Atari XEGS with SAVO (Saturn Atari Video Output), TK-II, Ultimate 1MB, VBXE and PokeyMAX

[@flashjazzcat]

I ended up boring out the RF modulator hole in the 800XL's casing as well so that the SAVO connector could push home far enough to properly connect with the socket. Since not having to drill the case in any way shape or form is a central part of SAVO's mission statement, this represents a bit of a snag.

[@BruceEverett]

Ohhh. You said "Savo". I haven't had my coffee yet and for a moment I thought you said "Savile". I'd have been happy to see jail bars on Savile.

[@flashjazzcat]

I had a light-hearted sequence in which Sir Les Patterson explains that SAVO was named after the Australian slang for 'This afternoon' - s'arvo. Couldn't get it quite right, though, so I abandoned it.

[@jfloydsea]

Another great Atari video! I just rescued my childhood XEGS from my parent's garage. Well, minus the light gun, figures! It needs cleaning bad but is otherwise in good condition. Not sure how I'll upgrade it yet, I haven't even power tested it.

[@waltciii3]

After a few months of using these in the US, I just use 3rd party Saturn cables. One Saturn to HDMI (with audio) and another analog Saturn to S-video or Composite with Audio. SAVO works well on NTSC 600XLs without monitor ports ( I just don't use the Scart cable). We can get plenty of Saturn compatible retro cables locally in North America. PS I open up the case opening to ~13mm to allow the cable to plug in well. PPS we could just get a Saturn female connector and solder directly, but some of us aren't ready for that. We will spend +20 more for a breakout board.

[@retrorev]

I grabbed one of the very early XL versions of SAVO and dropped it into an 800XL with VBXE. I wasn’t blown away by the image quality afterwards. Saw exactly the same banding and ghosting as you saw. Piotr was very helpful and suggested a few things to try, and even offered to replace the SAVO board. I did manage to improve things a little (mainly by sorting a questionable joint on my VBXE install) and now on the Scart input on my CM8833 it looks pretty good, but on an LCD TV the banding and ghosting is still very noticeable. When I have time I think I’ll switch over to a DIN 13 as I already have a Cool Novelties cable on hand.

[@flashjazzcat]

That most interesting Paul. I know Piotr is genuinely interested in attaining the best possible video quality, but as you say: the LCDs are as a general rule a lot less forgiving of vintage analogue video signals than the old CRTs. My recent attempts to come up with the 'ideal' DIN13 to SCART cable have been quite dogged too, but it seems to be more a case of luck than judgement as far as I can tell. :)

[@fragalot]

I think the auto repeat on the keys is due to the Atari expects to see physical switch being closed as a key is pressed since the keyboard is physically connected to the logic of the Atari's POKEY processor. PC keyboards are their own self-contained computers with a serial-like port sending data, and not opening/closing circuits that's in a grid array. PC Keyboards have their own repeating "rapid fire" routine when a key when it's held down, and the Atari itself has it's own internal "rapid fire" routine of doing the same thing, So I think the timing of both is interfering with each other so you'll get a stuttering effect, and double keystrokes, and probably missed keystrokes.

[@flashjazzcat]

The TK-II GS emits nothing but a simulation of the signal POKEY (or PokeyMAX in this case) would normally receive from the Atari keyboard matrix when scanning the keyboard. The problem is actually down to a timing issue caused by having two microcontrollers - one at either end of the transaction (one doing the keyboard scanning, and one simultating the keyboard matrix). Foft implies that one or the other gets out of sync, thereby messing up the keyboard scanning on KR1 and KR2. See 17:10

[@fragalot]

@@flashjazzcat Oooh i didn't realize you were using a different POKEY chip. But it sure did feel like it was some sort of conflict/interferance.

[@flashjazzcat]

@@fragalot Yeah, but on reflection I think your initial appraisal was on the right lines anyway. I didn't realise until I did some reading later on that PS/2 keyboards do indeed re-issue the same key code with regularity when the key is held down (rather than just perpertually asserting a key down until the key is released).

[@waltciii3]

I am considering this however, you're right I would want the SAVO board. In the US I couldn't use the SCART cable, I would instead get a direct Saturn to HDMI adapter off Amazon. I really wish the VBXE output was as simple as the Sophia 2.

[@flashjazzcat]

Saturn to HDMI adapter could be a nice game-changer with SAVO. I need to investigate this. Thanks!

[@andrewclegg9501]

I've got a RGC Saturn cable, there's no caps in it. If the VBXE has caps on its own RGB outputs then the effective value of the caps in cable is halved, which will screw with frequencies filtered by the 75 ohm resistors to ground on the RGB input lines of the monitor. I reckon the "improvement" to jailbars is actually just blurring them. Try removing the caps in the supplied cable.

[@flashjazzcat]

Good call - many thanks. Maybe those Saturn cables I couldn't find a way into lack the caps as well.

[@andrewclegg9501]

Multimeter

[@flashjazzcat]

@@andrewclegg9501 Absolutely.

[@grahamrolle3923]

Hi FJC If the screen of the cable is connected at one end (i.e.) in the DIN plug it will still act as a screen. it's not unusual for communication equipment to connect the screen only at the transmit end, often with a cap to ground.. thinking of a bi directional system its revered to the equipment sending you something connect the screen but disconnected or cap at 'your end' the idea is to stop ground loops but works as well in one direction.. (not the group) as it's still held to gound at one end not disconnected entirely. (unless there is no connection to ground within the DIN of course, think you said it was..

[@flashjazzcat]

Good points, but the salient point about the Saturn cable is that there appears to be no screen at all (it seems that the chassis at the DIN end is connected to the GND wire connected to the six or seven ground pins on the SCART connector). Certainly when buying SCART connectors for the purpose of constructing cables from scratch, there's some variance in design: some have a ground strap connected to the chassis via a tab, others lack this entirely. The CoolNovelties SCART cable connects the shield to the chassis at both ends as I described, but it's obvious that the Saturn cable - by design - does not, and utilises the chassis as GND. This is the only way to get ten signals through a ten-pin connector. I'm sure that this arrangement would work fine if that GND wire in the Saturn cable were a copper shield instead of a single strand of insulated wire.

[@charlesdorval394]

Not only they force you to buy a cable, but one that doesn't even fit? ... Wow. And charge you for a proper cable? This is ridiculous on a whole new level.

[@flashjazzcat]

I've come to 'not mind' SAVO, since it actually saves me a bit of work, but by its very nature, access to the connector isn't ideal. So the shroud on the cable's connector needs to be trimmed back, and then it's kind of OK - but not great. The boards should definitely be available without the cable, meanwhile, and I would expect to pay no more than a tenner for it.

[@waltciii3]

Maybe a TK-II-Stereo using dual pokey would have been a better solution than a Pokeymax with a separate TK-II. Good to know the incompatibility between TK-II and Pokeymax though. I wonder if the USB AKI by Candle has the same issue...

[@flashjazzcat]

I need to dig one out and test it. I suggested a dual Pokey board to the owner but he ultimately didn't consider stereo that big of a deal.

[@MotownBatman]

Always wanted one of these; The Color Scheme was so Damned Ugly! Still want one now @ 40 lol

[@Jimbaloidatron]

With the Savo XE, could the copper just be exposed in the two back corners and then a big blob of solder to the band of exposed ground that runs around the edge of the motherboard where the shield went (maybe with an old, bent, component leg embedded)?

[@flashjazzcat]

Possibly so, yes, although that ground plane on the SAVO is a surprisingly big sinker of heat from the iron (not to mention the ground plane on the motherboard will be sinking heat too). But if you can get enough heat into the joint, that would probably work out well.