to spend that much on a tool. I will definitely keep the ZD-915 in mind though, in case I want to work on projects over the summer--£55 is definitely much more in my price range.

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Hello tane

 

1 hour ago, tane said:

For the hobbyist not professional, this tool DOES the job:

(it requires 220V)

AliExpress

1973945879_Solderingtool.thumb.jpg.8c69fbfbc63a9a812bff779a450343d8.jpg

 

 

And the correct power socket.  And enough patience.

 

Just visite your local electronics store.  They will sell you a quality product that you can take with you as you leave the store, but before you do, they may even give you some advice for free.  Best thing is, you can take it out of it's box right after you get home and it'll plug into any of the power sockets in your home and work without adaptor.  Plus you'll be supporting a local business.

 

Sincerely

 

Mathy

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20 minutes ago, Mathy said:

Just visite your local electronics store.

That presumes such a place exists. It doesn't in my city, nor in many cities, towns and smaller communities around the world. And I live in a metropolitan area with 1.5 million people within a 45 minute drive.

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Yes: I'm sure one of the last remaining UK high street electronics vendors (Maplin, before they went bust) would have happily bent the customer over and sold them a Chinese tool at twice the online price. :)

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31 minutes ago, Mathy said:

And the correct power socket.  And enough patience.

It's part of the fun. Still it's the cheapest option for someone new to electronics.

 

33 minutes ago, Mathy said:

Plus you'll be supporting a local business.

I'm not a garlic fan, but nothing to do with undervalued currencies and incompetent governments.

 

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18 minutes ago, flashjazzcat said:

Yes: I'm sure one of the last remaining UK high street electronics vendors (Maplin, before they went bust) would have happily bent the customer over and sold them a Chinese tool at twice the online price. :)

talk about being hoist on their own petard - they (Maplin) shaft the customer with stupid levels of overcharging "own brand" (aka re-badged Far-eastern) hardware. the customer in turn shafts Maplin back by going direct to the supplier. karma. 😊

Edited by brenski
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So, the first 16KB is testing OK... and the 2nd 16KB is predominabtly bad.
 
Try to boot the computer with the OPTION key held down, you should see 8 more memory test squares in the bottom row, (because it disables the 8K BASIC ROM, freeing up 8KB more RAM) but I suspect those all test green as well.
 


I booted with the option key held down and all the additional squares were green. Additionally, I was able to boot the Star Raiders cartridge and play as if nothing was wrong.

Sent from my SM-N950U using Tapatalk

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5 hours ago, kb3wmh said:

I booted with the option key held down and all the additional squares were green. Additionally, I was able to boot the Star Raiders cartridge and play as if nothing was wrong.

OK good.. so this just points further away from the base 64K RAM being faulty, and towards the MMU or the or mod.

 

Star Raiders will run with only 8K of RAM, so it works just fine because it doesn't touch the memory area that is faulty.

 

Edit: Does anyone think it could be the EMMU (CO25953) or FREDDIE (CO61991)? Looks like the EMMU can also be programmed to a GAL16V8 like the MMU, if socketed it would fill the unoccupied 4 through-holes: https://www.atarimax.com/jindroush.atari.org/achemmu.html I've made a working XE/XE MMU with a GAL16V8, I haven't tried making an EMMU yet.

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