Oxidized 800XL keyboard traces

[Urchlay]

A donor XL always comes in handy as a supplier of spare parts Shops generally tend to be closed at the very moment that you need spare parts, preventing you from tinkering on...

If you want to resurrect the 600XL in the future, it's good to know that you're not restricted to using a 6520 as a replacement for PIA. A 6821 will do just as well (talking from experience).

 

Hm, I have a couple of VIC-20's I'm not using... looks like they have 6520's I could borrow.

 

Upgrading the 600XL to 64K is easy, though it may be difficult to find the 41464 (64k * 4bit) DRAM's. Cannibalizing an old EGA or VGA card may be the way to go.

 

Fixing/upgrading the 600XL is a future project for now... If I can get both these 800XL's working, I'll be happy. Actually, I got one working already, and am happy... if I get the other one working I'll be ecstatic

 

That's resistor R32 (3k Ohm) I was referring to in my earlier reply. The left hand solder pad is connected to 5V, the right hand one to the 4164's pin 1. In the standard XL layout this resistor defines a high level on this pin (refresh). In the upgrade it has to be removed (well, just desoldering the right hand terminal will do as well) to provide a spot to link A8 to the 41256's. If you leave R32 in place, the XL can not pull A8 to a low level, which in effect means that it 'sees' only 64K.

 

Ah! OK, so I've already determined that a stock 800XL can use 256K DRAMs (only uses 64K of them of course). My upgraded 800XL has one bad RAM chip... if I can't find a 256K chip to replace it with, I should be able to replace it with a 64K instead, put R32 back, and just remove the upgrade (and replace the bad PIA with the one from the 600XL). That ought to give me a 64K 800XL.

 

I already tried this, except for replacing R32. It didn't boot... but without either R32 or the upgrade board, A8 would be floating, which would cause it to randomly be 0 or 1, right?

 

How critical is the value of R32? Can I use something like a 2.2K or 4.7K, or does it *need* to be 3K?

[Urchlay]

Update:

 

Thought I had the keyboard key heights fixed last night, but that was just wishful thinking combined with tiredness.

 

I was wrong about the keyboard inserts. They are all the same height. The reason some of the keys are taller than their neighbors seems to be that I stretched the springs when removing the keys.

 

Unfortunately, those 10-12 keys I removed whose inserts came out with them, are scattered all over the keyboard. It looks... mountainous.

 

Moral of the story: if you want to clean the keys on an 800XL keyboard, leave them on the keyboard and just scrub between them with a q-tip or a toothbrush. Never, ever remove the keycaps...

 

If there were a reliable way to remove *just* the keycaps, that'd be OK, but there's no way to keep the key inserts from coming out with 'em sometimes (you won't feel it happening, you won't know it until you remove the whole thing and see a couple of springs instead of a white plastic insert).

 

So I guess the 600XL will be donating a keyboard, too

[re-atari]

Hm, I have a couple of VIC-20's I'm not using... looks like they have 6520's I could borrow.

 

IIRC (can't check as I don't own a VIC20 or a C64), these don't contain PIA's (6520), but VIA's (6522) and CIA's (6526). Search the web for schematics before hand, it will save you the effort of opening one up in vain. Besides that, as VIC20's and C64's are of Tramiel origin, I'd not at all be surprised to find every component soldered in instead of socketed. Desoldering a 40-pin IC is tricky, but it is feasible (again talking from experience).

 

I already tried this, except for replacing R32. It didn't boot... but without either R32 or the upgrade board, A8 would be floating, which would cause it to randomly be 0 or 1, right?

 

How critical is the value of R32? Can I use something like a 2.2K or 4.7K, or does it *need* to be 3K?

 

I personally have never put 41256's in a stock 800XL, but I don't see why it wouldn't work. I imagine that if A8 is not pulled high, memory addressed by it may contain garbage from initialization after powering up, which in its turn prevents the XL from booting up and so getting into selftest.

 

The value for R32 is not critical at all, as long as it's over 2.2K. 4.7K will do just as well, but I wouldn't go higher than 10K. The function of the resistor is to define 5V, or high level, at pin 1 (refresh), but it also draws a little current which the PSU has to deliver. And, the lower the resistance, the higher the current it draws, and therefore the higher the required wattage the resistor has to be. At 2.2K a 1/8W type will do just fine.

 

If installing R32 doesn't lead to success, I wouldn't spend any more time on this route, but instead just get my hands on a replacement 41256. Cannibalize it from an old PC or 286 mainboard, if you have one laying around.

 

Regarding your 600XL's keyboard, I've read (not sure where, though) that all 600XL's were delivered with an ALPS keyboard instead of the dreaded foil ones. If you're thinking of swapping keyboards, IMHO it makes the choice which one will go in which machine a bit easier

 

re-atari

[Urchlay]

Hm, I have a couple of VIC-20's I'm not using... looks like they have 6520's I could borrow.

 

IIRC (can't check as I don't own a VIC20 or a C64), these don't contain PIA's (6520), but VIA's (6522) and CIA's (6526). Search the web for schematics before hand, it will save you the effort of opening one up in vain. Besides that, as VIC20's and C64's are of Tramiel origin, I'd not at all be surprised to find every component soldered in instead of socketed. Desoldering a 40-pin IC is tricky, but it is feasible (again talking from experience).

 

Yeah, I spoke too soon... had found a bit of Vic-20 documentation that had a typo, referred to the 6522 as a 6520. A bit more searching straightened me out...

 

I personally have never put 41256's in a stock 800XL, but I don't see why it wouldn't work. I imagine that if A8 is not pulled high, memory addressed by it may contain garbage from initialization after powering up, which in its turn prevents the XL from booting up and so getting into selftest.

 

The value for R32 is not critical at all, as long as it's over 2.2K. 4.7K will do just as well, but I wouldn't go higher than 10K. The function of the resistor is to define 5V, or high level, at pin 1 (refresh), but it also draws a little current which the PSU has to deliver. And, the lower the resistance, the higher the current it draws, and therefore the higher the required wattage the resistor has to be. At 2.2K a 1/8W type will do just fine.

 

For the record, 41256's (or the 81256's I have, same thing) do work in a stock 800XL, or at least they do in mine. I get 64K of RAM, of course, they just act like 4164's.

 

I'm more likely to have either a 2.2K or a 4.7K than a 3K (bought one of those "assorted resistors" packs from Rat Shack).

 

If installing R32 doesn't lead to success, I wouldn't spend any more time on this route, but instead just get my hands on a replacement 41256. Cannibalize it from an old PC or 286 mainboard, if you have one laying around.

 

Well, I used to keep old boards around, but threw a bunch of them out last year in an effort to clean the place up some

 

If I had to though, I could desolder one from my 520ST. Am about to go to a friend's place to look through his collection of 286-era parts, which are conveniently sitting in a box in the living room floor (he's just moved in to his place).

 

The reason I want to try with R32 and without the upgrade board is that I have no way to test the 3 ICs on the upgrade board. I suspect one or more is bad just because the 800XL was killed by overvoltage (12V supply where 5V should go), and I know that one RAM chip and the PIA are both bad... those 2 bad parts are connected to each other via the upgrade board, so there's a strong chance it got fried too. I'd be happier with a full 256K, but if I get it working as a 64K XL, it'll be a major improvement over its current "doorstop" status

 

Regarding your 600XL's keyboard, I've read (not sure where, though) that all 600XL's were delivered with an ALPS keyboard instead of the dreaded foil ones. If you're thinking of swapping keyboards, IMHO it makes the choice which one will go in which machine a bit easier

 

My 600XL has the mylar foil keyboard

 

Either whoever said that was mistaken, or my 600XL's keyboard got replaced some time in the past, which I doubt: all the screws were factory-tight, and the RF shield clamps were perfect 90 degree angles. The 600XL's console keys stick, too (they're not touching the sides of the case, they press fine, but they don't release).

 

Have been considering removing ALL the key inserts from the 800XL keyboard. The keys that are too tall, still work just fine. If I remove them all and put them back, they'll all be too tall, and maybe match better than they do now. That, or leave it as-is: the unevenness is not really noticeable when typing, it just looks weird... but I showed it to someone else and he didn't notice until I made him stare at the keyboard for a full minute. Maybe I should quit while I'm ahead, on that 800XL: it's working great right now.

[re-atari]

For the record, 41256's (or the 81256's I have, same thing) do work in a stock 800XL, or at least they do in mine. I get 64K of RAM, of course, they just act like 4164's.

 

I'm more likely to have either a 2.2K or a 4.7K than a 3K (bought one of those "assorted resistors" packs from Rat Shack).

I'm pleased to hear my intuition proves to be right in real life 3K is a rather unusual value, a 4.7K will do the trick.

 

If I had to though, I could desolder one from my 520ST. Am about to go to a friend's place to look through his collection of 286-era parts, which are conveniently sitting in a box in the living room floor (he's just moved in to his place).

If these are 8 or 10Mhz boards, you have a good chance of finding suitable DRAM's (if your friend hadn't already picked them clean in the past, that is). Those boards usually had either 640K (18 41256's and 18 4164's) or 1M onboard (36 41256's), and the good news is, they were by and large always socketed. This was due to a couple of Japanese DRAM fabs that were badly damaged in an earthquake in 1988, which lead to a big shortage in supply. DRAM prices went through the roof in no time (like 500%! in just a few days) on the spotmarket, though a lot of this was caused by speculators. Manufacturers treated DRAM's as precious stones. When socketed they could easily be removed from mainboards that fell through in the manucaturing process, and 'recycled' onto others.

By the time the 12Mhz boards hit the market round 1990, highly integrated chipsets appeared (anyone remember ' Chips & Technologies' ?), and manufacturers that used them switched to 30-pin SIPP and a bit later to SIMM modules in a record breaking time.

 

The reason I want to try with R32 and without the upgrade board is that I have no way to test the 3 ICs on the upgrade board. I suspect one or more is bad just because the 800XL was killed by overvoltage (12V supply where 5V should go), and I know that one RAM chip and the PIA are both bad... those 2 bad parts are connected to each other via the upgrade board, so there's a strong chance it got fried too. I'd be happier with a full 256K, but if I get it working as a 64K XL, it'll be a major improvement over its current "doorstop" status

I think I read they are LS158's, right? Like the CD4051's those are readily available as well, costing maybe 1$ each.

 

Either whoever said that was mistaken, or my 600XL's keyboard got replaced some time in the past, which I doubt: all the screws were factory-tight, and the RF shield clamps were perfect 90 degree angles. The 600XL's console keys stick, too (they're not touching the sides of the case, they press fine, but they don't release).

Sorry to hear you have a foil keyboard. You should get the console keys to travel freely again by loosening the 4 screws that hold the keyboard plate in the upper case, and shifting it a bit. Strange thing is, only last weekend I read about a similar case in http://www.atariage.com/forums/index.php?showtopic=108031 by KrazyKaiju. Looks like it did the trick for his XL.

 

Have been considering removing ALL the key inserts from the 800XL keyboard. The keys that are too tall, still work just fine. If I remove them all and put them back, they'll all be too tall, and maybe match better than they do now. That, or leave it as-is: the unevenness is not really noticeable when typing, it just looks weird... but I showed it to someone else and he didn't notice until I made him stare at the keyboard for a full minute. Maybe I should quit while I'm ahead, on that 800XL: it's working great right now.

I think you're being a perfectionist Classic car owners usually have a similar same state of mind about only slight imperfections. I'd say the other XL's need your attention right now. Keep us informed about your progress and the quirks you meet.

 

re-atari

[Urchlay]

If these are 8 or 10Mhz boards, you have a good chance of finding suitable DRAM's (if your friend hadn't already picked them clean in the past, that is). Those boards usually had either 640K (18 41256's and 18 4164's) or 1M onboard (36 41256's), and the good news is, they were by and large always socketed. This was due to a couple of Japanese DRAM fabs that were badly damaged in an earthquake in 1988, which lead to a big shortage in supply.

 

I remember when that happened. I had a 520ST I wanted to upgrade to 1 meg, and the prices for the RAM were outrageous.

 

He couldn't remember where his 286 motherboard stash is, I got a big box of ISA cards... found 2 or 3 of them with 4464's (64Kx4 DRAMs), which aren't useful for the 800XL, but will come in handy someday when I upgrade the 600XL to 64K. Apparently that mod consists of 2 4464's and 3 jumpers, no extra logic chips or anything.

 

The reason I want to try with R32 and without the upgrade board is that I have no way to test the 3 ICs on the upgrade board.

 

I think I read they are LS158's, right? Like the CD4051's those are readily available as well, costing maybe 1$ each.

 

I said they were 74LS158's, but I looked at them again after a good night's sleep... one's a 158, the others are a 74LS139 and a 74LS153. I found a 153 on one of those ISA boards, but not socketed. There are a couple of places left around town where I might be able to get 74xx series chips and possibly DRAMs, if I don't mind driving. Could order from Jameco/Digikey/etc too, but I'd rather drive for a couple hours than wait a week for delivery

 

Sorry to hear you have a foil keyboard. You should get the console keys to travel freely again by loosening the 4 screws that hold the keyboard plate in the upper case, and shifting it a bit.

 

Yah... means it's probably not worth swapping keyboards though.

 

Have been considering removing ALL the key inserts from the 800XL keyboard... Maybe I should quit while I'm ahead, on that 800XL...

I think you're being a perfectionist Classic car owners usually have a similar same state of mind about only slight imperfections. I'd say the other XL's need your attention right now. Keep us informed about your progress and the quirks you meet.

 

Well, last night I did the vitally important step of a burn-in test, for the repaired 800XL... played Millipede and Star Raiders for about 5 hours, happy to report the burn-in test passed

[re-atari]

He couldn't remember where his 286 motherboard stash is, I got a big box of ISA cards... found 2 or 3 of them with 4464's (64Kx4 DRAMs), which aren't useful for the 800XL, but will come in handy someday when I upgrade the 600XL to 64K. Apparently that mod consists of 2 4464's and 3 jumpers, no extra logic chips or anything.

Might be worth while to keep nagging him to search through his stuff for those 286 mainboards Good news is, that, as you state, now that you already have the 4464's it just comes down to a bit of rewiring of the 600XL mainboard. Shouldn't take more than an hour.

 

I said they were 74LS158's, but I looked at them again after a good night's sleep... one's a 158, the others are a 74LS139 and a 74LS153. I found a 153 on one of those ISA boards, but not socketed. There are a couple of places left around town where I might be able to get 74xx series chips and possibly DRAMs, if I don't mind driving. Could order from Jameco/Digikey/etc too, but I'd rather drive for a couple hours than wait a week for delivery

Not sure about the LS153, but an LS139 is another standard type, so you should have no problem acquiring this one. Cost shouldn't be more than 1$.

 

Well, last night I did the vitally important step of a burn-in test, for the repaired 800XL... played Millipede and Star Raiders for about 5 hours, happy to report the burn-in test passed

There is a memory test program available, that is said to be very thorough. I remember a reply in a thread in this forum linking to this program during the last week or so. Can't remember the name and thread, though (I must be getting old)

But if your efforts leave a good feeling of accomplishment behind, that's the most important burn-in test succesfully passed! I call it the 'YES!'-factor. I had the same feeling a couple of years ago, when I managed to resurrect an iPAQ that wouldn't boot beyond the red-white startup screen. Somehow the firmware had gotten corrupted, needing a reflash to get back to working order. It has been doing so ever since

 

re-atari

[re-atari]

There is a memory test program available, that is said to be very thorough. I remember a reply in a thread in this forum linking to this program during the last week or so. Can't remember the name and thread, though (I must be getting old)

Searched a bit further, turned out the reply I was referring to was already a bit older than I had anticipated (even more proof that I must be getting old). The thread is at http://www.atariage.com/forums/index.php?showtopic=106664

 

re-atari

[Urchlay]

Found a place local to me (well, within 50 miles) that has all the 74LSxxx chips I need for under $1/ea. Probably drive out there pretty soon. They also have 41256's and 4164's for $3/each... someone's sending me a few 41256's though, if I can be patient I can save the $3

 

Dumb question: if I buy a modern 74LS158, it won't be a 3.3V chip or something? I mean I know there have been chip series where similar model numbers exist in TTL/NMOS/CMOS/etc varieties, and I know there are 5V, 3.3V, and probably other voltages used for logic circuits...

[Rybags]

Could be - but if it's DIP package it would likely be 5V, or maybe even capable of operating on varied voltages.

 

These days, common ICs often come in 2 or 3 formats (DIP, surface mount, PLC etc).

[+kheller2]

Yeah.. be patient. Care package is coming + some spare Atari LSI chips. I could use some 4464s for a 600xl though.. =)

Edited June 6, 2007 by kheller2

[Urchlay]

Yeah.. be patient. Care package is coming + some spare Atari LSI chips. I could use some 4464s for a 600xl though.. =)

 

Many thanks.

 

I've got 8 4464s in sockets on one ISA video card, and 8 more soldered to another, some of which I might blow up trying to desolder them (or not, I'm getting better at it). Need 2 per 600XL... how many 600XLs have you got?

[Urchlay]

Could be - but if it's DIP package it would likely be 5V, or maybe even capable of operating on varied voltages.

 

These days, common ICs often come in 2 or 3 formats (DIP, surface mount, PLC etc).

 

Ugh, I forgot to ask whether their 74LSxxx's are DIPs or what. I did tell 'em it was for a 25 year old computer, hopefully a parts store employee would know they'd need to be DIPs, but you never know.

[re-atari]

Found a place local to me (well, within 50 miles) that has all the 74LSxxx chips I need for under $1/ea. Probably drive out there pretty soon. They also have 41256's and 4164's for $3/each... someone's sending me a few 41256's though, if I can be patient I can save the $3

I know distance is relative, but I wouldn't call 50 miles local. If you drove for 50 miles in my country you would have crossed it halfway through

 

Dumb question: if I buy a modern 74LS158, it won't be a 3.3V chip or something? I mean I know there have been chip series where similar model numbers exist in TTL/NMOS/CMOS/etc varieties, and I know there are 5V, 3.3V, and probably other voltages used for logic circuits...

I read an article in an electronics mag at the library some time ago, that stated TTL's in 3.3V form are on the market, but their typenr. contains 'LV' to indicate this is a low voltage part. A 74LS158 would then be stamped a 74LV158. I faintly remember the article said these LV TTL's are only available in SMD, not DIP. I'd say you're on the safe side when you buy a standard LS in DIP. Can't hurt to check with the shop staff to make sure it's the right type, though.

Check this page http://www.interfacebus.com/voltage_LV_threshold.html and http://de.wikipedia.org/wiki/Transistor-Transistor-Logik for some background info. The Wiki page is also available in English, although the info there is not the same.

 

re-atari