After hi res image of 800XLF CA025925-001 R3 (9-84) PCB WITHOUT components

[Beeblebrox]

I am currently working on an 800XLF which has a CA025925-001 Rev 3 (circa 9-84) PCB

 

I am looking to source hi resolution images of the topside, (and underside), of this board WITHOUT any components on it.

 

I managed to locate similar images of an earlier revison of the board of the same year, (4-84). I believe that was the Atari prototype and then in August 1984 they settled on a revision layout which became the 9-84 Rev 3 which I have.

 

So I am after a similar set of images to this cropped example, unpopulated:

 

I've managed to find images of my 9-84 pcb top and bottom but all with the components installed topside, which unfortunately doesn't help.

 

I am testing continuity of the traces on both side of the board for broken/damaged ones, and having a visual photo map of the top of the PCB without components would make my life so much easier for those obscured by the ICs and other passive componentry. I can follow the 4-84 rev PCB images I have to a degree but having attempted to do so it soon became apparent there are some distinct differences in the layout of the board's components, changes in the trace layouts, etc that meant it wasn't going to work.

 

I've had a good look in all the usual places including on AA, Atarimania and a good few hours Googling. I can find schematics and service guides, but schematics don't cover this particular revision board only other XLF PCB layouts it seems, and service manuals are just 800XL generic ones. Ideally I really need images like the above of my exact PCB which clearly show the traces and silkscreen. 

 

Failing sourcing the images a silkscreen schematic of the topside would also help to a degree but again finding one for this rev 3 XLF board has proved tricky.

 

FYI this is an image of a populated 9-84 rev 3 board like mine:

 

 

Thanks in advance 

Edited February 20, 2022 by Beeblebrox
incorrect info corrected

[+kheller2]

 I don’t think you will find a picture of the bare board.   I looked for several years when doing research on the 128K XLF.  There was a later Rev 4 board plot according to my notes but I’ve never seen one.  Rev 3 had Freddie power instability (filtering cap is not wired correct ) if I recall.  But it’s a good board and the monitor port is at least fully wired.  Good luck on the repair.  

[Beeblebrox]

@kheller2  Thanks - I think you are right in terms of the chances of finding these PCB images.

 

------------------

 

This fixer upper (PAL) 800XLF is proving a real challenge.

 

Current state of play is this:

 

Initially a non socketed 800XLF, with the exception of Freddie which was socketed with an old style double wipe socket - seemingly from the factory comparing the solder work with the rest of the PCB.

 

I've got to a stage after all the work done to date where it initially boots to the red screen, then after a second turns to black, and I get the two sound pops a second apart during this process. (I've read this is good in terms of RAM, CPU and ANTIC doing their thing).

 

After all the work already done to it I've recently swapped put and re-tested all the ICs in my working 65XE one at a time (with the exception of the 2 x 4051 MUX keyboard ICs which remain soldered to the board) - all ICs currently in place worked. (Early on when first starting the original PIA was bad, all MT RAM was replaced after 2 x bad chips found and a bad Os rom chip too).  I've also put multiple known to work ICs from my 65XE into the XLF one at a time to test - just in case.  (Generally I know the latter is bad practice should this damage good chips. They all work fgine when put back into the 65XE.)

 

Basically despite the variation in layouts from other revision XLF boards and the obvious differences between my XLF board and a stock 800XL, (ie different layout, lack of a delay line and a few logic chips given the Freddie replaces their function), I have manged to make sense of it and done much research/referencing and then subsequently a lot work to the entire board.

 

As mentioned I've exhausted a lot of avenues aside testing the ICs themselves. This includes the checking continuity of traces/vias to sockets, the sockets themselves, solder work, ICs, and transistors. The notable exception being the passive components, (the caps, resistors, diodes), which I've not replaced.  (BTW I've checked CAPS visually for any signs of failure - nothing stands out). 

 

In summary:

 

• I had found a loose DIN power socket was at fault and cauing the initial lack of power so that was replaced with an identical donor one fairly early on. 
• I'd also replaced a PIA Chip which was initially working and subsequently then when bad.
• I replaced an OS rom chip with a tested/known working one.
• I'd found 2 x bad MT ram chips so ended up replacing the lot, socketing them all in the end.
• 9 x 2N3904 transistors recently replaced witn new ones - just to be sure
• 4 x jumper wires added owing to lifted traces/vias during the desoldering and socketing process. (Involving ANTIC, POKET and a ram chip). Everthing triple checked at the time to ensure the connections restored). I am always careful when desoldering ICs and socketing them - but it happens I guess. I've heard that the XLF PCB's traces aren't quite as robust as the earlier stock 800XL ones)
• Y1 crystal spare from an old donor 130XE swapped in  - but despite being the same rating and fitting on the PCB (in correct orientation as per picture's I referenced), it was a different style/shape crystal. On powering up it just introduced a simple black screen with white lines so assumed it wasn't compatible or was perhaps even broken too. Next I am going to try swapping out the indentical Y1 crystal from my other working stock (PAL) 800XL - just need to get to it in storage to crack it open, remove the sheilding, etc etc, to get to it.

 

FYI I've followed the standard 800XL service manual trouble shooting for Black/grey screens as well as Red/Brown screens, either testing or replacing the components listed, (where my board revision as mentioned above obviously doesn't have certain chips being an XLF rev 3 board).

 

---------------------

 

I also looked at other XLF circuit schematics, although different to my revision 3 board. 

 

So at this stage I am thinking:

• It could still be the Y1 crystal (as mentioned I'll be swapping this out soon to test this when I can get around to it). Just not sure if I'd be getting a red screen, then black and the two audio pops if the crystal wasn't working properly?
• A bad trace(s) somewhere
• A faulty passive component (resistor or diode perhaps?) - I am pretty confident it isn't the transistors or the caps - could be wrong of course with the caps I guess.
•  

Here is the full detailed history as a background:

 

When I first got the 800XLF it wouldn't power up and was totally dead. No signal, no power light. I played around with the socket a little later and realised it's internal assembly was very slightly loose. After moving it a little I got the power light to come on. Unfortunately despite this all way clearly not well with a black screen anyhow.

 

(FYI I am using the same 5v 2amp USB power lead I use for all of my XL/XE A8s which works with all of them.)

 

The whole board's ICs were soldered directly to the PCB, (no sockets), with the exception of the Freddie chip which had a double wipe socket.

Given black screen I wondered at the time if multiple RAM ICs and possibly the CPU and Freddie were dead.

 

Firstly I did the usual - push down and pull up/reseat the socketed Freddie chip - just in case contact had been lost over the years/oxidation had built up. Nothing. Socket looked clear.

 

I generally gave the PCB a good brush down both sides at the start.

 

Starting with the only socketed chip I popped in a couple of known working Freddie chips which didn't seem to make any difference. (I checked the socket for continuity and for any obviously visual issues - nothing - looked ok.)

(FYI the socketed 65XE I use to test ICs initially didn't have a socketed Freddie so I was unable to test the XLF Freddie in the 65XE at that stage)

 

I then decided to test the XLF's CPU chip as another cause of black screens, so had to desolder and socket that to do so. The XLF CPU worked when transfered to my 65XE. I tested the new socket for all the usual just to be sure my solder work, etc had been ok. Checked out ok. Still black screen though.

 

Popped the original Freddie back in the new socket and amazingly the XLF powered up, albeit straight to the self test memory test - where it was clear there was an issue with OS rom and ram.

(Still no clue as to why with the working replacement Freddie and the newly socketed CPU in place it hadn't booted just a short while earlier - possibly indivating a loose connection somewhere(?)).

 

Anyways I confirmed with Sys check II - U12 and U14 Ram bad as was the OS rom chip

 

Two bad chips were then socketed and replaced, where the new non MT brand 120ns chips tested working before being installed using my little DRAM tester. So now there were the 6 x original working MT 120ns Ram chips alongside the two new socketed Non MT ram chips, again all Ram being 120ns.

 

I also needed to swap out the OS rom to replace the bad chip so I had to remove it and install a socket. After removing and popping the OS ROM chip into my 65XE that confirmed the OS rom was bad with Sys check II.

 

I popped a working OS rom chip into the XLF and the system powered up to the blue screen ready prompt.  Eureka!  

 

I tested a game cart and the 64k game played fine - colours looking good on an S-video cable, POKEY working, keyboard, etc.

 

Powered it off after 5 minutes of playing the game..... removed the cart, powered it back on again. Red screen!! Noooooooooooooo!

 

I can't recall why but I decided to replace the MMU next which I socketed. Still a red screen.

 

Whilst I remembered I then replaced the DIN power socket with an indentical one from my donor 130XE PCB.

 

Transplant gave me a new DIN power socket, but of course red screen persisted on power up. (Wasn't expecting the transplant to fix it of course).

 

Frustrated I decided to remove and socket all the RAM and replace with individually tested working non MT ram chips. (No point in just replacing/socketing two chips - the other MT ram was highly likely to go at some stage anyways.)

 

Still red screen.

 

Over the course of several days across a few weekends I then set about socketing the board to remove the ICs to test.

 

I also decided to socket my 65XE's Freddie so it allowed me to put the XLFs Freddie in to test - it worked fine in the 65XE.

 

I tested those newly removed socketed XLF chips in the 65XE where all apart from PIA confirmed working:

 

• The new working OS rom (tested again just to be sure if hadn't gone bad)
• MMU
• CPU
• PIA - found to be bad
• GTIA
• 4050
• Atari BASIC ROM
• ANTIC
• POKEY
• 74LS74AN
• 74LS138N
• 74LS08 (and subsequently it's new replacement the 74F08N)

 

I replaced the PIA with a tested working one - made no difference - red screen.

 

So to clarify I've socketed the entire board, tested after each socket was installed.

 

The only ICs on the board not removed or socketed are the two keyboard related ICs (the 4051 MUX ICs).

 

I've since socketed the 8 pin IC's 555 and 358N too and put known working replacement ICs in place.

 

I've triple checked ALL of the sockets and continuity between the ICs and their sockets, with the top and underside of the PCB with each socket, and as much as possible due to access I've checked traces coming off ICs and their sockets for continuity. I'd found a small handful of bad traces coming off vias for the PIA, Pokey, ANTIC and one ram chip - all fixed with jumper wires and triple checked for continuity and to ensure no shorting has been introduced. (4 x jumper wires added overall).

 

Again very early on all the MT ram was replaced with tested working RAM chips, (as I found those 2 x bad MT chip initially). 

 

Y1 crystal spare from an old donor 130XE swapped in  - but despite being the same rating and fitting on the PCB (in correct orientation as per picture's I referenced), it was a different style/shape crystal. On powering up it just introduced a simple black screen with white lines so assumed it wasn't compatible or was perhaps even broken too. Next I am going to try swapping out the indentical Y1 crystal from my other working stock (PAL) 800XL - just need to get to it in storage to crack it open, remove the sheilding, etc etc, to get to it.

 

I've since replaced all of the 9 x 2N3904 transistors with new tested working ones.

 

Could the fact after the OS rom and ram was sorted and the machine appeared working, that the DIN power socket then caused a surge at some stage and further damaged the PIA which then needed replacing, as well as some passive components. Transistors were replaced long after the new replacement DIN socket was installed - so I am confident the new transistors are ok.

 

So at this stage I am thinking:

• It could still be the Y1 crystal (as mentioned I'll be swapping this out soon to test this when I can get around to it). Just not sure if I'd be getting a red screen, then black and the two audio pops if the crystal wasn't working properly?
• A bad trace(s) somewhere
• A faulty passive component (resistor or diode perhaps?) - I am pretty confident it isn't the transistors or the caps - could be wrong of course with the caps I guess.

Thanks for reading.

 

Edited February 20, 2022 by Beeblebrox

[TGB1718]

Sounds like you need a scope

So much easier to trace signals around a board, not sure if there's a SAM's for your machine,

but it usually does show expected signal waveforms around the board.

[Beeblebrox]

@TGB1718   Yeah it had crossed my mind but I saw the cost of a halfway decent scope a few months back and it wasn't cheap! Guess I'll have another look around. It is one of those things I could do with.

 

There are plenty of schematics and reference guides for stock 800XLs but for this particular rev 3 XLF there isn't much about.

 

I am really hoping this will turn out to be the crystal having died recently, but I suspect the likelyhood of some passive componetry issues causing problems is high too.

That is where my lack of electronics smarts fail me as trying to decipher circult diagrams and dealing with individual resistors, diodes, etc, is a real challenge for me to get my head around.

 

I'll try swapping the Y1 crystal out for a 2nd time with another and see what happens.

Edited February 20, 2022 by Beeblebrox
typo

[TGB1718]

Generally the only way to test a resistor or diode is to lift one leg due to parallel components

which obviously means the possibility of more damage to tracks.

 

I bought a Pico Scope some time back cost me £99, it does require a PC/Laptop

for the display, which for me was no problem as I have old laptops coming out of my ears

 

Dual channel up to 10MHz, ideal for low voltage circuits.

 

[Mclaneinc]

Adrian of Adrian's Digital Basement YT channel was showing off a very cheap scope in a vide about a week ago, it was $60.00 iirc and in his opinion was enough for low voltage stuff like C64's / Ataris, single channel and needs a laptop but he found it usable and found an open source set of software that was better than what came with it.

 

 

 

And here's one where he uses it to do a repair..

 

 

[Beeblebrox]

Thanks for the suggestions and advice re Scopes.  I'll be looking into it.

 

OK - update - I swapped the XLF's Y1 crystal out for a known working one, popping the XLF's Y1 crystal into my other working A8 and visa versa. The crystal isn't at fault as it working in my other working A8 no problems. Unfortunately still no joy getting the XLF to work. 

 

So at least it isn't the Y1 crystal contributing/causing the problem.

 

Red screen than black screen persists. 

 

The investigation continues.

Edited February 20, 2022 by Beeblebrox

[TGB1718]

1 hour ago, Mclaneinc said:

Adrian of Adrian's Digital Basement YT channel was showing off a very cheap scope in a vide about a week ago, it was $60.00 iirc and in his opinion was enough for low voltage stuff like C64's / Ataris, single channel and needs a laptop but he found it usable and found an open source set of software that was better than what came with it.

 

I bought one of those before the Pico, sent it back because the software would hang/crash, though as you say there's now

some open source software that may be better, I ended up sending back for a refund.

[Mclaneinc]

I have never used a scope, I know only what I have seen others do, but I'd personally have no use for one, you might as well ask me to do brain surgery instead of trying to fault find with a scope

 

Glad someone knew of that model and could offer better help.

[Beeblebrox]

Ok - bit of progress this afternoon it seems. I've at last gotten sys check II to kick in again!

 

After the system consistently started showing the red screen of death, (and then black), all the way throught this attempted fix I been plugging my trusty Sys Check II in on the offchance it would kick in.

 

Given the apparent display problems everytime I did, no matter what preset on the Sys Check II, I was just getting the red screen, either on it's own or with vertical bars, (usually one or two pink verticals on the red background).

 

Anyway, after trying the Y1 crystal swap as mentioned earlier this afternoon and that having no effect powering up, (even when then tested with Sys check II plugged in), I did a bit more research.

 

I decided to install Tf_hh's 100nf capacitor power mod just on the offchance it made some kind of difference. It didn't. (If I ever get this machine working it'll be worth doing in advance of the U1MB I plan to install).

 

I then decided to replace the socket for the Basic Rom chip, to bring it in line with the other precision sockets used. (I'd not had a spare 24pin precision socket the other week when I'd socketed the Basic rom and had used a new double wipe one).

Before I replaced the socket again I tried booting the machine without the Basic rom plugged into the existing double wipe socket. (I'd heard the A8 can boot without the Basic chip installed). No difference.

 

So after I'd removed the socket and taking the opportunity to text the traces for continuity, etc, the new socket went in and so did the Basic rom chip. Powering it up  - no change. Red then black screen.

 

I popped the sys check II in and had it set to the default mode I always use initially:

 

...powering up I then was at long last reunited with the Sys check II diagnostic kicking in!!!  

 

Now we're getting somewhere as not seen this for many days of working on this - no matter what I'd tried:

 

 

It quickly indicated bad ram, (menu colour turns red as it is checking as you can see), but then something odd happened. At around the high end memory registers(?) - around $8000 in the check - the numbers start to go a lil mad as it checked them, and when it finished it totaly bypassed the OS rom check and jumped to the results screen, showing the 800XLF related results in the 2nd column:

 

    

 

I ran it a few more times - including after powering it all off for a good 30 seconds -  and it seems that the bad ram it reports is random. Sometime a few chips, sometimes all:

 

 

However I've seen this false bad ram result happen with Sys Check II before when a Bad OS rom chip was in place - so I replaced the OS rom with another known to work. Same issue.

 

I then replaced the MMU with a known working chip given it's involvement in RAM management. Same issue.

 

I removed all the RAM chips one by one and put them in my little DRAM tested. All of them checked out ok.

 

I then touched up the solder of all the RAM sockets from under the board, checked for shorts, continuity, etc.

 

Same issue with Sys check - bad ram reported and it totally bypasses the OS rom check.

 

I tried using the other setting I sometimes use on Sys check II:

 

... but there I just get a red screen and no Sys check II kicking in. However given the above setting uses the XLF's own RAM, I am not surprised this didn't work.

 

So it appears the issue lies with the memory or memory management, and/or possible something to do with the OS rom presumbly?

 

Given the RAM chips all indepentantly check out as good when off the board and I put in known working MMU and OS ROM which made no difference,  I am drawing the following possble conclusions:

 

1) One or more of the Ram sockets have an issue (bad connection?)

2) The MMU socket is at fault

3) The OS rom or it's socket is somehow at fault

4) Some supporting passive componentry involved in the RAM is off - I doubt this TBH.

 

At this point I am pretty resistant to the idea of removing the all of the RAM sockets one by one and replacing them.

I was very careful installing them in the first place and continuity checks out. The jumper wire in place for that one trace lift is definitely working.

 

Aside from being labour intensive and time consuming, doing so would only likely increase the chances of more heat damage to that area of the PCB to find a possible bad socket.

 

I might revisit removing the MMU's precision socket and also the OS rom precision socket,  although again all the continuity checks out. 

 

I wonder - at this point does anyone have any suggestions in light of these new developments? Anything else to consider?

 

At least now I am pretty certain there is no fault with the main 40pin ICs, CPU, ANTIC and GTIA or the display circuit and that the problem it's related to RAM, ram management and/or the OS Rom. Of course, that is just an educated guess.

 

After literally the equivalent of 6 x days working on this it is somewhat a relief to see the Sys check II screen kick in at last. 

 

thanks for reading

 

 

[Beeblebrox]

@kheller2  @TGB1718   @Mclaneinc

 

Woohoo!! Nailed it!!

 

Thanks for your replies in this thread guys - much appreciatedas ever.

 

So with the last piece of the puzzle it finally came down to a very small previously overlooked partial broken trace/via on one pin of a RAM chip for the last hurdle!! 

 

In a nut shell I decided to check the continunity of the RAM traces again as really wasn't looking to pull up the RAM sockets in a hurry and potentially do far more damage in the process.

 

I've done this continuity check before a few times over the course of the fix with these RAM chips but it looks like I omitted checking just one trace on one side of a via on pin 9 of U13, which has a tiny brake one side of said trace here top side:

(FYI the image below is of another revision XLF unpopulated PCB which happens to have the same RAM traces as my rev 3 board, (for the most part - there were some differences))

 

 

This brake in the trace line was enough to break the line of continuity for the rest of the pin 9 to pin 9 connections all the way down the line to the U9 RAM chip.

 

Soon as I jumpered the two pins for U13 and U12 on the underside of the PCB with a small wire - it powered up no problems!!  

 

 

Ah the relief!!!! Three weekends, (and then some), trying to get to the bottom of this and get it back up and running.

 

Icing on the cake is that assembled the keyboard and function keys work with no issues!! (I really was expecting some keys not to work).

 

Worth noting I've completely socketed a good few A8 PCBs successfully now, including a lot of 40pin ICs as well as ram chips on XLs and XEs - so I consider this bad luck as I was really careful. (Guess it's gonna happen - I'll keep telling myself that!)

 

So it appears overall this rev 3 800XLF had the following issues/fixes:

 

• There was a loose/bad DIN power socket - replaced with an identical donor one from an 130XE
• 2 x BAD MT branded RAM chips initially - all 8 x MT chips replaced and fully socketed
• An issue that saw the ROM OS and PIA chip then subsequently die on me shortly after the XLF had been running a game.
• A small handful of broken traces when I was attempting to remove and socket ANTIC, POKEY and RAM. (I am telling myself that 5 x bad traces considering I've socketed virtually the entire board ain't too bad!)
• Final discovery of a small trace/via break which was further fixde with a small jumper wire.
• Whole board - with the exception of 2 x 4051 ICs - is now socketed in preparation for the U1MB if I decide to install it in this XL.

 

Lessons learnt:

 

• Replace the power socket sooner - I had been so pleased to have it initially running I shouldn't have played the game. Next time I'll power it off straight away and replace the DIN socket. (Of course whilst the power socket issue may have cause the OS ROM and PIA issues, there was no guarantee that these chips weren't their way out I guess anyway. I don't think this A8 had been powered up for 20+ years by the state of it))
• Quadruple check continuity and if in doubt double check again. This last one was small but was the key.
• In the process of all the socketing trace and via damage occurred - despite being careful - so next time be even more careful.
• Buy a scope!!

 

Everything seems to be running - touch wood - I just need to clean up the casing and keyboard:

 

            

 

 

           

 

        

 

 

       

 

Edited February 20, 2022 by Beeblebrox

[TGB1718]

Glad you got it going, perseverance paid off ?

[Beeblebrox]

@TGB1718  Thanks - my other half thinks I'm mad the amount of time spent fixing these up! (Keeps me out of mischief!)

 

*************

BTW before I reassembled this XLF I did clip the plastic cartridge cage back on the board - just in case anyone was thinking it was missing.

 

Just played a 5min session of The Last Squadron on this XLF. Love that game.

[Mclaneinc]

Congrats, been following this...Excellent result and great help people!