Sick 800XL, help?

[Urchlay]

For the past few weeks I've been trying to fix my poor dead 800XL that died a long time ago...

 

It was a 256K upgraded 800XL that got blown up by me using a variable power supply... someone turned the voltage up to 12V and I didn't notice. Powered it on, it didn't boot within 2-3 seconds, powered it off. It's never worked since then (black screen).

 

Just recently got a working 800XL, so I've been doing the part-swap thing. Discovered the dead 800XL had one bad RAM chip, a bad OS ROM, and bad PIA and GTIA. Replaced them all with parts from the good 800XL or a 600XL I've been using as a parts donor (except the 256Kx1 RAM, which someone was kind enough to send me... thanks kheller2!), but no joy: now I get a green screen instead of black, but it's still dead.

 

The dead 800XL only had sockets for some of the chips, so I've been desoldering them and trying them in the good 800XL (which is fully socketed). I've just finished testing every chip on the dead board except the two keyboard muxes (CD4051, which won't keep the thing from booting if they're bad). As I desolder each chip, I replace it with a socket... all the chips I desoldered except the ones mentioned above, are good: the other 800XL will boot fine with them.

 

I did remove the RAM upgrade board from the dead machine... the resistor above the RAM chips (R32) had been removed, so I replaced it (original part was a 3K, I don't have a 3K so I replaced with a 4.7K, which I was told would be OK). 4 of the pins on the PIA were bent up and connected to the upgrade board; I had to replace the PIA anyway, so they're all in the socket now. The board also plugs into a socket (U26) that normally has a 74LS158; unplugged it and replaced with a known-good 74LS158. Those were the only connections to the RAM upgrade board... so unless I've missed something, I should be back to a standard 64K configuration.

 

I discovered that the working 800XL (never been upgraded) will boot just fine with 256Kx1 RAMs (though of course it only sees 64K of memory), so I know my 256Kx1 RAMs are OK...

 

I still have to finish socketing the dead board (removed and tested 9 chips this evening, including the MMU, all were good). Once I've done this, I'll try it one more time with all known-good parts... though I already know it won't work (I tried to boot it with all good parts last night, though I didn't know for sure they were all good yet).

 

The only other oddity I came up with: I checked the Vcc line at the RAM chips, which should be +5V. On the good 800XL it's exactly 5V according to my digital meter... on the dead board, it's 4.87 volts (using the same external power supply). I don't know whether this is normal... should I be suspecting some bad discrete part(s) in the power section? If I had 8 or 10 working 800XLs to test, I could answer this question myself (if all of them read 5V exactly, I'd know the 4.87V is definitely a problem).

 

What else should I be looking for? Bad circuit traces? During the 15+ years since I blew it up, I didn't always store the dead 800XL in the best places (attic, basement, trunk of my car for a while).

 

I may try to use the upgrade board and 256Kx1 RAMs to upgrade the working 800XL to 256K (at least one of the 3 chips on the board is good; I have no way to test the other 2, since they're not parts that are used in a stock 800XL), but that won't help me fix the dead one...

 

Is there something I'm missing? I'm no hardware expert, though I've almost perfected my desoldering technique by now... I'll start checking traces with the ohmmeter, I've got the schematic and a good board to compare with. If anyone can think of anything else, please help... I'm confused

[re-atari]

It was a 256K upgraded 800XL that got blown up by me using a variable power supply... someone turned the voltage up to 12V and I didn't notice. Powered it on, it didn't boot within 2-3 seconds, powered it off. It's never worked since then (black screen).

 

Just recently got a working 800XL, so I've been doing the part-swap thing. Discovered the dead 800XL had one bad RAM chip, a bad OS ROM, and bad PIA and GTIA. Replaced them all with parts from the good 800XL or a 600XL I've been using as a parts donor (except the 256Kx1 RAM, which someone was kind enough to send me... thanks kheller2!), but no joy: now I get a green screen instead of black, but it's still dead.

 

The dead 800XL only had sockets for some of the chips, so I've been desoldering them and trying them in the good 800XL (which is fully socketed). I've just finished testing every chip on the dead board except the two keyboard muxes (CD4051, which won't keep the thing from booting if they're bad). As I desolder each chip, I replace it with a socket... all the chips I desoldered except the ones mentioned above, are good: the other 800XL will boot fine with them.

 

The only other oddity I came up with: I checked the Vcc line at the RAM chips, which should be +5V. On the good 800XL it's exactly 5V according to my digital meter... on the dead board, it's 4.87 volts (using the same external power supply). I don't know whether this is normal... should I be suspecting some bad discrete part(s) in the power section? If I had 8 or 10 working 800XLs to test, I could answer this question myself (if all of them read 5V exactly, I'd know the 4.87V is definitely a problem).

 

What else should I be looking for? Bad circuit traces? During the 15+ years since I blew it up, I didn't always store the dead 800XL in the best places (attic, basement, trunk of my car for a while).

 

Is there something I'm missing? I'm no hardware expert, though I've almost perfected my desoldering technique by now... I'll start checking traces with the ohmmeter, I've got the schematic and a good board to compare with. If anyone can think of anything else, please help... I'm confused

Are you really sure you want to check the traces of the mainboard, it will be very timeconsuming. And you have to check the throughplated holes, as well. I usually do a visual check with a magnifying glass and a strong light source underneath the board, this will point out 99% of any broken traces.

If the board checks out OK, I'd start by verifying if VCC is present on the rest of the IC's as well. If you check the schematic, you'll see that on the A8's mainboard the 5V from the Din jack gets divided into 3 main VCC planes. Each one of these planes provides power to a different part of the computer. The planes are all seperately decoupled and filtered by capacitors and coils. This is done to prevent one part, say the DRAM refresh circuitry, from inputting distorting 'noises' into other parts, like the audio amplifier circuitry. The fault you are experiencing might have to do with a burnt coil, so check if either side of L1, L2 and L3 has 5V present. Measure the coils and ferrite beads on the mainboard with the A8 switched off as well, you should measure a few ohms through them. Since you get around 5V on the DRAM's, L1 and the digital plane (delivering VCC to the digital IC's like CPU, Antic, both roms, etc.) appear to be OK. Using the schematic you can easily check out the other planes.

It's quite possible that the fault with your A8 is caused by a transistor or diode that was burned out by the overvoltage as well. You wrote both PIA and GTIA were bad, so it might be a good idea to check the transistors in the circuitry surrounding these two. A number of them are more or less directly wired to VCC. You could replace them with new ones all the same, you' d have to desolder them to properly test anyway (incircuit testing almost always leads to false results). And there's only a few of them on the mainboard.

I think you're right that the 4051's most likely are not the culprits. It's just a thought, but the RF modulator is connected to VCC as well. You can check if something inside this has shorted, by temporarily disconnecting it from VCC (remove pin 2). Well, that is, if you're not using RF to get an image on your TV...

Chances are the electrolytic capacitors on your mainboard will have taken the overvoltage without a problem. In my A8 they are all rated at 16V, so will easily sustain 12V. It can't hurt to check the rating of yours, maybe Atari put in caps rated at 10V. The caps could have dried out after all these years, so replacing them probably is not a bad idea.

Resistors hardly ever fail, and if they do, you'd be able to see it clearly. I have seen resistors that appeared totally burnt, yet still had retained their nominal value (according to the schematic of course, the color coded rings weren't visible anymore )

 

I'm curious to find out what the fault is with this board, so keep us posted!

 

re-atari

[Urchlay]

Since you get around 5V on the DRAM's, L1 and the digital plane (delivering VCC to the digital IC's like CPU, Antic, both roms, etc.) appear to be OK. Using the schematic you can easily check out the other planes.

They all look good... +5V at the points marked 5A 5B 5C 5D on the schematic (at the coils). Also, +5V is present on the Vcc pin of every IC.

It's quite possible that the fault with your A8 is caused by a transistor or diode that was burned out by the overvoltage as well. You wrote both PIA and GTIA were bad, so it might be a good idea to check the transistors in the circuitry surrounding these two. A number of them are more or less directly wired to VCC. You could replace them with new ones all the same, you' d have to desolder them to properly test anyway (incircuit testing almost always leads to false results). And there's only a few of them on the mainboard.

The transistors look to be all NPN (except inside the modulator, which I don't care about, and will remove if it has problems)... the schematic doesn't give a part number. Will 2N2222's work?

It's just a thought, but the RF modulator is connected to VCC as well. You can check if something inside this has shorted, by temporarily disconnecting it from VCC (remove pin 2). Well, that is, if you're not using RF to get an image on your TV...

If I get this board working, I probably will remove the RFM and channel switch, to make room for a set of standard jacks (RCA for audio/composite, and S-video). The case is in terrible shape, so I don't mind making holes in it for these.

Chances are the electrolytic capacitors on your mainboard will have taken the overvoltage without a problem. In my A8 they are all rated at 16V, so will easily sustain 12V. It can't hurt to check the rating of yours, maybe Atari put in caps rated at 10V. The caps could have dried out after all these years, so replacing them probably is not a bad idea.

The caps look like they're mostly rated for 16V. None of them are leaking electrolyte or have that bloated "about to pop" look, but that doesn't necessarily mean they're good, either... am assuming the ones in the power section are OK, or I wouldn't get 5V...?

Resistors hardly ever fail, and if they do, you'd be able to see it clearly. I have seen resistors that appeared totally burnt, yet still had retained their nominal value (according to the schematic of course, the color coded rings weren't visible anymore )

I've seen that, in an old TV. Made me scratch my head for a minute...

I'm curious to find out what the fault is with this board, so keep us posted!

I'm curious too

 

I don't have an oscilloscope, but I do have access to one (have to drive 15-20 min). I'm not really a scope expert, but are there any simple tests I can do? I assume I should get a 1.79MHz (or multiple) signal from one or the other pin of the clock crystal, but beyond that I don't know what to look for in a digital circuit... if this were a stereo, I might have a clue

 

I want to at least trace the address/data lines from the ROMs to the data bus... they are the only "big" ICs I desoldered (since ANTIC/POKEY/6502/GTIA/PIA were already socketed). There's always a chance that I added a new problem when I desoldered and socketed all those chips (my soldering is getting better with practice, but nobody's perfect). Also, need to find out which of the small logic chip(s) have direct connections to the PIA, OS ROM, and RAM, and trace those... since those 3 chips were bad.

 

Am not 100% sure what's going on with the GTIA. If I put it in the good 800XL, it boots to the self-test menu, with "audio-visual" pre-selected... but if it were fried, I shouldn't get a display at all, right? It may be that the GTIA is fine, but is the wrong revision for the new motherboard, or something like that...? Regardless, I replaced it with a known-good part from a 600XL, and don't have to worry about it right now.

 

Something interesting: last night I swapped all the RAMs between the good and bad boards, on MetalGuy66's advice (previously, I had tested the RAMs on the bad board one at a time, by swapping each one into the same socket on the good board). The bad board still didn't boot, and neither did the good board (even though each of those RAMs tested fine, individually)! I was able to get the good board to boot by moving the RAMs around (same RAMs in different positions), but couldn't do the same with the bad board (not surprising, it has other problems). Not really sure what's going on there though.

[Rybags]

The master clock should be around 14 MHz. It's then divided by 8 for the systems clocks.

[re-atari]

The transistors look to be all NPN (except inside the modulator, which I don't care about, and will remove if it has problems)... the schematic doesn't give a part number. Will 2N2222's work?

Q1 to Q6 are 2N3904's, Q8 and Q9 are 2N3906's. They are standard NPN and PNP types, just like a BC547 and BC557, dirt cheap to buy. Q7 is an MPSA-55, which is used for the motor control of the cassette recorder.

Here is the schematic I used:

 

 

The caps look like they're mostly rated for 16V. None of them are leaking electrolyte or have that bloated "about to pop" look, but that doesn't necessarily mean they're good, either... am assuming the ones in the power section are OK, or I wouldn't get 5V...?

Like you say, a degraded cap can usually be identified visually. From your description, I'm inclined to doubt the board has a defective cap. If so, you would not have measured 5V at every IC.

 

I don't have an oscilloscope, but I do have access to one (have to drive 15-20 min). I'm not really a scope expert, but are there any simple tests I can do? I assume I should get a 1.79MHz (or multiple) signal from one or the other pin of the clock crystal, but beyond that I don't know what to look for in a digital circuit... if this were a stereo, I might have a clue

I'm afraid I don't have any experience on how to use a scope. But from what I've heared, crystal oscillators almost never fail.

I usually find audio equipment more troublesome to repair. With digital circuits it's simply a matter of go/no-go (oversimplified), but with analog circuits, especially high-end audio stuff, there's so much more aspects to take into account and everything can interfere with other part of the circuitry. For example, I have an ongoing repair project to get my Nakamichi 581 to have its left channel record and output at more than -20dB. Already did the usual suspects (replaced polypropyleen and mica caps with styroflex ones), but no luck yet.

 

I want to at least trace the address/data lines from the ROMs to the data bus... they are the only "big" ICs I desoldered (since ANTIC/POKEY/6502/GTIA/PIA were already socketed). There's always a chance that I added a new problem when I desoldered and socketed all those chips (my soldering is getting better with practice, but nobody's perfect). Also, need to find out which of the small logic chip(s) have direct connections to the PIA, OS ROM, and RAM, and trace those... since those 3 chips were bad.

That would be my first step before desoldering and testing the transistors.

 

Am not 100% sure what's going on with the GTIA. If I put it in the good 800XL, it boots to the self-test menu, with "audio-visual" pre-selected... but if it were fried, I shouldn't get a display at all, right? It may be that the GTIA is fine, but is the wrong revision for the new motherboard, or something like that...? Regardless, I replaced it with a known-good part from a 600XL, and don't have to worry about it right now.

I don't know if different rev's were used during production of the 800XL. I have succesfully swapped GTIA's from a 1984 'regular' 800XL and a later 800XLF(reddy), both machines worked. I do recall a story about a certain production run of the GTIA that contained a bug, but IIRC this batch was only built into 130XE's.

 

Something interesting: last night I swapped all the RAMs between the good and bad boards, on MetalGuy66's advice (previously, I had tested the RAMs on the bad board one at a time, by swapping each one into the same socket on the good board). The bad board still didn't boot, and neither did the good board (even though each of those RAMs tested fine, individually)! I was able to get the good board to boot by moving the RAMs around (same RAMs in different positions), but couldn't do the same with the bad board (not surprising, it has other problems). Not really sure what's going on there though.

It's probably timing delays that are causing this. The 74LS's that provide the address decoding circuitry all have their own timing delays. These delays differ between components of the same type and can even differ between manufacturers. Speaking about timing, did you already swap U29 (delay line)?

It looks like you finally managed to place the DRAM's in such an order that they could keep their contents (has to do with refresh access time). If they are too slow to keep up with the timing the A8 provides, their contents will get corrupt ('falling bits'), resulting in a system's lock-up. Well, hopefully; you really don't want a computer to just keep on running with a corrupted program or data in it's memory. Imagine doing your billing or bookkeeping on such a system

Now, as the lenght of the traces on the mainboard also provides a small timing delay, this has to be taken into account too. If you look closely, you will see that the traces that lead from the bank of resistors right above GTIA to the DRAM's are different in length, it's about 5-8 cm. The timing difference this causes may just be enough for one (or more) of your DRAM's to fail in this particular place. So, I'd mark up which DRAM worked OK in which spot in this A8 for future reference.

On this subject, if you look carefully, you will notice that on modern computerboards traces sometimes do not follow a straight path, but run through a strange labyrinth. This is done on purpose to make up for timing delays, making sure signals concurrently reach their point of destination at precisely the right time. On modern computerboards the use of 74F(ast) types has become more or less standard, unless timing is not an issue. They are a bit more expensive and harder to come by.

 

re-atari

[Urchlay]

Q1 to Q6 are 2N3904's, Q8 and Q9 are 2N3906's. They are standard NPN and PNP types, just like a BC547 and BC557, dirt cheap to buy. Q7 is an MPSA-55, which is used for the motor control of the cassette recorder.

Here is the schematic I used:

...

Ah! That schematic has the part numbers... I was using the schematic drawn by Jerzy Sobola, which is split into 12 pages and doesn't have the transistor part numbers (though it's pretty complete otherwise).

I'm afraid I don't have any experience on how to use a scope. But from what I've heared, crystal oscillators almost never fail.

I usually find audio equipment more troublesome to repair. With digital circuits it's simply a matter of go/no-go (oversimplified), but with analog circuits, especially high-end audio stuff, there's so much more aspects to take into account and everything can interfere with other part of the circuitry. For example, I have an ongoing repair project to get my Nakamichi 581 to have its left channel record and output at more than -20dB. Already did the usual suspects (replaced polypropyleen and mica caps with styroflex ones), but no luck yet.

I wouldn't want to touch really high-end audio stuff either... I've successfully fixed some cheap receivers, usually by finding which power transistor or cap is bad and replacing it. I mostly used a scope for visually comparing the left and right channel signals at the same point (which can be done with a speaker instead). Actually, this scope I have access to wouldn't be useful for Atari repairs anyway: it's too slow (rated in the kilohertz). It's an old Heathkit, late 1950s or early 1960s. Pretty impressive that someone built it from a kit though.

I want to at least trace the address/data lines from the ROMs to the data bus... they are the only "big" ICs I desoldered (since ANTIC/POKEY/6502/GTIA/PIA were already socketed). There's always a chance that I added a new problem when I desoldered and socketed all those chips (my soldering is getting better with practice, but nobody's perfect). Also, need to find out which of the small logic chip(s) have direct connections to the PIA, OS ROM, and RAM, and trace those... since those 3 chips were bad.

That would be my first step before desoldering and testing the transistors.

...and I think I may have found the culprit! There are two traces on the top of the board that look like they got damaged by being hit by something with a sharp corner. I haven't metered them yet, but one's visibly missing part of the trace, and the other looks like it might be. This must have happened while it was in the trunk of my old car: I put it in there along with a bunch of other junk when moving, and forgot it was there... so it stayed for almost a year. The screws weren't in the case, and at some point (due to braking/acceleration I guess) the top of the case came off.

 

Going to find out where these 2 traces go, add jumper wires. With any luck, that'll fix it... unless I messed something up desoldering/socketing all the ICs. Wish I'd seen the cracked traces first

 

Moral of the story: always put the screws back in when you're done working on stuff, even if you don't manage to fix it! Also, never keep anything in the trunk of your car... Also also, always check the simple stuff first! Actually, I would have had to desolder the OS ROM anyway: it really is bad.

I don't know if different rev's were used during production of the 800XL. I have succesfully swapped GTIA's from a 1984 'regular' 800XL and a later 800XLF(reddy), both machines worked. I do recall a story about a certain production run of the GTIA that contained a bug, but IIRC this batch was only built into 130XE's.

I've heard the buggy GTIA was only used in PAL XE's, and that the bug only manifested in the GTIA graphics modes (9 thru 11). Regardless, a buggy rev of the GTIA wouldn't cause the Atari to boot to the self-test: the affected XE's boot and run normally until you try to use one of the broken graphics modes.

I swapped all the RAMs between the good and bad boards ... I was able to get the good board to boot by moving the RAMs around (same RAMs in different positions), but couldn't do the same with the bad board

It's probably timing delays that are causing this. The 74LS's that provide the address decoding circuitry all have their own timing delays. These delays differ between components of the same type and can even differ between manufacturers. Speaking about timing, did you already swap U29 (delay line)?

Yep. I even socketed it (cut some pins off a socket to match the ones missing from the chip).

It looks like you finally managed to place the DRAM's in such an order that they could keep their contents (has to do with refresh access time). If they are too slow to keep up with the timing the A8 provides, their contents will get corrupt ('falling bits'), resulting in a system's lock-up. Well, hopefully; you really don't want a computer to just keep on running with a corrupted program or data in it's memory. Imagine doing your billing or bookkeeping on such a system

Now, as the lenght of the traces on the mainboard also provides a small timing delay, this has to be taken into account too. If you look closely, you will see that the traces that lead from the bank of resistors right above GTIA to the DRAM's are different in length, it's about 5-8 cm. The timing difference this causes may just be enough for one (or more) of your DRAM's to fail in this particular place. So, I'd mark up which DRAM worked OK in which spot in this A8 for future reference.

Ah! That makes sense. Annoying though... means that, even if I fix everything else on this board, it still might green-screen due to the placement of the RAM chips. When/if I get to that point, I'll swap the RAM back into the good board and keep track of its arrangement, see if it works that way, or else move them around till it works... then put the RAM back in the (hopefully) repaired board, and if it doesn't boot, start swapping the address decoders and other 74LS chips.

 

On the other hand, it may mean that the 256Kx1 RAM chip I thought was bad, isn't really bad at all. I decided it was bad after trying it in only one position on the good board (all the others worked that way). It may actually work fine if I shuffle them around some. Fortunately I didn't throw it out (just stuck a piece of red tape on it).

 

Even if I never get the board working, I'm learning a lot of cool and useful stuff... and I'll have a fighting chance of fixing the next "not sure if it works" 800XL I buy from ebay (wish people would be honest: if it doesn't work, say so!)

 

Now that I've found cracked traces, I'm pretty sure I can get this thing working.

[Urchlay]

...and I think I may have found the culprit! There are two traces on the top of the board that look like they got damaged by being hit by something with a sharp corner. I haven't metered them yet, but one's visibly missing part of the trace, and the other looks like it might be.

Nope, these 2 traces are actually fine. There's a scratch in the PCB on top of them, but the actual traces are intact.

 

Currently ohming out the traces on the chips I socketed... this could, uhhh, take a while. Technique is to measure from the top of the chip pin (with chip in socket) to wherever the trace goes according to the schematic and my eyeballs. Also checking adjacent pins, make sure they're not shorted (checking the good board if they are, to see if they're supposed to be. Pins 27-28 of the OS ROM are shorted together on the good board, thought I'd found something wrong for a second).

[+kheller2]

Do you get any sound with the green screen by pressing keys and does RESET work?

[Urchlay]

Do you get any sound with the green screen by pressing keys and does RESET work?

 

No idea, haven't tried it with the keyboard. Will check.

[Urchlay]

Nope, these 2 traces are actually fine. There's a scratch in the PCB on top of them, but the actual traces are intact.

 

No, they're *not* fine, either! They *look* OK, but one of 'em is definitely open.

[+kheller2]

Hmm talking to yourself is the first sign of mental illness. I wonder what posting to one's self is.

[Urchlay]

No, they're *not* fine, either! They *look* OK, but one of 'em is definitely open.

 

Success! It boots!

 

The broken trace leads from the D1 pin on the CPU to the D1 pin on the BASIC ROM (and from there to D1 on the OS ROM). The trace has 2 solder pads inline, one near the CPU and the other near the ROMs, I was able to solder the wire to both pads to get continuity around the broken part... It's odd, the trace looks complete if I hold it up to a light, but it definitely ain't.

 

Now I gotta make sure I'm getting a full 64K of RAM, test the keyboard, cart port, SIO... the keyboard is probably in bad need of cleaning/repair, but that'll be easy compared to what I did to the motherboard! Restoring the 256K RAM upgrade will be a snap, too (though I gotta decide which 800XL it should go in).

 

Deep gratitude to everyone who posted suggestions and sent me spare parts! *Many* thanks, guys!

[re-atari]

No, they're *not* fine, either! They *look* OK, but one of 'em is definitely open.

 

Success! It boots!

 

The broken trace leads from the D1 pin on the CPU to the D1 pin on the BASIC ROM (and from there to D1 on the OS ROM). The trace has 2 solder pads inline, one near the CPU and the other near the ROMs, I was able to solder the wire to both pads to get continuity around the broken part... It's odd, the trace looks complete if I hold it up to a light, but it definitely ain't.

 

Now I gotta make sure I'm getting a full 64K of RAM, test the keyboard, cart port, SIO... the keyboard is probably in bad need of cleaning/repair, but that'll be easy compared to what I did to the motherboard! Restoring the 256K RAM upgrade will be a snap, too (though I gotta decide which 800XL it should go in).

 

Deep gratitude to everyone who posted suggestions and sent me spare parts! *Many* thanks, guys!

Congrats, and well done! Looks like you experienced the 'YESSS' feeling when the A8 booted up. Another one rescued from the scrapheap

 

re-atari

[mimo]

[Urchlay]

Looks like you experienced the 'YESSS' feeling when the A8 booted up. Another one rescued from the scrapheap

 

Yep. Was worth all the effort.

 

I do wish I'd checked the traces *before* desoldering and socketing every single chip... but hey, now I have two fully-socketed 800XLs, and I don't suck at desoldering any more

[carmel_andrews]

I guess you used a number of read/write wires to connect the various chips together (to compensate/overcome the various broken MB traces)....speaking as a non tech head (me that is)

Edited June 28, 2007 by carmel_andrews

[+kheller2]

Urchlay, give us a picture!

[Urchlay]

I guess you used a number of read/write wires to connect the various chips together (to compensate/overcome the various broken MB traces)....speaking as a non tech head (me that is)

 

Yep, exactly that... actually I only had one broken trace, so only used one wire.

 

Urchlay, give us a picture!

 

Could do... but you have to promise not to laugh at my soldering

[Urchlay]

Urchlay, give us a picture!

 

Sorry guys, can't find my camera... one good thing about the old-school tech: it wasn't so miniaturized that you could lose it easily...

 

An informal poll:

 

Now I've got 2 working 800XLs... one in very nice condition, inside and outside, 100% stock... and the other (the one I just fixed), which looks like crap on the inside (RF shield is rusty, motherboard has dings in it). Both work just fine. I've got one 256K RAM board for an 800XL. Which machine would you put the upgrade in, if you were me?

[mimo]

which one has the nicest keyboard? put the upgrade in that one and use it

[Urchlay]

which one has the nicest keyboard? put the upgrade in that one and use it

 

They're both the mylar foil type keyboard, and they feel about the same. One of them has uneven keycaps (a few of them are slightly taller than the others), but it's hard to notice when you're looking at it, and I can't tell when I'm typing on it. Anyway, if one keyboard was better, swapping the keyboards wouldn't be a problem at this point...

 

Whichever one gets the 256K upgrade will probably also become my "modding practice" machine. I want to do a simple 4-in-1 OS mod (with hardware switches) and an internal SIO2PC at minimum. Trying to decide whether I should mod the almost-new, really pretty one, or the old one that looks like crap (and consequently won't bother me as much if I screw it up trying to mod it).

 

Both machines will probably get a supervideo or clearpic mod... I may do supervideo in one and clearpic in the other, just to be able to compare them. The "modding practice" machine will probably get a standard S-video jack and RCA jacks for composite and audio, instead of the proprietary Atari 5-pin DIN connector (which means cutting a hole in the case. Hm. Maybe I should use the beat-up machine for that).

 

Neither 800XL has a box or any of its original packaged stuff, and neither one cost me any money (the almost-new one was given to me recently, and the ugly one I've owned for almost 20 years).

 

Hm. The more I think about it, the more I think the ugly old one should be the modding machine.

[re-atari]

Hm. The more I think about it, the more I think the ugly old one should be the modding machine.

That would be my suggestion as well. Keep the pristine one in original state, use the ugly one for modding.

 

re-atari

[Urchlay]

Update:

 

My stock 800XL will stay stock, or perhaps get a single wire soldered to the board to give it chroma output.

 

The other 800XL is the one I'll stuff full of mods... I've reinstalled the 256K upgrade board. It works fine, wasn't fried.

 

Also I've done a Super Video 2.1 upgrade, which came out really nice... this is now the 2nd best video on any of my A8's (the best is still the stock beige 800 though).

 

The keyboard was full of some sort of clear, odorless, oily substance, about the consistency of lamp oil, but without the smell. It was inside the keyboard, between the mylar layers, but not on the keys, so whatever it was, it wasn't a spill (if this junk had got on the keys, it definitely would have left a residue). Someone told me it was probably the remnants of some sort of industrial lubricant or sealant used at the factory that broke down into goo over time (accelerated by the conditions in the trunk of my car). Yet another reason why you should *never* keep good stuff in your car or attic... the good news is, the gooey mess came right off with soapy water followed by q-tips and alcohol, and the keyboard works fine now.

 

Also to make the keyboard work, I had to cut a little more than 1/4" off the end of the mylar cable, where it plugs into the motherboard. Several traces were actually cracked... now it works, but no longer folds up exactly right when I close the case (can still close it up, just have to pay attention when doing it). If anything happens to this keyboard cable in the future, I can cut maybe 1/4" more off it, but it'll be almost impossible to reassemble the case without help, if I ever do that (someone would have to hold the top case half in the air while I plug in the keyboard, if the cable got any shorter).

 

Now that the keyboard works and I've got a super video upgrade and the 256K upgrade working, this 800XL is working better than it did when I first bought it (though it looked better, back then).

 

The cardboard insert that sits under the motherboard (between it and the bottom RF shield) was disgusting-looking, so I made a new one by tracing the old one on some cardboard and cutting out the holes with an X-acto knife. It came out better than I expected, except the one round hole is more oval-shaped than round (hard to cut in a perfect circle with a straight blade).

 

Also, I found my camera finally (it fell behind my big honkin' PC and got buried in a rats' nest of cables). I'm trying to take pictures, but I'm having trouble with lighting: if I use the flash, or bright room lighting, I get so much glare from the plastic case that you can't see much detail... and if I turn off the flash and dim the lights, the camera takes such a fuzzy grainy picture that you can't see anything at all. Still working on this (maybe I can take it outside and use the sun for a light source?)

[re-atari]

Also, I found my camera finally (it fell behind my big honkin' PC and got buried in a rats' nest of cables). I'm trying to take pictures, but I'm having trouble with lighting: if I use the flash, or bright room lighting, I get so much glare from the plastic case that you can't see much detail... and if I turn off the flash and dim the lights, the camera takes such a fuzzy grainy picture that you can't see anything at all. Still working on this (maybe I can take it outside and use the sun for a light source?)

An old photographers' trick is to put a piece of cloth, such as a handkerchief or a small piece of a bedsheet, over the flash. If the flash still turns out to be too strong, just fold the cloth in double and try again. Don't take a coloured cloth, though, as this will shift the colours in the photos. It will enhance itself and dim the complementary colour.

 

re-atari

Edited July 12, 2007 by re-atari