SVIDEO mod for (rare?) Atari 800XL Rev. 3 board

[naujoks]

I'm trying to do an svideo mod on my 800XL, but my board revision (rev. 3, 9/84) has a very different video out section (see pic).

Does anyone know how to do the svid mod on this revision? I'd just want to do the "quick and dirty" mod that runs one wire to pin 5 of the socket, which gives me a great picture on my Sony PVM with my other Ataris.

To matters worse, most part names are printed UNDER the respective parts, so even if the components have the same name, it would still be difficult to locate them.

[+x=usr(1536)]

Just to clarify: is this a PAL machine?

 

I'm guessing that it is from the German-language newspaper it's sitting on (and lack of channel switch, etc.), but good to have confirmation 

[naujoks]

Yes, it's PAL (nice deduction!).

[flashjazzcat]

This is an 800XLF (with Freddie), and unless I'm mistaken (which is entirely possible), this board type has chroma hooked up already.

 

Edited February 19, 2023 by flashjazzcat

[naujoks]

On my monitor I'm only getting a b/w picture though (svideo input).

[Rybags]

800xl.zip800xlf.zip

 

The Sobola schematics though some apparently have errors.

Your machine would be Freddy equipped (has 6 x 40 pin main ICs) aka 800XLF (not an official name)

 

If it is the case that you need to do the mod, then you might be able to trace the required pickoff point to attach the chroma if the component names are different.

I did the mod on my non-Freddy 800XL but that was probably 15 years ago.

 

[flashjazzcat]

8 minutes ago, naujoks said:

On my monitor I'm only getting a b/w picture though (svideo input).

Chroma is most certainly connected, as demonstrated by this photo of the underside of another XLF motherboard:

(From this post.)

 

Perhaps there is some secondary issue at play, such the colour pot requiring adjustment.

 

EDIT: board bears model name 'XLF' on underside next to PBI connector.

Edited February 19, 2023 by flashjazzcat

[naujoks]

I can confirm that pin 5 of the video out is indeed connected to something.

Does the cable that I use on my other 800XLs need to be wired up differently, maybe?

[flashjazzcat]

No, same cable should work. Now I think back, the last XLF I worked on here had colour over s-video straight out of the box using my standard cable.

 

[naujoks]

Playing with the pot on the board gives me a bit of a blue picture at one setting, but that colour doesn't have anything to do with the real colour, so just some weird artefact, I think.

I have no experience with composite video. Should I be getting a picture by hooking up a cinch cable from the connector on the board to the monitor? If so, there's something wrong with that as well, as I'm only getting a black screen.

[flashjazzcat]

I would expect GND on the composite cable to require connection as well, but it should work fine. The colour circuit is next to the Y2 crystal, so if something's wrong with the board, I would guess around there. I have experienced an XLF with a dead crystal (as unusual as this is).

Edited February 19, 2023 by flashjazzcat

[naujoks]

I just connected my other 800XL via cinch (called TV on the computer) and the monitor, and that gives me a black screen as well.

[flashjazzcat]

Oh - I misunderstood you before. I think you have the RCA cable connected to the RF modulator. That won't give you a composite picture (you need to tune the TV to the modulated video signal).

 

[naujoks]

Yes, I don't have a TV, it's a PVM monitor.

I just checked the Y2 crystal with the scope and couldn't get a clean reading at all, so maybe that's the fault. If I were to take out the crystal altogether, should the picture remain the same as it is?

[flashjazzcat]

If you remove Y2, you'll lose colour on composite and s-video. Nothing else.

[Beeblebrox]

Just catching up with this thread. Nice 800XLF board there.

 

As stated above XLF's will have colour S-video working so normally no need to do the mod to hook up chroma. I've had a good few 800XLFs through my hands and all work with S-video colour out the box.

 

Just so I am getting this correctly having skim read the above posts - you normally hook your other Atari's to your PVM monitor via the RF and a single rca cable? No need to tune (as of course it isn't TV) - it just works? (I'm not familair with PVM).

 

For S-video you would be hooking up a display with an S-video input via the 800XLF's Din5. This will work on 800XLFs, (stock 800XL's and 600XLs which have had chroma hooked up), and then the 800 and XE lines out the box. (The 800 and XE have chorma hooked up from factory). 

 

So as stated plugging via the RF with an RCA isn't going to work.

 

Request: Can you post some images of where you are plugging the cable(s) in on the 800XLF as well as some pics of your PVM inputs, cables used and anything else. For me I'd need to see it as struggling a bit to understand the setup you have there.

 

Not being familiar with PVM displays do you have to cycle through inputs at all?  Reason I ask is that my 10" CRT monitor has various inpurts including an AV1 and AV!-S, (where if I am hooking my A8s to it via S-video I need to make sure it is on the AV1-S input to get colour.)

 

I am just wondering if this is all down to a misunderstanding as to where to plug and which cables to use. (Again without some images I can't really get a handle on it).

[naujoks]

I don't have crystals of the precise value at hand, but just for giggles I took the crystal of an Atari Portfolio, which is 4MHz sometihng.

The picture doesn't change at all, but when I measure this crystal with the scope, it showed the same erratic reading as the original crystal (incidentally I only get a reading at one of the contacts).

I don't know much about crystals, but even if this crystal isn't the exact same one as the original one, shouldn't I get the MHz shown that this crystal has?

[naujoks]

I'm using a cable which I put together myself, 5 pin on the Atari side, SVIDEO plug on the monitor's side. It's worked well with all 800XLs and 800s I've had.

[Beeblebrox]

gotcha

 

And the cable still works at this current moment with your other 800XL? Just so we know the cable is still functioning and isn't causing the issue.

 

Do you have the pinout you used to make it?

 

Also might be worth checking whether the transitors in the video circuit are all functioning.

[naujoks]

Yes, I tested it with my other 800XL. Svideo only has 4 pins, so it's not difficult to get it right.

I will check the components around the crystal since I'm not getting the right measurements there.

[naujoks]

So it turned out to be a bad capacitor at C304 (incidentally, the markings on my PCB don't correspond at all with the provided schematics), which sits right under der FREDDIE, to the right of the 14.xxx MHz crystal - surprising that it should be within that area.

I discovered it following this thread: 

I would have had a hard time finding this myself, since my crappy component tester doesn't even read small pF values. I used 22pF, didn't have 18pF at hand. I needed to set the colour pot almost all the way clockwise, but regardless, I have colour, and it's such a glorious picture on those Sony PVMs!