Help identifying mod in Atari 800XLF

[santac89]

Hi everyone,

 

I just came back to my parents house to spend holidays and remembered an old 800XL I saved from the trash bin years ago but never managed nor tried to make it work or test it, so I decided it would be a good idea to try and repair it as a holiday project.

 

I found out it actually seems to be an 800XLF (PAL N version made in Taiwan) and it seems someone did some modification on it but I'm unable to identify why. The computer does powerup when pluggin 5v on it (partially, only the red light but no signal at all)

 

As you can see in the picture, someone removed R72, Q9, Y2 and jumpered a wire from Q9 to pin 28 (I believe it is called OSC). 

 

(U19 was removed by me since it was blown, and unfortunately the 6502 is also blown I guess, I'm hoping is only a crack of the ceramic due to a drop or something but I think it is more likely something blown from the inside, could this happen?)

 

Does someone has any knowledge of this kind of mod, if it is even one or it is just some kind of bypass/repair?

 

Thanks in advance!

 

 

 

 

 

Edited December 5, 2022 by santac89
Wrong extension for pictures

[TGB1718]

22 minutes ago, santac89 said:

blown from the inside, could this happen?)

Usually caused by BIG overheat inside, maybe caused by incorrect power supply, might need to check all the chips

although none socketed

 

not sure about the mod tho.

[santac89]

Thanks for the reply. My plan is to replace the missing components and remove that mod. Check in vain that the CPU does not work and try to find a replacement for it. Probably will find more about it when that is done but I'm not sure if I will be able to find the replacement CPU anytime soon sadly

[Vyvyan B.]

PS let go perhaps? It would take a fair amount of voltage to pop a chip like that. Perhaps you'd be better off finding a replacement board with sockets and keeping that one for spares, if anything is still good on it...

[BillC]

1 minute ago, Vyvyan B. said:

PS let go perhaps? It would take a fair amount of voltage to pop a chip like that. Perhaps you'd be better off finding a replacement board with sockets and keeping that one for spares, if anything is still good on it...

Perhaps someone plugged in a C64 power supply, the Atari computers don't like 9VAC .

[BillC]

2 hours ago, santac89 said:

Thanks for the reply. My plan is to replace the missing components and remove that mod. Check in vain that the CPU does not work and try to find a replacement for it. Probably will find more about it when that is done but I'm not sure if I will be able to find the replacement CPU anytime soon sadly

The 6502C SALLY CPU isn't that hard to find, below is an ebay listing from myatari(Bruce Carson of the former B&C Computervisons)

https://www.ebay.com/itm/143371502825?hash=item21619b84e9:g:vNcAAOSwM6thwnt8&amdata=enc%3AAQAHAAAAoPNQp3WLMyDzBrCUv32rgvF6zrO3jFjjB0jUJZEV09JfsVZfOeTjgMBH2LlnIuiM77IDBRzCIonvb7vQd1B5we7DtDAtugqbWC2giAGO9o0A8Rv2QUZYeq0C91WHPYf8Y4eqyQ4rsADC10X66jzu3XHxZwD%2FCHH33iDxz4vgsBT0WpAFA7jr1giHrMmGzr27wG9GYnWfHCrB3fJiFQgnnWo%3D|tkp%3ABk9SR6KU38GcYQ

Edited December 5, 2022 by BillC

[Beeblebrox]

@santac89 I assume you are based in the US?

 

As mentioned by others you may well find if a voltage surge is to blame then other components and ICs may well be damaged beyond repair. Another AA member undertook a fix of an A8 which had also been subjected to a C64 PSU and I seem to remember it was quite a job to fix).

 

Ideally you need another working 800XL or XE to test chips in. Pity this isn't a socketed board. Makes it so much harder. Also what you don't wanna do is source a new CPU, remove the old and socket it - and pop the new one in only for the board to damage it on powering it up.

 

Any chance of posting up full hi res images of both the top and underside of your board? Do you have MT branded ram chips? They often go as well and have a bad reputation.

 

As such with the likelihood of more components and ICs to diagnose and replace it might be harder to fix than first thought. Fact it is an XLF may make it harder also as far more documentation and discussion on stock 800XLs than XLFs. I've fixed one before, last year. (Although to be fair it's still essentially the same ICs, etc more or less - just rearranged and with the addition of the Freddie chip and minus a delay line IRRC).

 

I am wondering - aside from the damage - whether someone had attempted to convert it to NTSC at some stage that was started? (PAL GTIA and ANTIC chips are still in place). The PAL colour burst crystal is missing and the other missing components which you have not removed yourself are presumably part of the video circuit. Again if this was a stock 800XL it might be more obvious whether this was an attempted conversion. Not sure about the pin 28 wire to the transistor though.

 

These 800XLF PCB hi-res shots of top and bottom may (or may not) help (albeit a CA025926-001 4/84 Rev R1 board):

 

   

Edited December 5, 2022 by Beeblebrox

[santac89]

15 hours ago, Beeblebrox said:

I am wondering - aside from the damage - whether someone had attempted to convert it to NTSC at some stage that was started? (PAL GTIA and ANTIC chips are still in place)

That was my first assumption also, that someone tried to convert to NTSC. 

 

15 hours ago, Beeblebrox said:

Any chance of posting up full hi res images of both the top and underside of your board? Do you have MT branded ram chips? They often go as well and have a bad reputation.

 

Sure, I will try this week since I'm not at home until Friday. But I think I remember they were MT except for the first one in the columnt hat seems to have been replaced for another one.

 

15 hours ago, Beeblebrox said:

I assume you are based in the US?

No, sadly I'm in Germany and is not that easy to find Sallys there, I would need to import and pay the taxes. (Actually, I'm currently in Argentina visiting family. When I moved to Germany I left this board behind and now I'm trying to fix it while I'm here but I will take it over to Germany)

[Beeblebrox]

@santac89  You should be able to source a CPU fairly easily. You can get one for less than £15 from Ebay in the UK and it shouldn't cost that much to ship to Germany - even with the 19% tax and shipping. Depends on how much you are willing to invest in it - both financially and of your time.

 

https://www.ebay.co.uk/itm/154277718286

 

TBH it's a tricky one as actually if as I suspect at least a few more ICs will likely need replacing it may be worth sourcing another non working XE/XE for parts if you really still want the challenge of fixing this. At this stage it's really hard to tell.

 

You may well be looking at replacing the ram and CPU along with the missing passive components as a minimum. You'll also be able to get a colour burst crystal from a broken Atari 2600. 

 

Depends how much desire you have to fix this and just how far gone it is. The motivation would be there for me if I had it to fix it as it is an XLF. Plus I love a challenge. I've owned two amongst all the 800XLs I've come across.

 

Also bear in mind you'll be ideally paying for sockets as well.

 

As and when you have a moment do upload those top and bottom hi res images of your board. The AA community can assess things to a degree visually and there is a collective of great knowledge and advice here.

 

 

Edited December 6, 2022 by Beeblebrox

[Vyvyan B.]

This board is a "Pandora's box". Find a parts unit or replacement board and go from there.

[Vyvyan B.]

Here's a working unit for parts in Germany for $100. You'll spend months (and multiple times that) swapping parts around on this board. It's not worth the aggravation.

 

https://www.ebay.co.uk/itm/266003605845

Edited December 6, 2022 by Vyvyan B.

[Mclaneinc]

Yep, sounds like a load of aggravation, me, I'd just look for a cheap 800XL, I know it's a semi rare (?) model that you have but I'd get the XL and then try and fix the XLF as and when..

[santac89]

Thanks for all the replies. I think my best option is to buy a working unit for parts plus I could use the case since mine is really deteriorated. I will try to publish the hi-res photos as soon as possible and keep the post updated.

 

I didn't even know it was a semi-rare model. I saved it like 10 years ago from a basement but at that time I didn't even know where to start repairing it.

 

I was wondering if the mod was a PAL -> NTSC one as someone mentioned but it sounds rare since in Argentina the normative was PAL, so one less reason to think that someone wanted to do that mod.

[Beeblebrox]

TBH the appeal of it being an XLF and "rare" is neither here nor there really. Not super rare but if you love A8's and like fixing stuff then the buzz you get will motivate/reward you (hopefully). If not, save yourself some pain and potential frustration and just buy another 800XL you know works and keep this XLF for spares instead.

 

Entirely up to you are the end of the day.

 

Case in point I spent 5 days last year working on a dead to the world 130XE I had when I was in my teens and almost threw it under a bus (and myself) several times. Finally had a breakthrough and it now works. That's happened a fair few times over the last two years of me fixing various A8s up.

 

Last week in fact I couldn't work out why a new VBXE install in a working 800XL saw a virtually dead machine. Spent two days triple checking and also swapping out chips. Then I realised one tiny solder point I'd made was touching a nearby solder point (half a mm or so) and it was shorting the connection to the MMU. Soon as I sorted it the machine booted. It was almost imperceptable!!).

 

Generally XLs are pretty well built and hardy PCBs.  Less likely when removing chips that traces/tracks/via will lift (you really don't want that). XEs are terrible for that.

 

FYI if you are going for another 800XL for one with a label that says made in Hong Kong. It will be fully socketed. Some Taiwanese made 800XL's have some of the 40pin Ics socketed but most aren't socketed at all. Ready socketed 800XLS are GOOOOOD!

Edited December 6, 2022 by Beeblebrox

[Vyvyan B.]

This board looks like it got fried, overvolted, surge, or whatever it was that popped that CPU. You'd have to pull everything out of it, test it all, socket the entire board and replace anything that's been damaged before even attempting to put it back together. The cost of the parts alone would be more than it's worth. Pull the chips for spares (some of which are very likely to be bad too) and set it aside.

Edited December 6, 2022 by Vyvyan B.

[santac89]

24 minutes ago, Beeblebrox said:

like fixing stuff then the buzz you get will motivate/reward you

 

Totally, last year I spent weeks on 2 Atari Lynx II. In the end I did need to get some CPU and PPU replacement (aside from the usual power circuit being completely blown), but the joy after seeing it come to life is unique  I will definitely try to save this one for a while just for fun

[Beeblebrox]

Cool. Was hoping you'd say that being a fellow tinkerer!! The A8s in my collection I've worked most on have a special place for me. 

 

I've got some bargains on ebay at times so play the waiting game and I'm sure you'll get another 800XL.

 

In the meantime do yourself a fav and do as much reading on AA as you can. 100s of threads and advice on fixing these, especially the 800XL. Also check out flashjazzcat's videos. He's fixed a hell of a lot of A8s. 

 

Drop those hi res images as and when.

[santac89]

As promised. The pictures. Also, good news. I managed to get a completely working one with an XC12 cassette player really cheap here in Argentina. And it was manufactured here which is really cool to me. I didn't know these machines were also fabricated in South America. Completely socketed and all 😁.

 

I ordered in Germany a Sally replacement btw. So I will keep trying with the fried one once I'm back there.

[Beeblebrox]

Great news soiurcing a socketed XL.

 

So I just spent a couple of mins overlookin the pics of this XLF's board. Underside looks ok from first glance.

 

Top side:

 

Obvious damage to CPU and missing components aside, I did notice a resistor bottom left above the oscillator appears to be bridging it's original position and the right side of R35 which looks like an obvious change, (I'd had this on own XLF looking at old pics of it, but slightly differently).

 

Your XLF:

 

Mine (when I owned it):

 

Mine has the resistor piggy backing the R35 fully instead. It may well make no difference as both could be grounding to the PCB on the left of the added resistor in each case, but just thought I'd highlight the difference.

 

Also with your board I'd check continuity with all the contact points in and around the missing components to make sure they are all good, before adding parts back.

 

Might wanna check the 4050 (U28) also as lower leg pins look a little discoloured. (May just be the camera).

 

BTW if you want to avoid having to remove and socket all those MT ram chips and potentially damage the traces/vias in the process, you can source this 64K Sram plugin from Lotharek in Poland which is a quick alternative and is good value (and you'd have to buy new ram chips anyway if you were replacing the MT ram chips):

 

https://lotharek.pl/productdetail.php?id=291

 

Goes under the CPU and all that is needed is removal of the little caps next to each of the RAM chips to disable them.

 

FYI this is an old pic of my XLF board when I had it for comparrison:

 

Edited December 9, 2022 by Beeblebrox

[_The Doctor__]

looks like the video might have been modified for one of those south of the US border mixed video modes. I wonder where the complete list is these days?

[Beeblebrox]

7 minutes ago, _The Doctor__ said:

looks like the video might have been modified for one of those south of the US border mixed video modes. I wonder where the complete list is these days?

Interesting. Would there have been a manual switching over in such a mod?

[_The Doctor__]

not in my experience, they normally just convert to whatever system and leave it at that, not easily switchable.

[ijor]

21 hours ago, santac89 said:

As promised. The pictures. Also, good news. I managed to get a completely working one with an XC12 cassette player really cheap here in Argentina. And it was manufactured here which is really cool to me. I didn't know these machines were also fabricated in South America. Completely socketed and al

No Atari computer was manufactured in South America. The only parts that were manufactured locally were the (fake) label and sometimes also the PSU.

Edited December 9, 2022 by ijor

[+kheller2]

Is that a different oscillator/crystal speed and what is with the capacitor on it?

[santac89]

On 12/10/2022 at 12:06 AM, kheller2 said:

Is that a different oscillator/crystal speed and what is with the capacitor on it?

No idea about the crystal, but the cap says 10p on it so I guess it is a 10pF cap?

 

On 12/9/2022 at 11:24 AM, _The Doctor__ said:

looks like the video might have been modified for one of those south of the US border mixed video modes. I wonder where the complete list is these days?

Yes from what I've seen, it seems that it has been converted to PAL-N (at least it is what the label says).

 

 

@Beeblebrox thanks for the info and pictures. So far I noticed that when turned on, the gnd and positive event from the power input seems to be shorted, I'm trying to track down what could be the cause. I'm not entirely sure about this since when connected to the power, the red led comes on, so I'm not sure if I'm reading my multimeter incorrectly or if there is a short for real somewhere and the led is not affected by it. So far, I've removed the CPU to see if that was the cause but same results.

 

btw, the socketed XL that I managed to get seems to be in excellent status. I've ran the self-test and ALL green.

Edited December 11, 2022 by santac89