800xl with purple and green wires

[MrFSL]

Hello everyone!

 

I have acquired 3 800xl computers. (And I remember my original form the early 80s.) Only one of these has a purple and green wire soldered on the side:

 

Searching the Internets it appears that there are others with the same (including same color) wires.

 

 

Can anyone tell me the purpose or history of what/why this is? --- Just curious. This Atari of mine has some quirks that the others do not; and while I do not think it is related to these, it peaked my curiosity.

 

Thanks.

 

 

[erichenneke]

i just bought an 800XL over the weekend that has the exact same wires.  Seems extremely common, but I'm not sure why.

 

 

[TGB1718]

Would likely be a problem with the fabrication of the board or an omission so instead

of binning all the faulty boards, the wires were a fix.

 

May even have been there to improve some circuit stability.

 

It's quite a common thing for manufacturers to do.

[reifsnyderb]

My 800XL has the same wires.  These system boards are two layers only.  My belief is that Atari engineers were unable to add those two extra traces to the board and had to use the wires instead.  In that part of the system board there are lots of traces and it's a rather complicated section.

 

[_The Doctor__]

They are factory if that's the concern

[MrFSL]

4 minutes ago, reifsnyderb said:

My 800XL has the same wires.  These system boards are two layers only.  My belief is that Atari engineers were unable to add those two extra traces to the board and had to use the wires instead.  In that part of the system board there are lots of traces and it's a rather complicated section.

 

In my know-nothing-about-electronics observations I can't see any other differences between my 3 ataris. Even the ones that don't have the wires there are marked soldering points where the wires could go same as the one with wires.

 

37 minutes ago, TGB1718 said:

May even have been there to improve some circuit stability.

That sounds interesting.

[reifsnyderb]

I just looked at those pictures some more.  The one board is a Rev A. Board.  The other pictures don't show the board revisions.  My 800XL has a Rev C board....and has those wires.  My KiCad schematic of the 800XL has a Rev D Board and no wires.  Without tearing my 800XL apart, but by looking at the KiCad schematic, it appears both of those wires are most likely +5VDC.  The pictures show one of those wires going to the +5VDC pins of the 4051's.  So that would make sense.  Without looking at the back side of the boards in the pictures, the other wire (the one that goes to the trace under the resistors to the right of the PIA chip) looks like it may also be +5VDC as +5VDC is the only lines available nearby at both ends of a Rev D board.  Maybe those wires are there to improve stability??

 

Either way, they are factory.

 

 

[+CharlieChaplin]

The wires were factory made, think they forgot something... 

You can see it here: (XL pcb without / with wires)

 

Note: The wires at the OS-ROM, MMU and PBI are for extensions.

 

 

[MrFSL]

Thank you everyone for your replies. I figure they are factory as so many I see are color coded the exact same way. I suspect, given the gauge that it might be power more than signal. --- After asking this question I started researching and that is when I found out there were multiple revisions of the board.

 

What it comes down to is I have an Antonia board and it does not function correctly in this Atari. The other computers it does. Other than this one board everything else works in this Atari --- every other add on, etc. There are million reasons why that might be but for the untrained observer the only visual difference are these wires. I suspect that this particular Atari probably is suffering from some other hard to detect problem. --- but it peaked my curiosity as to why they were added.

 

Anyone have an Anotonia working in a 800xl with these wires (or not working for that matter?)

[Meadow Glen]

My 800xl with Antonia has the wires, in the same location.  They are both yellow.  The machine works with the Antonia, afaik, but unlike my other Atari's won't work with m side3.  Won't even start if the side 3 is plugged in.  I tried changing the 74ls08 to 74f08, no difference.  Anyway, for me the machine seems to work fine with Antonia, but just happens to be my only Atari that won't work with the side3 cart.   Just a mystery.  Do you happen to use a side3?  I"ve been wondering if antonia users use side 3 - just be nice to confirm it's compatible.

[_The Doctor__]

power is SIDEB's friend as is a good PIA chip with that F08

a good 5.2 volts and a nice F08 or better with a decent PIA as well as a great CPU chip clears up just about any SIDE B issues...

I use decent HCT's if an F08 doesn't cut it.

Edited April 20, 2022 by _The Doctor__

[Meadow Glen]

9 hours ago, _The Doctor__ said:

power is SIDEB's friend as is a good PIA chip with that F08

a good 5.2 volts and a nice F08 or better with a decent PIA as well as a great CPU chip clears up just about any SIDE B issues...

I use decent HCT's if an F08 doesn't cut it.

ah thanks, I give it a try..the power and the pia, tip, I'll see how that impacts it.  of course on the cpu...well if cpu swap doesn't fix it, then that would eliminate the antonia as any concern, so that would be interesting.  But if it did fix it, I'd still be wondering if my antonia or generally an antonia issue.  But anyway, sounds like I need to start eliminating variables, I'll try power, pia, then cpu, and see where I'm at.  thread hi-jack over   thanks

[MrFSL]

12 hours ago, Meadow Glen said:

My 800xl with Antonia has the wires, in the same location.  They are both yellow.  The machine works with the Antonia, afaik, but unlike my other Atari's won't work with m side3.  Won't even start if the side 3 is plugged in.  I tried changing the 74ls08 to 74f08, no difference.  Anyway, for me the machine seems to work fine with Antonia, but just happens to be my only Atari that won't work with the side3 cart.   Just a mystery.  Do you happen to use a side3?  I"ve been wondering if antonia users use side 3 - just be nice to confirm it's compatible.

Well now this causes me to wonder... 

 

I do not use SIDE3 --- but testing the Antonia I am always using "something" to load software be it IDE+, or AVG, or UnoCart, or Fujinet, etc. (I did not run it through all its paces this last time.)

 

The Atari with the wires ran all these other devices just fine without the Antonia and in virtually any combination. Also the system did boot with the Antonia and so you could say it seemed to work... but everything I tested the Antonia with came from one of these other devices. It just didn't work with these devices and so I blamed the Antonia.

 

Meanwhile my other Atari runs Antonia along with all these devices just fine so far (haven't yet tested IDE+.)

 

What you are describing --- about not running at all with the SIDE 3 I did see with the AVG I was using --- but really there are way too many variables at this point to draw any meaningful conclusions.

 

This is the first time I have ever heard about swapping out the 74ls08 for 74f08 --- I think I would like to try that and see if it makes any difference. Can anyone tell me if these parts are acceptable? 

 

https://www.digikey.com/en/products/detail/texas-instruments/SN74F08N/373669

 

 

10 hours ago, _The Doctor__ said:

power is SIDEB's friend as is a good PIA chip with that F08

For what its worth --- Running the Antonia requires less power than running the stock Atari.

 

I guess I could do a whole chip transplant from working machine to non-working machine... if someone really thought it was an IC related issue.

[_The Doctor__]

It just might be, I've seen CPU, PIA, LS chips, power/caps, and such mess with both of those devices. As to power issues, the supply and marginal Caps near the power in and power switch area. Not much else.

[MrFSL]

As always, thank you everyone for the answers. My original question "Can anyone tell me why these two wires are here" has been answered pretty well. As we understand it "they are there because Atari put them there" because, evidently, some of the boards required it. Somehow I hoped it was more dramatic a story... but there you have it.

 

The Antonia question is really secondary and I think there is a bunch of testing that even I can do with my modest (non-existent) skills.

 

2 hours ago, _The Doctor__ said:

It just might be, I've seen CPU, PIA, LS chips, power/caps, and such mess with both of those devices. As to power issues, the supply and marginal Caps near the power in and power switch area. Not much else.

 

I think when I have some spare time I could do a chip swap between two of the Atari's. I mean - with the Antonia I have already removed U4, U5, U9-U16, U26, U27, U29, MMU and 6502 --- (what is that? --- 15 chips?) there are not that many chips left to swap. If I can narrow it back to an IC I might start a better-titled thread and talk to Simius about my findings as well. --- If it is caps... well... that's beyond my skills and like I said --- EVERYTHING else works with this Atari so I doubt a re-cap to see if maybe it would help might be more than I want to do just to scratch an idle curiosity.

 

You all are great! Thanks again.

 

 

[_The Doctor__]

It would only be the couple electrolytic caps. I am not a fan of 're-capping' as a way of life, but sometimes it is needed.

As to chip swapping on the Atari... that's the norm these days, just keep an eye out for week sockets and debri, bad joints etc...

It sounds like you aren't keen to use a soldering iron on the machine, and after reading many a thread I can respect that. It'll get sorted eventually.

[reifsnyderb]

I can respect not liking to solder on you Atari, too.  My Atari 800XL is stock except for the chroma fix.  I only grudgingly removed two capacitors and added the resistor so I could connect it to a modern TV with a decent display.  I did keep the capacitors, though.

[MrFSL]

There are a lot of reason to not want to solder / de-solder... but you are correct; in my case its a lack of competence.

 

Also a difference between repairs and upgrades. I am really not keen on breaking out the soldering iron for upgrades.... as far as I can tell there aren't many times when its required. There are PBI, SOI, and CART solutions for just about any functionality you could want. --- For the Antonia board --- there is a signal missing from the PBI interface needed to get IDE+ working with the Antonia --- or you can get this signal via a jumper on the Antonia. That's the reason I can't test the IDE+ in this machine. --- But AVG works great and doesn't require this signal. 

 

For repairs... well... I would probably hire it out... but in this case, its not really "broken enough." We are talking about a modern day upgrade that doesn't work with an Atari that works with absolutely everything else I can throw at it.

 

Anyways its just my preference. For many people who have lots more Atari experience than I; opening an Atari and having wires run all over the place is what they have been doing to hack their Atari's since the beginning. To them I am the weird one!

 

[MrFSL]

On 4/21/2022 at 8:22 AM, _The Doctor__ said:

As to chip swapping on the Atari... that's the norm these days

A bit off topic... but since I started the topic I guess it doesn't matter....

 

@_The Doctor__   So -- for what its worth --- after careful inspection there is a good deal more different between these three Atari's of mine. Through the process of elimination I found that this 74LS08 chip:

 

When replaced with this one:

 

 

Made a HUGE difference. It actually made the Antonia usable. --- No other chip swaps seemed to have an effect.  --- In the end I don't think everything is working ---- but the Antonia at least can run software (XEX, CART, browse directories in SDX, etc.) --- none of this was capable until these were swapped.

 

All 3 Atari's are different and they all three seem to function a bit different with modern day peripherals. 

 

 

 

[+Stephen]

I believe that's the chip that is recommended to be swapped for a 74F08 in many machines.

[cwilbar]

16 hours ago, MrFSL said:

A bit off topic... but since I started the topic I guess it doesn't matter....

 

@_The Doctor__   So -- for what its worth --- after careful inspection there is a good deal more different between these three Atari's of mine. Through the process of elimination I found that this 74LS08 chip:

 

When replaced with this one:

 

 

Made a HUGE difference. It actually made the Antonia usable. --- No other chip swaps seemed to have an effect.  --- In the end I don't think everything is working ---- but the Antonia at least can run software (XEX, CART, browse directories in SDX, etc.) --- none of this was capable until these were swapped.

 

All 3 Atari's are different and they all three seem to function a bit different with modern day peripherals. 

 

 

 

 

I believe this is the chip that it is recommended to replace with a 74F08.  The reason why you see differences in behavior is the exact vendor implementation of the 74LS08 exhibits timing differences between the two LS08 chips.  The F08 switches faster.  Some newer upgrades are sensitive to timing and the F08 cures this.

 

 

[_The Doctor__]

yes, the 08's vary in timing and drive, this is exactly what I was expecting. Not all F08's are the same either, but are normally close enough to get the job done.

[MrFSL]

10 hours ago, _The Doctor__ said:

Not all F08's are the same either

Well the ones I linked above are on their way. The good news is that I have a computer that will work better with a better chip... ergo... I should be able to tell if its an improvement.

 

Thanks everyone.

[MrFSL]

I purchased this:

 

https://www.digikey.com/en/products/detail/texas-instruments/SN74F08N/373669

 

and replaced:

On 4/27/2022 at 5:36 PM, cwilbar said:

 

And now the Antonia works great in my 800XL with the odd wires.  

 

[BillC]

On 4/26/2022 at 10:02 PM, MrFSL said:

A bit off topic... but since I started the topic I guess it doesn't matter....

 

@_The Doctor__   So -- for what its worth --- after careful inspection there is a good deal more different between these three Atari's of mine. Through the process of elimination I found that this 74LS08 chip:

 

From the markings on the chip it appears to me to be a remarked counterfeit, they don't look like the markings on the other chips.