Is this a fault on my 800xl?

[steddyman]

Hi Everyone

 

This is my first new post and it is about the purchase of my first ever Atari. As a kid in the early eighties my dad couldn't afford to buy me an Atari 800 which I would have loved, so he bought me a Commodore 64. I followed that with an Amiga 500 though a few of my friends had the Atari ST.

 

Today I managed to finally get my hands on an Atari 800XL and a few games, and what a lovely machine it is:

 

I do have a couple of questions though which I would really appreciate some advise on. First of all, i've read how the composite output on the 800XL is pretty poor but I am seeing some odd artefacts and I wanted to make sure this normal:

 

If it is, then I assume the mod mentioned on this forum to remove one of the capacitors would make it a lot better. I might go the whole hog and wire up the luminance signal too. Either that or buy a VBXL or SOFIA mod, thought they don't seem easy to get.

 

Next, I am not interested in running demos or setting up a RAMDISK (I have ordered an Ultimate Cart and SDIO2SD). Is there any real point in expanding the memory, say with an U1MB card? I'v read there are only a few (not very good) games that need more than 64k.

 

Finally, given the above lack of interest in demos, are there any other mods that would be really valuable to me?

 

Thanks in advance.

 

PS I make clone Raspberry Pi Cases for Retro computers and the 800XL is next on my list after I finish the C64 and VIC-20. I already have an ST.

Edited April 21, 2017 by steddyman

[+DrVenkman]

First off, congrats on the 800XL!

​Second, yes sadly, that's just the crappy composite on many (most?) 800XL machines. Having done a couple of video mods on my 800XL's, to me the best, fastest "bang for the buck" 800XL video fix is by forum user Bryan (that's his username) called "Quick 800XL Video Fix" or something like that. A forum search will find it. In terms of improvement for the level of effort, you really can't beat it. A full-on video mod like his later "UAV" video boards is about the best video you can get from these machines without major surgery, but I don't think he currently has any of those boards remaning to sell at the moment. You can search for his UAV threads if you want to learn more.

 

Third, re memory upgrades, I adore the U1MB board and plan to buy another one for a second machine soon. In addition to the memory (which is great for a giant, fast ramdisk if nothing else) you get SpartaDOS X (an incredbly full-featured, actively-developed DOS) built into ROM, a real-time clock, 4 different user-flashable OS slots, four different flashable BASIC slots (which can really hold almost any 8K cartridge ROM), and several other excellent features, such as a built-in patch to the serial SIO routines for faster I/O operations. Just a wonderful widget. If your machine is fully socketed, it's a fifteen minute installation and you only solder 4 wires. Not all 800XL's are full socketed, however. Two of mine are, but the most recent one I got has a direct-soldered MMU chip and OS ROM. So to install as U1MB in them, you have to remove those chips, install sockets and them connect the ribbon cables from the U1MB to those sockets. And while I realize you don't want/need the ramdisk, it's useful if you ever plan to do any programming or even just copying disk images without needing to swap disks and such.

 

Anyway, hope this helps with a few of your questions.

[steddyman]

Brilliant. Thanks for the advice. I will check out that video fix thread first of all. As you can probably tell from the Rigol scope behind it, I don't mind a bit of hardware hacking

 

Your reply has fully sold me on the U1MB. I'll check if my chips are socketed tomorrow then order one.

 

Thanks again

Stephen

[+DrVenkman]

Here's the link to that quick 800XL video fix, by the way.

 

http://atariage.com/forums/topic/41580-quick-easy-video-upgrade-for-800xl/

 

Here is Bryan's latest video mod, the UAV Rev D. I have two of the earlier Rev C boards, which are great, and one of these Rev D boards which is currently in my daily-driver 800XL, which is even better. I think all of these are sold or spoken for, but he may build more or an even further-improved version in the future. But the threads are worth reading to learn more about the XL video circuits, their flaws and how they can be compensated for or improved upon.

 

http://atariage.com/forums/topic/260267-the-uav-rev-d-video-upgrade-thread/

 

http://atariage.com/forums/topic/246613-new-video-upgrade-coming-soon/

[Stefan Both]

Dear steddyman,

 

I fully agree with Dr. Venkmans suggestion.

 

I'm also a late beginner with the 8bit ataris.

At the beginning, I was a bit confused with the modding instructions of the U1mb. After solving

that, I had still some questions and it tooked me a while to figure out what kind of setup is the

most usefull for me...

but, it's just in the beginning.

 

It is the most useful item for the atari!!!

[steddyman]

Thanks Guys

 

Unfortunately my board appears to be an 800XLF PAL with a Freddie chip and none of those instructions seem applicable.

 

Also, only the GTIA is socketed, so upgrades are going to be rather daunting for me

[Rybags]

If it's an 800XL with Freddie then it's fairly rare and of collectable value above a normal machine - you could probably get someone to swap a working standard 800XL for it.

[gilsaluki]

I am probably wrong, but isn't the 800XL with a FREDDIE really an 800XE (rare, small release)?

[steddyman]

No. It is a revision R3 PAL board. It is marked on the computer as an 800XL and on the motherboard as an 800XLF.

[Kyle22]

So, de-solder the MMU and OS ROM and install sockets and a U1M.

 

Why wouldn't it work in an 800XLF?

[Joey Z]

So, de-solder the MMU and OS ROM and install sockets and a U1M.

 

Why wouldn't it work in an 800XLF?

I think the point is that he can't install the sockets. He was hoping the machine was socketed, because it's easy to tack on a few wires, but more difficult to remove a couple DIP chips without damaging the board

[steddyman]

Still video is my main priority to resolve and looks terrible. Someone has suggested to me that s-video is already connected on the XLF so I will get a cable and try that first.

[Rybags]

S-video is preferable anyway, that composite pic of yours looks like RF where the TV is off the channel to the point of breaking up.

If you don't have S-Video by default it's a wire + resistor job which doesn't need a whole lot of skill.

[steddyman]

Thanks Rybags

 

I was directed to this page for the instructions on soldering S-Video:

http://biosrhythm.com/?p=1002

 

However fI cannot find C54 or R67/8 anywhere on my board because of it being so different:

[Rybags]

I think there's a page that refers to the chroma addition in it's simplest form, ie no other modification or removals. Probably long gone though.

 

I can't easily refer to my machine as it's got VBXE, Ultimate 1 Meg hanging off it and I can't just turn the motherboard upside down to see where it goes.

[steddyman]

It wouldn't help anyway Rybags unless yours is an 800XLF.

[Rybags]

The thought I had was identify where in the circuit the connections are then extrapolate that to an XLF.

 

http://ftp.pigwa.net/stuff/mirror/jsobola/

 

Scroll down that page, you can download the zipped schematic packages for various Atari equipment.

[steddyman]

Perfect, thanks. That is exactly what i've been looking for.

 

My reading of the schematics is for the 800XL the above guide says lift the right side of C54 (connects to Composite signal) and wire signal from left side of R67 (connects to R68). That is covered in diagram 800XL3.PCX on the right hand side.

 

The 800XLF has an almost identical schematic called 800XLF3.PCX and fortunately the output stage to the monitor appears the same but the component numbers are all different. My reading of the diagram is I should lift the right side of C46 and solder a wire to the left side of R45 (connects to R59). It also confirms that the chrominance signal is not currently connected so I would need to do the mod.

 

Does anyone else concur?

[steddyman]

Quick update on this one.

 

Today my Atari 800 S-Video cable arrived and before I went to the trouble of soldering a jumper wire, I thought I would try it first. To my surprise it worked without any modification on the 800XLF showing colour just fine. There are no jumper wires at all on the board of the 800XLF so this is as it was built. Great news.

 

The picture is definitely much better than it was on Composite, but you still have these horrible chequered patterns all the way through the picture. Is this normal?

 

[+DrVenkman]

What kind of screen are you using as a display? My CRTs look nothing like that with S-video.

 

 

[Joey Z]

Yes, some TV's just suck with atari's no matter what you do, can you try another? This should really probably be the first comment any time a 'bad video quality' question comes up. Some TVs flat out refuse to work with ataris.

[steddyman]

I'm using it with a Dell 24" LCD that is about 8 years old but very good quality. It has Composite, S-Video and Component in addition to VGA, DVI and HDMI.

 

I've also tried it via a cheapish ($30) composite to HDMI converter to the same monitor. Similar results.

Edited April 26, 2017 by steddyman

[Rybags]

I should have asked that before - it would seem that lots of modern LCD TVs do a poor job of rendering the Atari and other old computer/console's video.

 

It seems like every imperfection gets amplified, whereas on older CRTs they'd be barely noticable in some cases.

[Sugarland]

Yes to me it looks like your display is the cause of that issue, not the 800XLF. The Dell 20" 4:3 screens from around 2006-2007 are quite good. Ironically, the earlier LCD screens tend to pay more attention to composite/s-video input since everything was still in early transition to HD. My Vizio from 2015 gives a very bad composite picture with flickering pixels. I don't think anyone makes s-video as an input option any longer. That stopped a couple years ago.

 

Yes the latest run of 800XL's have the chroma wired. You've got a great 800XL there. I see it has a good keyboard type too! Be glad. Treat it well! =)

Edited April 27, 2017 by Sugarland

[steddyman]

I promise i'll look after it Sugarland

 

I just found my old Sony Trinitron 14" TV in the garage that has a SCART (that even supports RGB). I'll give that a try once i've let it acclimatise to the house