130XE Help needed

[Dropcheck]

Hi everyone,

 

New to Atari 8bit after a 20 year hiatus. I picked up a 130XE on ebay that the seller of course claimed was in working order. It came in today and of course I rushed to connect it up to my tv. Surprise! It won't boot up. Comes up with a red screen, buzzing sound and no Basic ready prompt. Tried a game cart. Same thing. Any ideas before I go tearing into the case.

 

Thanks,

[Urchlay]

About all you can check without cracking the case is the power supply voltage. I don't know what the PSU voltage/pinout is for the 130XE, but it's in the Atari 8-bit FAQ. Most likely, it'll read a couple volts high with no load on it (the 800XL PSU does this: it's a 5V supply under load, but reads 8-9V with no load). If it reads low, or has the wrong polarity, it needs to be replaced (and with luck, a new PSU will make the 130XE work).

 

The only other possibility to check before opening the case is to make sure there's no junk inside the cartridge or ECI (parallel bus) ports. It's at least possible that a little piece of something conductive might get lodged in one of the ports, though kind of unlikely.

 

If you end up having to get inside the case... it's not fun doing chip-swapping on the XE machines, because the chips are always soldered (never socketed). A red screen with buzzing might mean a bad ANTIC, 6502, or POKEY... a black screen with no sound usually means one or more bad RAM chips. However, the #1 most likely thing to fail on an XE (so I have been told) is the RAM. On a 130XE, there are 2 banks of 8 64Kx1 RAM chips. You can try swapping them, which may let it boot, but in that case the extended RAM won't be good, and any software that tries to use it (RAMdisk drivers mostly) will fail. Plain old DOS 2.0/2.5 should be able to boot though, and built-in BASIC should be fine if you don't have a disk to boot.

[Dropcheck]

Hi,

 

Well I finally got brave enough to open the case. (Read I settled with the ebay seller) Someone definitely had been inside before me. Looks like they were trying to fix the problem. I found several jumpers and two chips socketed, I believe the cpu and pokey chips. On closer exam I found two wires going to the 74LS08P (U18) chip to the upper right of the pokey chip as you are facing the front of the 130xe. On that chip I found pins 9 & 10 with a solder bridge connected to the purple wire. Now I haven't had much experience moding the 130XE. Kinda stayed away from it with a passion. But I don't think that solder bridge should be there. I can't find U18 on the 130xe schematic diagram I have. Does anyone have an idea?

 

I am posting a trio of pics. Sorry for the resolution. I know it looks kinda fuzzy. My little digital camera just can't handle the closeups very well.

 

 

[classics]

Those modifications are normal for a 130XE, they were applied at the factory.

 

Steve

[Rybags]

You sure that's pins 9,10 of the 74LS08?

 

According to the datasheet, those two pins are inputs for one of the AND gates. Wouldn't make sense really.

 

Lots of Atari stuff has wiring on the board which looks like an afterthought or mod, but is actually that way from the factory. It's been a couple of years since I opened my 130XE, so I can't really remember.

 

Hopefully, someone else might come along with pictures, or an explanation.

 

I see no sense in a mod playing with those chips unless someone has performed a RAM expansion.

 

What type of RAM chips does your board have?

[Dropcheck]

Hi,

 

Now you've made me go look at it again. Yes it's 74LS08P (U18). I believe you number from the right front of the chip, so this would be pins 9 & 10. I thought almost all chips were solder, not socketed on the 130XE. I'm not complaining, just surprised to find the cpu and pokey socketed. Thought this might have been done in a repair. The memory chips are marked MT4264-15 USA and do not appear to have been disturbed. I think I remember someone saying these were not the best memory chips....was it MetalGuy66?

[re-atari]

Now you've made me go look at it again. Yes it's 74LS08P (U18). I believe you number from the right front of the chip, so this would be pins 9 & 10. I thought almost all chips were solder, not socketed on the 130XE. I'm not complaining, just surprised to find the cpu and pokey socketed. Thought this might have been done in a repair. The memory chips are marked MT4264-15 USA and do not appear to have been disturbed. I think I remember someone saying these were not the best memory chips....was it MetalGuy66?

The 2 wires are indeed put in at the factory. Here is a hires photo of an unmodded PCB, so you can check for yourself.

 

 

On DIL IC's numbering of pins is anti clockwise, starting with the first pin to the left of the notch on the short side of the housing. By the looks of your photo (it is really fuzzy) pins 8, 9 and 10 are indeed connected together by a blob of solder. The photo above clearly shows these pins are not soldered together with that particular PCB.

Here is (part of) the 130XE's schematic containing U18 (top left).

 

 

Looking at the way this AND-port is wired, it seems to me its only purpose is to provide a timing delay. The solder blob connects the port's input and output, in effect circumventing this timing delay. This may well have been done at the factory, as IIRC there was a specific production run of the GTIA that contained a bug. These faulty IC's were all used in a specific batch of the 130XE. Maybe this was a way of getting a computer that failed quality control back to the specs again. I don't have more precise details about this, I just remember reading about it. Can anybody fill me in on this?

 

Like Urchlay suggested, I'd start by swapping the DRAM's. M(icron) T(echnology) built DRAM's are the #1 cause of failing XE's. DRAM's failing by an open circuit can be checked by piggybacking a known good same component (but mind the orientation). If a DRAM fails by a short circuit there really is no way around desoldering it and putting in a (socketed) replacement. After identifying the culprit(s), it is wise to replace the other DRAM's as well, just in case. By all means put in sockets. If you have a chance, buy Japanese built replacements; when treated properly they almost never fail. Speed is not an issue. 100ns to 150ns will be just fine, 200ns will work as well.

In the past months there have been a number of threads dealing with defective XE's that all turned out to have faulty DRAM's. Search for the ones by Urchlay, Tezz and Mimo, you will more than likely find ideas to check your XE.

 

re-atari

Edited June 20, 2007 by re-atari

[mimo]

yep, try the Ram first, I found the way that works best for me is to use some micro snippers and cut the legs off the ram, then use de-solder wick to remove the remains and clear the holes.

solder in sockets

put the ram in the sockets.

I think it took me about an hour the first time I did it (and that was with no previous soldering experience!

 

I have now bought 4 Atari's back from the dead just by replacing the RAM

 

good luck

[Urchlay]

yep, try the Ram first, I found the way that works best for me is to use some micro snippers and cut the legs off the ram, then use de-solder wick to remove the remains and clear the holes.

 

Do you do this after finding which RAM chip is bad, or do you replace all of them when you do this? Shouldn't cut the legs off the ones that aren't bad...

 

Or are those MT-brand RAMs in the 130XEs so horrible that they're not worth salvaging?

[Dropcheck]

Thanks re-atari

 

I think I am convinced that replacing the ram is the best place to start on getting my 130xe up and running. I'll order chips and sockets from Jameco tonight. Been thinking about doing Peterson's 130xe -> 320k mod anyway. Also have a 800XL that needs a little more helping of memory too.

[mimo]

yep, try the Ram first, I found the way that works best for me is to use some micro snippers and cut the legs off the ram, then use de-solder wick to remove the remains and clear the holes.

 

Do you do this after finding which RAM chip is bad, or do you replace all of them when you do this? Shouldn't cut the legs off the ones that aren't bad...

 

Or are those MT-brand RAMs in the 130XEs so horrible that they're not worth salvaging?

the 130 xe motherboard is sort of weak, so I just try and take care of the board as much as I can, this is the kindest method I know of.

Also the RAM in the 130's is real crap, so if you dont replace it now, chances are you will be doing soon.

cost to socket and replace all the RAM is about £10, but I bet you can do it cheaper in the US (everything is cheaper in the US)

to be honest, I couldnt be bothered trying to find the bad ones.

but you are right, I probably should save the Ram that is good, now my soldering/de-soldering is getting better I probably will next time

Edited June 20, 2007 by mimo

[Urchlay]

the 130 xe motherboard is sort of weak, so I just try and take care of the board as much as I can, this is the kindest method I know of.

 

Someone here once talked about buying or making an IC-desoldering tool... basically a U-shaped piece of metal that replaces the tip on a soldering iron, and which heats up all the pins at once, so you can just pull the chip out from the other side when the solder melts. That's probably kind to the board and to the chip... wonder how hard it'd be to make one?

 

Also the RAM in the 130's is real crap, so if you dont replace it now, chances are you will be doing soon.

 

Well, if it's that bad, I guess it's not worth trying to save the "good" chips.

[+Guitarman]

Someone here once talked about buying or making an IC-desoldering tool... basically a U-shaped piece of metal that replaces the tip on a soldering iron, and which heats up all the pins at once, so you can just pull the chip out from the other side when the solder melts. That's probably kind to the board and to the chip... wonder how hard it'd be to make one?

 

Here is an auction for one. He has them on quite frequently.

 

Desoldering tip for 14-Pin & 16-Pin DIP IC's

[Dropcheck]

Someone here once talked about buying or making an IC-desoldering tool... basically a U-shaped piece of metal that replaces the tip on a soldering iron, and which heats up all the pins at once, so you can just pull the chip out from the other side when the solder melts. That's probably kind to the board and to the chip... wonder how hard it'd be to make one?

 

Here is an auction for one. He has them on quite frequently.

 

Desoldering tip for 14-Pin & 16-Pin DIP IC's

 

 

Thanks Guitarman,

 

Guess I'll spend some more money on ebay.

[Dropcheck]

Part II

 

Well I missed the auction. Some whippersnapper bought it out from under me. Drat! So I guess I get to do it the hard way.

 

Not strictly related but I was able to fix a broken 1050 that came in on another auction. Turned out to be the 2793 FDC chip. I was afraid of that. Seems they are around $15 smackers at Best Electronics. Anyone have an extra one laying around that works they don't need?

 

Now let's see I need 16 sockets, 16 4256.......

[Defender II]

 

<© 200707011640CSTPJB> Do not reproduce this in whole or in part without my permission.

NOTE: THESE ARE TECHIE SECRETS, DO NOT READ!

 

Checking your power supply & cables is a must.

 

BEFORE attempting any repairs, do a thorough inspection of the entire board for any components that are cracked, bulging, or discolored/burnt. Believe it or not, you can even use your nose to smell burned components. Look for any cracks in the circuit board or shorts between components and runs. Verify everything with your schematics. If it all looks & smells right then look again. If you still don't find anything proceed…

 

It is very easy to de-laminate the pads & runs on circuit boards, especially the 130XEs.

If you are VERY good at de-soldering, then by all means go for it. The multi-pin de-soldering tips work OK but I prefer a real de-soldering station. For those of you brave enough to proceed without a de-soldering station or multi-pin tip…

 

Buy a good solder sucker, with a metal cylinder and replaceable composite heat-resistant tip. Buy a good soldering iron with grounded tip.

 

I have replaced 40 pin chips with the following method, but you must be very careful not to overheat the connection or you will damage the board and/or chip, thus wasting the time you spend removing it this way...<see ! below>

 

Work on circuit boards at you own risk, especially if you don't have proper ESD protection for their components. If you do then great! ALWAYS practice de-soldering on a scrap board first, like one of those 40 pin keyboard chips on an old IBM clone motherboard.

 

TAKE YOUR TIME!!! If you don’t know the difference between plumbing solder & solder for electronics don’t start…

 

Ground yourself (morally & electrically) to dispel evil & static electricity. Wear eye/face protection, shoes, long sleeve shirt and long pants. Soldering naked will only lead to blindness or other burns, as hot solder is a heat seeking missile for bare skin.

Make sure you have a good soldering iron, solder sucker, small flat blade jeweler’s screwdriver, needle nose pliers, diagonal cutters, and solder for electronic circuits.

 

<For de-soldering, rosin-core solder works better than solid, but don’t forget to clean up the residue with isopropyl alcohol on a cotton swab then with water on a cotton swab>

 

Place the circuit board in a stand so you have access to both sides of the board and so you can use both hands. Make sure your iron is clean & hot. Compress the solder sucker.

Place a small dab of solder on the tip of the iron. Wipe it off on a damp sponge; I said a SMALL dab of solder. Again place a SMALL dab of solder on the tip.

With the solder sucker in your weak hand and the iron in you dominant hand, touch the dab of solder on the tip of the iron to the joint of the pin AND pad to be de-soldered.

AS SOON AS the solder between the pin AND pad liquefies put the sucker tightly over the pin and iron tip and release the suction. OK, this time try compressing the solder sucker first like I said & do it again.

Inspect the pin and pad. If you de-soldered it correctly the pin, pad & hole will be clear of solder. If you took too long, the pad/run may have lifted from the board and you may have damaged the component as well.

If the pin, pad, & hole are not completely clear of solder, then re-solder the connection, but don't put too much solder! Try again.

OK 14, 16, 28, 40 pins later...you have cleared all the pins, pads, & holes of solder. Hooray, you are lucky and your component falls onto the floor, and you step on it in your excitement. ...

 

More likely than not, one or more pins will hang. This can be a small amount of solder or a bent pin. Inspect the holes for bent pins and straighten them out, usually they will still have some solder holding them and you can use the small flat screwdriver to lift them as you touch the tip of the iron to them, with a SMALL dab of solder. De-solder any pins found still sticking after straightening, by first re-soldering, then de-soldering.

 

The following takes coordination, if you don’t have any skip to <!> OK you did all that and a pin is still stuck. Look at the pin. It will be against one side of the hole or the other, usually away from the component. On the component side of the board, apply a small amount of pressure to the pin to force it away from the side of the hole, at the same time touch the tip of the iron to the pin on the other side of the board, you will feel it let loose, then quickly remove the iron. All pins should now be loose and the component free.

 

Oh, you weren’t able to get it out that way… Hmm… one last try, very dangerous ‘tho,

NOT RECOMMENDED, but works %50 or better depending on the techie…

Inspect each pin, with the flat bladed screwdriver, gently press against them one at a time on each side to wiggle the pin and find which pins are still sticking. <Don’t wiggle them too much or the pin will break>

Once you have determined which pins are still sticking… Start with the sticking pin closest to one end of the IC, place a flat bladed screwdriver blade under the chip as far as it will go without forcing it, then touch the sticking pin with the hot soldering iron, at the same time gently torque(don’t pry) the screwdriver so the blade lifts the side of the chip with the sticking pin and it should let loose. Continue until all pins on one side are loose, then do the other side.

 

! If you have any qualms about it, then the safest way is to cut the old chips out one lead at a time with a diagonal cutter. Next de-solder each leg by itself.

 

After all that work installing sockets is a must!

<© 200707011640CSTPJB> Do not reproduce this in whole or in part without my permission.

Edited July 2, 2007 by Defender II

[MEtalGuy66]

The only thing I would add to that is that if you use the soldering iron to heat the joints from the COMPONENT SIDE, and watch for the solder to liquify on the SOLDER SIDE, you can actually place the solder sucker directly over the joint, and get a good "seal" with the board, and suck the holes much cleaner, with much fewer attempts. As he said, have your solder sucker "cocked and ready" before you begin heating the joint. Also, if you are going to heat the component side, its probably good to use a temp-controlled iron, set no higher than about 600 degrees (for the chips' sake).

 

I have been socketing 130xe boards since the early 90s. I have tried every method of desoldering he described, and a few more. The one he is describing with the iron and a spring-loaded solder sucker is by far the most productive. I can do an entire board (yes including all 16 ram chips and even the small ICs) in less than 6 hours, without damage to a single trace or pad. And that is removing all the ICs and installing new sockets.

 

I have a hakko electric desoldering gun, which works fine, but does not get the holes nearly as clean and free of solder. I have used the "IC TIPS" that do all the pins at once, but the problem here is that a) You need a seriously hefty wattage iron, and b) you STILL have to go back and evacuate each hole of solder before you can do a decent job of installing a socket. The radio-shack "squeeze bulb" type desoldering iron is about worthless as well. I have used large bench-mounted desoldering stations at the tech school I attended, and as I recall they were quite good, but they are also beyond the budget of what I have ever been willing to spend.

 

 

Another thing I would add, is make sure you use decent sockets. Get the 3m or tyco style that have "double wipe" contacts. These style sockets have "brushes" that contact the pin leg of the chip from both sides. Also, in this style socket, the actual solder legs or "pins" of the socket, itself, remove from the top, instead of from the bottom. What this means is that the socket cant come off of the board, leaving the pins behind. I know this is an extreme case scenario, but I have seen it happen on occasion when someone "got shitty" with it. heh.

 

Last thing.. Once you have the nice new sockets installed, use your iron to clean any excess solder from the chip pins BEFORE you insert them in the socket. otherwise, the next time you remove the chip, its likely to seriously screw up the contacts in the socket, because they will hang up on the chip pins as you pry the chip out.

[Defender II]

I agree with MEtalGuy66 on placing the iron on the component side of the board and the solder sucker completely covering the pin, but this does increase the chance of heat damage to the component, so a heatsync would be recommended. I use a small alligator clip for this purpose. Also those whole chip tips can cause heat damage as well and are best used for removing chips you don’t plan on reusing, therefore the clip & replace method is cheaper than buying one of those and frying the chip anyway. Professional de-soldering stations work well, but do clog with solder and require regular maintenance, so along with the cost they aren’t recommended except for someone who needs one on a regular basis. In my opinion the bulb suckers are not very useful for desoldering.

[Dropcheck]

Hi everyone,

 

Thanks for the info. I was a minuature electronics repair tech in the Navy for a number of years so I know my way around with a soldering iron and a circuit board. But I haven't done much of that in the last six years of civilian life so I'm a little rusty. I think I'll do the clip and replace method. I think it will be faster. I don't plan to reuse the memory chips anyway. I don't have a solder sucker either. Tried them in the Navy and I never could get the d*#@ things to work. I was told I was the problem, but I never would believe it.

 

Thanks for the tip on the sockets MEtalGuy66. Do you know where I could get them? Would Jameco have them?

[MEtalGuy66]

Jameco has them, but I prefer to order from mouser or digikey because they are a few cents cheaper, and also, they have links to datasheets/mechanical drawings so you can se exactly what you are getting. Alot of times you cant tell from a photo what kinds of contacts are in a socket.