800XL startup RAM test fail options

[WOPRpwJOSHUA]

Hi all, new to AA and what seems like a great community. Was recently given an 800XL that fails a pre-BASIC memory test. This is a non-socketed board from Nov. '84 ("800XL C061851 REV D KO SHENG 4684"), has the MT memory chips, and (type 4) Stackpole keyboard. I have read the several threads here I could find (thanks) but wanted some clarity - other than purchasing a diagnostic device (re: syscheck etc.), swapping out/stacking good chips to test/find bad ones, is there any other technique to try before desoldering everything? I have no donor boards/components - this was given w/o any peripherals or carts - and I've not yet looked into acquiring any (other than I know there are various diagnostic devices, which I will look into if that's the expedient option). I'll mention, it shows the same 4 good blocks at start, the buttons including RESET work, holding OPTION when powering on still results in pre-BASIC mem fail, and the power brick is a non-Ingot showing 5.124V (no load). I've opened it up and taken pics, will post if that helps.

 

For context, it's sat in it's original packaging untouched/unused since '89 when purchased 'two NOS, this one as a backup' - knowing the guy, inspecting everything, I'm sure this was the case. Looks like he purchased it from Federated in Ft. Worth, TX, the day they were closing down (he documents everything and keeps receipts..).

Edited March 27 by WOPRpwJOSHUA
clarity

[_The Doctor__]

only 4 good blocks?

sounds like memory then check it's support chip then it's pia in that order to check

[Beeblebrox]

Yup, as above. 

Defo get rid of mtram. Socket and pop in some other brand. Hopefully that will be the only issue. Can be other things but ram is the first fix here. 

 

Edit in a rush but have a look here for ref to equivalent drams to use :

 

 

 

Edited March 28 by Beeblebrox

[+scorpio_ny]

Welcome @WOPRpwJOSHUA!

 

MT RAM is notorious for being bad on many platforms. Definitely replace all of them as a starting point. When I get a computer and I see MT RAM on it, Even if it is working, I usually schedule chip replacement as a proactive action

[Beeblebrox]

20 minutes ago, scorpio_ny said:

Welcome @WOPRpwJOSHUA!

 

MT RAM is notorious for being bad on many platforms. Definitely replace all of them as a starting point. When I get a computer and I see MT RAM on it, Even if it is working, I usually schedule chip replacement as a proactive action

@scorpio_nyI agree, although @WOPRpwJOSHUA I'd add where you have no sockets present for RAM, (all XEs, and Taiwanese made 800XLs), only attempt to remove these if you have fairly good experience with desoldering and soldering. Sure, you can clip the legs off all old ram, remove them, clean the vias up, etc before adding in sockets. You can also use a solder pump or electric desolder gun to remove solder and pry the chips out, (I do this all the time). However it's done, without experience with a soldering iron you can damage things and given you would likely be replacing all 8 x dram chips, you potentially have some fiddly troubleshooting if there is damage or shorts are present after work. 

 

Worth noting some use a heat gun to heat up and remove the chips. You can do this, but be warned, it's a large area of the board to be applying heat to, and you can risk warping the board badly.

 

I always snap a few hi res images of the board vias after ram chips are removed, after all is cleaned up, prior to checking the vias and traces, and then adding sockets. It's painstaking work, but worth the effort. If any issues you can reference the photos, and use a multimeter to check things. Then if jumpers are needed or shorts are present, you can fix it.

 

Also, with ram sockets, use double wipe ones. Avoid the round turned precision sockets. The ram chips can be a pain to get their legs into said sockets, but the main issue is they can work loose once in. Double wipe sockets really hold onto them and are generally my go to for 16pin drams. For others, (20, 24, 28 and 40 pin), I tend to favour precision sockets. For example, whist a 40pin double wipe socket really holds onto the likes of the Sophia2 or other 40pin based boards really well, if you ever want to remove them, they can increase the potential for damaging the upgrade's pcb in attempting too. I've been sweating buckets tentatively prying up a Sophia2 in the past. Really thought I'd damaged it once. Always use the right tools too.  

 

Anyway, I digress.

Edited March 28 by Beeblebrox

[TZJB]

13 hours ago, WOPRpwJOSHUA said:

Hi all, new to AA and what seems like a great community. Was recently given an 800XL that fails a pre-BASIC memory test. This is a non-socketed board from Nov. '84 ("800XL C061851 REV D KO SHENG 4684"), has the MT memory chips, and (type 4) Stackpole keyboard. I have read the several threads here I could find (thanks) but wanted some clarity - other than purchasing a diagnostic device (re: syscheck etc.), swapping out/stacking good chips to test/find bad ones, is there any other technique to try before desoldering everything? I have no donor boards/components - this was given w/o any peripherals or carts - and I've not yet looked into acquiring any (other than I know there are various diagnostic devices, which I will look into if that's the expedient option). I'll mention, it shows the same 4 good blocks at start, the buttons including RESET work, holding OPTION when powering on still results in pre-BASIC mem fail, and the power brick is a non-Ingot showing 5.124V (no load). I've opened it up and taken pics, will post if that helps.

 

For context, it's sat in it's original packaging untouched/unused since '89 when purchased 'two NOS, this one as a backup' - knowing the guy, inspecting everything, I'm sure this was the case. Looks like he purchased it from Federated in Ft. Worth, TX, the day they were closing down (he documents everything and keeps receipts..).

 

Welcome to AtariAge.

 

Sorry to hear that you are suffering with 800XL RAM failure.

 

The voltage indicated is fine. What is the voltage on load measured across the 7 pin DIN connector?

 

Diagnostic devices are not necessary at this point in time due to the fact that the 800XL is showing the RAM test, indicating that everything else is probably working fine.

 

If you have some isopropyl alcohol, one trick to finding bad RAM is to place a drop on each chip with the power off, then turn the machine on. The faulty DRAM chips can invariably get hotter which is indicated by faster evaporation of the liquid.

 

This is not foolproof however and as most members have advised, it's best to change them all for either 4164 or 41256 or compatible DRAM manufactured by an alternative brand!

 

I am a proponent of 41256 DRAM due to the easy upgrade path to a Rambo XL which expands the memory with an extra 192KB, but that can be done much later or not at all.

 

If you are wondering how 41256 DRAM can also work as standard 64K memory, DRAM pin 1 (ADD8) is held high and thus disabled via the R32 3K resistor.

 

This also makes the Rambo XL easier to wire if you decide to, by desoldering said resistor and adding the Rambo XL decode circuit board connection to ADD8.

 

There are multiple discussions of this topic here on AtariAge.

 

[Beeblebrox]

53 minutes ago, TZJB said:

 

Welcome to AtariAge.

 

Sorry to hear that you are suffering with 800XL RAM failure.

 

The voltage indicated is fine. What is the voltage on load measured across the 7 pin DIN connector?

 

Diagnostic devices are not necessary at this point in time due to the fact that the 800XL is showing the RAM test, indicating that everything else is probably working fine.

 

If you have some isopropyl alcohol, one trick to finding bad RAM is to place a drop on each chip with the power off, then turn the machine on. The faulty DRAM chips can invariably get hotter which is indicated by faster evaporation of the liquid.

 

This is not foolproof however and as most members have advised, it's best to change them all for either 4164 or 41256 or compatible DRAM manufactured by an alternative brand!

 

I am a proponent of 41256 DRAM due to the easy upgrade path to a Rambo XL which expands the memory with an extra 192KB, but that can be done much later or not at all.

 

If you are wondering how 41256 DRAM can also work as standard 64K memory, DRAM pin 1 (ADD8) is held high and thus disabled via the R32 3K resistor.

 

This also makes the Rambo XL easier to wire if you decide to, by desoldering said resistor and adding the Rambo XL decode circuit board connection to ADD8.

 

There are multiple discussions of this topic here on AtariAge.

 

@WOPRpwJOSHUAJust to add, rambo xl will only work in stock 800xl machines and not 800xlf machines, (the 800xl with a Freddie chip).

 

Post a pic of your 800xl's main board if in doubt. From the outside the look identical. 

Edited March 28 by Beeblebrox

[WOPRpwJOSHUA]

Apologies all, having some strange network issues- thanks to everyone so far, everyone's been very helpful.

[WOPRpwJOSHUA]

3 hours ago, Beeblebrox said:

@WOPRpwJOSHUAJust to add, rambo xl will only work in stock 800xl machines and not 800xlf machines, (the 800xl with a Freddie chip).

 

Post a pic of your 800xl's main board if in doubt. From the outside the look identical. 

Here's a few of the board

AA800XL.heic AA800XL2.heic AA800XL3.heic

[WOPRpwJOSHUA]

10 hours ago, _The Doctor__ said:

only 4 good blocks?

sounds like memory then check it's support chip then it's pia in that order to check

Thanks Doc, looks like this is the way.

[WOPRpwJOSHUA]

5 hours ago, scorpio_ny said:

Welcome @WOPRpwJOSHUA!

 

MT RAM is notorious for being bad on many platforms. Definitely replace all of them as a starting point. When I get a computer and I see MT RAM on it, Even if it is working, I usually schedule chip replacement as a proactive action

This makes sense, I'll do this as a standard going fwd, thanks.

5 hours ago, Beeblebrox said:

@scorpio_nyI agree, although @WOPRpwJOSHUA I'd add where you have no sockets present for RAM, (all XEs, and Taiwanese made 800XLs), only attempt to remove these if you have fairly good experience with desoldering and soldering. Sure, you can clip the legs off all old ram, remove them, clean the vias up, etc before adding in sockets. You can also use a solder pump or electric desolder gun to remove solder and pry the chips out, (I do this all the time). However it's done, without experience with a soldering iron you can damage things and given you would likely be replacing all 8 x dram chips, you potentially have some fiddly troubleshooting if there is damage or shorts are present after work. 

 

Worth noting some use a heat gun to heat up and remove the chips. You can do this, but be warned, it's a large area of the board to be applying heat to, and you can risk warping the board badly.

 

I always snap a few hi res images of the board vias after ram chips are removed, after all is cleaned up, prior to checking the vias and traces, and then adding sockets. It's painstaking work, but worth the effort. If any issues you can reference the photos, and use a multimeter to check things. Then if jumpers are needed or shorts are present, you can fix it.

 

Also, with ram sockets, use double wipe ones. Avoid the round turned precision sockets. The ram chips can be a pain to get their legs into said sockets, but the main issue is they can work loose once in. Double wipe sockets really hold onto them and are generally my go to for 16pin drams. For others, (20, 24, 28 and 40 pin), I tend to favour precision sockets. For example, whist a 40pin double wipe socket really holds onto the likes of the Sophia2 or other 40pin based boards really well, if you ever want to remove them, they can increase the potential for damaging the upgrade's pcb in attempting too. I've been sweating buckets tentatively prying up a Sophia2 in the past. Really thought I'd damaged it once. Always use the right tools too.  

 

Anyway, I digress.

I've got an electric desolder gun and will be careful to avoid pulling up pads etc. Have a heat gun too (w/reducing tips for this work) but won't use unless necessary. I'm used to documenting thoroughly (working on old turntable etc. quickly instills there's no easy way to replace various bits). I'll get some dual wipe sockets for the board and replace all the ram, thanks for all of the detail and advice.

[WOPRpwJOSHUA]

5 hours ago, TZJB said:

 

Welcome to AtariAge.

 

Sorry to hear that you are suffering with 800XL RAM failure.

 

The voltage indicated is fine. What is the voltage on load measured across the 7 pin DIN connector?

 

Diagnostic devices are not necessary at this point in time due to the fact that the 800XL is showing the RAM test, indicating that everything else is probably working fine.

 

If you have some isopropyl alcohol, one trick to finding bad RAM is to place a drop on each chip with the power off, then turn the machine on. The faulty DRAM chips can invariably get hotter which is indicated by faster evaporation of the liquid.

 

This is not foolproof however and as most members have advised, it's best to change them all for either 4164 or 41256 or compatible DRAM manufactured by an alternative brand!

 

I am a proponent of 41256 DRAM due to the easy upgrade path to a Rambo XL which expands the memory with an extra 192KB, but that can be done much later or not at all.

 

If you are wondering how 41256 DRAM can also work as standard 64K memory, DRAM pin 1 (ADD8) is held high and thus disabled via the R32 3K resistor.

 

This also makes the Rambo XL easier to wire if you decide to, by desoldering said resistor and adding the Rambo XL decode circuit board connection to ADD8.

 

There are multiple discussions of this topic here on AtariAge.

 

Thanks! Great to be here.

I'll measure load when I have access later, post it back here.

 

I'll be sure to order 41256 replacements and of another brand - I'll have another look through the threads for the most suggested brands/sites as well, and I'll be sure to replace them all. Thanks much for the detailed info!

[WOPRpwJOSHUA]

On 3/28/2024 at 8:22 AM, TZJB said:

 

Welcome to AtariAge.

 

Sorry to hear that you are suffering with 800XL RAM failure.

 

The voltage indicated is fine. What is the voltage on load measured across the 7 pin DIN connector?

 

Diagnostic devices are not necessary at this point in time due to the fact that the 800XL is showing the RAM test, indicating that everything else is probably working fine.

 

If you have some isopropyl alcohol, one trick to finding bad RAM is to place a drop on each chip with the power off, then turn the machine on. The faulty DRAM chips can invariably get hotter which is indicated by faster evaporation of the liquid.

 

This is not foolproof however and as most members have advised, it's best to change them all for either 4164 or 41256 or compatible DRAM manufactured by an alternative brand!

 

I am a proponent of 41256 DRAM due to the easy upgrade path to a Rambo XL which expands the memory with an extra 192KB, but that can be done much later or not at all.

 

If you are wondering how 41256 DRAM can also work as standard 64K memory, DRAM pin 1 (ADD8) is held high and thus disabled via the R32 3K resistor.

 

This also makes the Rambo XL easier to wire if you decide to, by desoldering said resistor and adding the Rambo XL decode circuit board connection to ADD8.

 

There are multiple discussions of this topic here on AtariAge.

 

Hi @TZJB, w/load I get 5.071V (at board connector), looks good?

I'll look for replacement sockets and RAM tonight and this weekend.

Any other IC or components that you folks generally replace as a standard on these 800XL's? Feel free to reply, I'll check back while I'm tracking down replacements, thanks

PS: a few other pics of condition and packaging. What will you do with all this extra memory?

AA8XLbox.heic AA8XLbox2.heic AA8XLbox3.heic AA8XLkb.heic AA8XLkb2.heic AA8XLkb3.heic AA8XLkb4.heic AA8XLog.heic AA8XLsw.heic

[TZJB]

13 hours ago, WOPRpwJOSHUA said:

Hi @TZJB, w/load I get 5.071V (at board connector), looks good?

I'll look for replacement sockets and RAM tonight and this weekend.

Any other IC or components that you folks generally replace as a standard on these 800XL's? Feel free to reply, I'll check back while I'm tracking down replacements, thanks

PS: a few other pics of condition and packaging. What will you do with all this extra memory?

AA8XLbox.heic 2.09 MB · 2 downloads AA8XLbox2.heic 2.18 MB · 2 downloads AA8XLbox3.heic 1.97 MB · 2 downloads AA8XLkb.heic 1.76 MB · 1 download AA8XLkb2.heic 2.42 MB · 2 downloads AA8XLkb3.heic 2.24 MB · 2 downloads AA8XLkb4.heic 2.48 MB · 2 downloads AA8XLog.heic 2 MB · 3 downloads AA8XLsw.heic 2.97 MB · 2 downloads

 

5.071V at J7, the DIN connector, is fine.

 

However AtariAge does not support the HEIC picture format so it's a bit difficult to view the images. I have had to download and convert them.

 

Saying that, on viewing your pictures, the machine is in very good nick and is a standard NTSC 800XL so can be upgraded to 256KB easily if you should so desire, with the two extra chips decoder version, as your ANTIC is C021697 as expected in a 800XL.

 

Note that the PSU leads are showing signs of plasticiser leakage due to contact with the polysyrene box, so separate them as soon as possible or the cable will become hard, and the same for the aerial connecting cable.

 

Vary rarely C1 470uF 16V will need to be changed, otherwise there will not normally be anything else to change in a 800XL unless other faults become apparent. Additionally I have taken to installing a 5.6V 1W zener diode directly across J7 to provide some sort of cheap over-voltage protection. Other upgrades are available .

 

Regarding extra memory, it can be used by individual programs such as word processors and other utilities, and is extensively used as a RAMdisk by various DOS versions. It will be detected by older programs as 130XE compatible, but newer programs can use it all.

 

Incidentally, the Rambo XL was a commercialised version of Claus Buchholz 130XE-COMPATIBLE 800XL 256K UPGRADE.

 

We have to thank @ClausB for his work and foresight on this.

 

 

130XE-COMPATIBLE 800XL 256K UPGRADE ClausB.txt

 

 

[WOPRpwJOSHUA]

9 hours ago, TZJB said:

 

5.071V at J7, the DIN connector, is fine.

 

However AtariAge does not support the HEIC picture format so it's a bit difficult to view the images. I have had to download and convert them.

 

Saying that, on viewing your pictures, the machine is in very good nick and is a standard NTSC 800XL so can be upgraded to 256KB easily if you should so desire, with the two extra chips decoder version, as your ANTIC is C021697 as expected in a 800XL.

 

Note that the PSU leads are showing signs of plasticiser leakage due to contact with the polysyrene box, so separate them as soon as possible or the cable will become hard, and the same for the aerial connecting cable.

 

Vary rarely C1 470uF 16V will need to be changed, otherwise there will not normally be anything else to change in a 800XL unless other faults become apparent. Additionally I have taken to installing a 5.6V 1W zener diode directly across J7 to provide some sort of cheap over-voltage protection. Other upgrades are available .

 

Regarding extra memory, it can be used by individual programs such as word processors and other utilities, and is extensively used as a RAMdisk by various DOS versions. It will be detected by older programs as 130XE compatible, but newer programs can use it all.

 

Incidentally, the Rambo XL was a commercialised version of Claus Buchholz 130XE-COMPATIBLE 800XL 256K UPGRADE.

 

We have to thank @ClausB for his work and foresight on this.

 

 

130XE-COMPATIBLE 800XL 256K UPGRADE ClausB.txt 5.24 kB · 4 downloads

 

 

My mistake, let me know if it's helpful (or not too spammy) and I can add jpg's (and if a MOD is inclined to delete the HEIF's). 

 

I will plan on the 256KB upgrade, so I'll look for that 2 chip decoder version, thanks. 

 

I'd noticed the leaching (one reason I trusted the guy stored it as-bought/untouched since '89) and have the box/packaging stored in a closet. Leads feel fine, the switch box cable does feel a bit stiff though - thanks for the head's up. 

 

Good idea on the zener - I will def add that, and would be interested in other upgrades (and/or I can explore the forum for them if that's better). 

 

I've read a bit on the Rambo XL and will look fwd to adding that one (and thanking @ClausB). 

 

41256 DRAM and sockets ordered. Looking over various potential upgrades/mods, as well as videos of work done by others (some members here I think too). 

I'll start desoldering and prepping the board tomorrow. 

 

My approach is to fix-first then stage any upgrades so that I'm not walking (or too much) over any previous work - so any suggestions or considerations for that are well appreciated (and I'll continue to read up on that where I find it). 

 

Are there a lot of "Ko Sheng" mfd boards in these 800XL's? Found only a few mentions at all of that entity (relating to the 65XE/900XLF). 

I should look into a multicart as well...

 

 

 

 

 

[Beeblebrox]

@WOPRpwJOSHUA  so I downloaded your image files and had a look.

 

Good news is you have a rev d 800xl board. Ntsc. 

 

So a rambo xl upgrade will work. It's fairly straightforward to install, but involves socketing ram and replacing with the 256k chips, socketing the upper 74ls158 chip, which the rambo xl board goes in, and also socketing the pia 6520 chip far right of the board. Then a few dupont wires. 

 

See here:

https://forums.atariage.com/topic/351328-rambo-800xl-sm-version/?do=findComment&comment=5310851

I am in the UK and get this premade rambo xl board:

 

https://www.ebay.co.uk/itm/266673794264

 

.. And these 256k chips:

8 x HM51256LP-15 Fast Page DRAM 256K X 1 150ns CMOS 16-Pin DIP

https://www.ebay.co.uk/itm/273100954587?

 

Or there are PBI plugins options for ram upgrades which are plug and okay:

https://forums.atariage.com/topic/336161-320k-parallel-port-ram-upgrade-for-600xl-800xl/?do=findComment&comment=5252720

To buy here:

https://www.tindie.com/products/5cfab/320k-memory-upgrade-for-the-atari-xl-computers/

 

You'll also likely wish to hook up chroma to use svideo,  which is a superior video output on the 800xl, but doesn't come ready from factory. A simple wire with a 100ohm resistor in it, hooked up to the chroma pin 5 on the din5:

 

https://forums.atariage.com/topic/350787-gifting-a-new-build-of-the-800xl/?do=findComment&comment=5265009

 

 

This old image I quickly found shows topside of the board, but you can do this on the underside, just don't forget the 100ohm resistor and heatshrink :

 

 

Edited March 31 by Beeblebrox

[aeberbach]

On 3/28/2024 at 11:46 PM, Beeblebrox said:

Also, with ram sockets, use double wipe ones. Avoid the round turned precision sockets. The ram chips can be a pain to get their legs into said sockets, but the main issue is they can work loose once in. Double wipe sockets really hold onto them and are generally my go to for 16pin drams. For others, (20, 24, 28 and 40 pin), I tend to favour precision sockets.

Just one caution on those precision aka machined sockets - when they are in, they are not coming out. Conventional sockets and ICs I can remove easily with the desoldering pump - they come free every time, 2 minutes work for 40 pins. The round pin sockets sit right on top of the holes and do not leave any room for air, so the solder can’t be sucked out neatly. Flat pins do leave room for air and the FR310 can suck all the solder right out of there.

 

i found this out the hard way yesterday. I had an 800XL with no sockets where I desoldered everything and socketed it all with my new 40-pin “precision” sockets. Then after just a few insertions noticed that chips were practically falling out and that I had been a complete idiot buying from eBay rather than brand-name sockets from an actual electronics distributor. None of the sockets came loose with the desoldering pump. All needed to be cut with a dremel wheel and each pin removed individually. Out of 200 holes I was lucky only to have to repair two traces, but the machine is now working again and 20 “precision” 40-pin sockets (or their component parts) are now in the bin. I’m buying a stock of AMP sockets.

[Beeblebrox]

2 minutes ago, aeberbach said:

Just one caution on those precision aka machined sockets - when they are in, they are not coming out. Conventional sockets and ICs I can remove easily with the desoldering pump - they come free every time, 2 minutes work for 40 pins. The round pin sockets sit right on top of the holes and do not leave any room for air, so the solder can’t be sucked out neatly. Flat pins do leave room for air and the FR310 can suck all the solder right out of there.

 

i found this out the hard way yesterday. I had an 800XL with no sockets where I desoldered everything and socketed it all with my new 40-pin “precision” sockets. Then after just a few insertions noticed that chips were practically falling out and that I had been a complete idiot buying from eBay rather than brand-name sockets from an actual electronics distributor. None of the sockets came loose with the desoldering pump. All needed to be cut with a dremel wheel and each pin removed individually. Out of 200 holes I was lucky only to have to repair two traces, but the machine is now working again and 20 “precision” 40-pin sockets (or their component parts) are now in the bin. I’m buying a stock of AMP sockets.

Very true. 

[Dopeyman06]

2 hours ago, Beeblebrox said:

@WOPRpwJOSHUA  so I downloaded your image files and had a look.

 

Good news is you have a rev d 800xl board. Ntsc. 

 

So a rambo xl upgrade will work. It's fairly straightforward to install, but involves socketing ram and replacing with the 256k chips, socketing the upper 74ls158 chip, which the rambo xl board goes in, and also socketing the pia 6520 chip far right of the board. Then a few dupont wires. 

 

See here:

https://forums.atariage.com/topic/351328-rambo-800xl-sm-version/?do=findComment&comment=5310851

I am in the UK and get this premade rambo xl board:

 

https://www.ebay.co.uk/itm/266673794264

 

.. And these 256k chips:

8 x HM51256LP-15 Fast Page DRAM 256K X 1 150ns CMOS 16-Pin DIP

https://www.ebay.co.uk/itm/273100954587?

 

Or there are PBI plugins options for ram upgrades which are plug and okay:

https://forums.atariage.com/topic/336161-320k-parallel-port-ram-upgrade-for-600xl-800xl/?do=findComment&comment=5252720

To buy here:

https://www.tindie.com/products/5cfab/320k-memory-upgrade-for-the-atari-xl-computers/

 

You'll also likely wish to hook up chroma to use svideo,  which is a superior video output on the 800xl, but doesn't come ready from factory. A simple wire with a 100ohm resistor in it, hooked up to the chroma pin 5 on the din5:

 

https://forums.atariage.com/topic/350787-gifting-a-new-build-of-the-800xl/?do=findComment&comment=5265009

 

 

This old image I quickly found shows topside of the board, but you can do this on the underside, just don't forget the 100ohm resistor and heatshrink :

 

 

I've done quite a few (underside method) without adding the resistor and the output looks very good. So why the 100Ω resistor?

 

[Beeblebrox]

45 minutes ago, Dopeyman06 said:

I've done quite a few (underside method) without adding the resistor and the output looks very good. So why the 100Ω resistor?

 

It's a well known addition related to colour output. Not essential, but I've always done it. 

 

See FJC's explanation :

 

https://forums.atariage.com/topic/322272-chromaluma-for-s-video-in-800xl/?do=findComment&comment=4851962

 

Edited March 31 by Beeblebrox

[Dopeyman06]

11 minutes ago, Beeblebrox said:

It's a well known addition relatesd to colour output. Not essential, but I've always done it. 

 

See FJC's explanation :

 

https://forums.atariage.com/topic/322272-chromaluma-for-s-video-in-800xl/?do=findComment&comment=4851962

 

Ahhh ok. Thanks for that link. He mentioned YMMV and I've never encountered the need to add it.

[thorfdbg]

The memory test in the selft test is mostly fake - the first four pages are not tested at all, and neither the memory under the selft-test ROM. The self-test just waits a while and then marks the block as "ok". Also, the self test tests the RAM block-wise, though the way how the memory is organized in the XL is that every memory chip covers a single bit of the entire 64K memory - thus, if a single memory chip is corrupt, all blocks will show up as corrupt.

 

Anyhow, if this is uT memory - try to get rid of it and replace it. This is "known bad" RAM and they fail often and frequently.

[Rybags]

It's not totally useless.

The pattern of errors can potentially indicate what's failing, e.g. actual Ram or select logic.

Though it is pretty funny that they fake part of it - would have been fairly easy to at least test the memory under the 2K Rom.

[WOPRpwJOSHUA]

13 hours ago, Beeblebrox said:

@WOPRpwJOSHUA  so I downloaded your image files and had a look.

 

Good news is you have a rev d 800xl board. Ntsc. 

 

So a rambo xl upgrade will work. It's fairly straightforward to install, but involves socketing ram and replacing with the 256k chips, socketing the upper 74ls158 chip, which the rambo xl board goes in, and also socketing the pia 6520 chip far right of the board. Then a few dupont wires. 

 

See here:

https://forums.atariage.com/topic/351328-rambo-800xl-sm-version/?do=findComment&comment=5310851

I am in the UK and get this premade rambo xl board:

 

https://www.ebay.co.uk/itm/266673794264

 

.. And these 256k chips:

8 x HM51256LP-15 Fast Page DRAM 256K X 1 150ns CMOS 16-Pin DIP

https://www.ebay.co.uk/itm/273100954587?

 

Or there are PBI plugins options for ram upgrades which are plug and okay:

https://forums.atariage.com/topic/336161-320k-parallel-port-ram-upgrade-for-600xl-800xl/?do=findComment&comment=5252720

To buy here:

https://www.tindie.com/products/5cfab/320k-memory-upgrade-for-the-atari-xl-computers/

 

You'll also likely wish to hook up chroma to use svideo,  which is a superior video output on the 800xl, but doesn't come ready from factory. A simple wire with a 100ohm resistor in it, hooked up to the chroma pin 5 on the din5:

 

https://forums.atariage.com/topic/350787-gifting-a-new-build-of-the-800xl/?do=findComment&comment=5265009

 

 

This old image I quickly found shows topside of the board, but you can do this on the underside, just don't forget the 100ohm resistor and heatshrink :

 

 

@Beeblebrox, thanks for the detail/images on the Rambo and Svideo mods - I'll order the 2 sockets for 74ls158 and PIA 6520, that should stage up nicely after I get the 256 ram+sockets installed and the machine checks out. Speaking of, I should start thinking about what to have on hand to check general 'stock' functionality after ram replacement; I've planned on a multicart, would anything else be more useful/necessary to check out ports/etc. beyond metering port connectors? 

Once confident it's typical, I'll start the mods, so far: Rambo, Svideo, ...). I'll try and source from your Rambo link. 

 

[WOPRpwJOSHUA]

14 hours ago, aeberbach said:

Just one caution on those precision aka machined sockets - when they are in, they are not coming out. Conventional sockets and ICs I can remove easily with the desoldering pump - they come free every time, 2 minutes work for 40 pins. The round pin sockets sit right on top of the holes and do not leave any room for air, so the solder can’t be sucked out neatly. Flat pins do leave room for air and the FR310 can suck all the solder right out of there.

 

i found this out the hard way yesterday. I had an 800XL with no sockets where I desoldered everything and socketed it all with my new 40-pin “precision” sockets. Then after just a few insertions noticed that chips were practically falling out and that I had been a complete idiot buying from eBay rather than brand-name sockets from an actual electronics distributor. None of the sockets came loose with the desoldering pump. All needed to be cut with a dremel wheel and each pin removed individually. Out of 200 holes I was lucky only to have to repair two traces, but the machine is now working again and 20 “precision” 40-pin sockets (or their component parts) are now in the bin. I’m buying a stock of AMP sockets.

Thanks @aeberbach, I ordered dual wipe TE Connectivity from Jameco along w/the ram, so I should be good. Def good to know, will keep in mind if/when I ever installs the machined type.