A short video showing how I got a nice clean colour VGA output from my Atari ST. You can buy the clear plastic enclosure from here:- arcadeforge.net... The GBS-8220 can be picked up cheaply on AliExpress
19/03/2017 - I did a mod today to add a voltage divider on the combined sync ouput, to reduce the voltage to ~3v. If you produce your own cable like I did, I would do the same thing because the sync level is over 4v which will eventually kill the GBS-8220 if you don't.
I've been fighting with a GBS 8200 to get VGA out of my STFM and have had no luck. I think due to the differences between STs with and without RF modulators.
Interesting board to have a play with. I've seen diagrams that just connect H and V sync together (also in combination with the GBS board), I guess it's worth a try for a cheap and cheerful solution. If you have an STFM or STE you can get composite sync from pin2.
I had seen a few of these in use with not too good a picture. I guess the owners hadn't played with the settings, useful to know you can get good results if you do. One tip, with unused gates, you should only connect the inputs to ground, and leave the outputs floating. It's a 7400, so with both inputs low, it will be trying to drive the output high. It looks like you might have inputs and outputs tied to ground, which can't be good for the chip. If that's the case, you might want to go back and cut the output pins.
Yes, you are absolutely right - whilst I was watching it last night when it was uploading, I said 'Doh - I've probably killed 3 of the gates in the chip'... It dawned on me that because its a NAND, the output will be high and I am pulling it low... It's one of the annotations I need to add today, along with the fact the board saves settings.
Thanks for the video. I was able to get this working because of it. The only thing I did different was that I used one of the gates but did not bother to connect any of the other gates to a common ground. I also used a 9volt battery for power as opposed to the GBS power and the chip does not get hot now. Thanks
+guitarshredderwilly Yes, I've got to do a follow up video - I bodged the wiring (shorting the gate outputs to ground), hence why it was getting hot. The inputs do need to be connected somewhere (either vcc or gnd) or they can oscillate which may affect picture quality. I've also powered mine from the LCD panel itself (saving a power socket).
Hi. Is this hack for an STE or an STF or will work in both? I read that STF does not have an H/V sync but composite one on pin2, in that case, is the 7400 hack still needed? Thanks
Nice video. Subbed. Any chance of a write up of the mods you actually now recommend for this? The annotations seem to indicate you learned lessons after and it would be easier if we had a guide as I'd love to follow this myself... I also found a link for the CFW but it wasn't obvious what it gave you (to me!) shmups.system11.org/viewtopic.php?t=52172
Thanks =D The diagram in the video shows what you need to do (at 18:00) - the only change I made later was to feed the unused inputs (not the outputs) on the 74HC00 to ground. You can leave the unused output pins connected to nothing.
I saw that CFW post earlier but I am not bothered about doing it - for one thing you need a Rasberry Pi all setup and configured correctly and I just cannot be bothered with it lol. It gives a really good picture for me as it is tbh. I think the CFW might fix the minor ghosting / shimmering when using the cursor on the desktop but I can live with it.
Hi, info-coach.fr/atari/hardware/interfaces.php#atari_video_connector seems to suggest an STE already produces a combined H&V sync so presumable circuit NOT needed? But 680 Ohm resistor to bring down voltage still?
I've not tried with hi res! I might do that when I get more time. You can also get some older NEC LCD screens that work with all resolutions I think. There's a thread on AtariAge forum!
I know some LCDs support the horizontal rate, I am hoping some of the generic ones I have do, not gonna try until my FM is tidy again though - it's in a really sorry state, dust bunnies galore, a gallon of distilled water may be in order it's that bad! Not been on AtariAge for years, gonna have a gander me thinks. Probs forgotten my login by now lol. Have a good day fella.
Interesting that you have a v3.0 board which up until now seemed to be the one with the most problems for people, as opposed to the v4.0. This video will be of enormous help to many people.
Yes, I read that the newer 4.0 boards seem better. Maybe I've been lucky here, one thing to note is that the video can vary in quality between different ST motherboard revisions, and the caps on the ST board are a factor as well. Thanks for the nice comments =)
+Naparovitse I've read that people have managed to use them with the Amiga but you need to make a cable and circuit to deal with the sync signal etc. It won't work with the C64 as the C64 outputs either S-Video or Composite, and the GBS requires RGB. If you want to connect the Amiga and C64 to the CRT you should use Scart / RGB leads for Amiga, or composite if the monitor wont support RGB for some reason. With the C64 you need S-Video or Composite support in the monitor or TV.
the artifacts would have to be fixed by a CFW (one is in the works) and you might want to add a 680 ohm dropper on the csync line as 5V exceeds the max input parameter of the TrueView 5725 which is 3.6, otherwise the board isnt too shabby for the price
That's very interesting! I didn't know it used a TrueView chip, and I had no idea it wasn't 5v tolerant on IO. I will revisit this and cut the outputs from the 7400 from GND (see Daves comment above), and I will drop the voltage on the S (C Sync) line. It will be great if a CFW is create for this!!!
GadgetUK164 not sure what that glitching on the bottom is. could be the 1.8 LDO output capacitor which has too low of an esr for that part, the fix is replace with 22u tantalum
Gillian Seed Thanks, I will take a look at that! It only occurs when changing channels or resetting the input system. After changing channels it disappears.
I gave up on the off shelf up scaler I got from eBay. I have a Sony TV that works with the ST over SCART if I want colour low res from a real ST. When I am ST'ing now for colour I use Hatari. I remember talking with Techie Alison about how wonderful the hi-res "picture" was from the ST on a Dell monitor using one of her leads. On Monday we went to Curry's to buy a new washer. Don't get to town very often and so had a look at the big new TVs while we were there. Some of those big curved TV still have SCART! I started to have odd ideas about using ST with OLED curved 55 inch displays.........had to have a lie down when I got home! :)
Yes, I remember Alison spent a bit of time working on VGA out and I do know she made some great cables which were switchable between colour and mono and designed to connect to TVs that supported them. I vaguely remember her finding a Sharp TV or something which supported the ST output really well. Coincidentally I was talking to my friends Colin (Alisons partner) a few weeks ago and his sons TV needed repairing and he had no TV for a week - Colin loaned him that TV that Alison found for the ST VGA - just at the same time I was tinkering with this VGA stuff and I had just re-read Alisons thread that same day. With regards to a big LED TV - I know what you mean! Drooling at the thought of viewing the ST on a 55" screen or something lol.
GadgetUK164 On a 55" you would truly able to see each pixel. Probably from space on a cloudy day! Did you see that pic that was doing the rounds when Apple launched the 5k Retina iMac which showed an original MacPaint screen shot on the new Mac? It was a little oblong in the corner. Amazing really.
LOL!!! Yes, maybe it sounds ideal but it's probably going to ruin the effect! That was one reason I went for a 19" display, just to limit the size, and get a good aspect ratio. It's actually a 5:4 I am using rather than a 4:3 but it looks fine when you alter the width / height to get it looking 4:3.
Those GBS boards are a lovely low-cost way to get RGB onto a VGA monitor. I use mine with my SNES, Megadrive PS1 and Amiga. Instead of having to mess with various sync formats I use SCART cables for each machine - not sure if that's an option for ST. I bought a Sync Strike and connected that to the input of the GBS. Works well except that my GBS doesn't remember settings and likes to default to the wrong options all the time so I have to manually set it to RGBS every time I start up. I also get nasty fuzzy noise on some PAL signals - not a problem for consoles as I usually run them in 60 Hz (which is clean) but most Amiga stuff is in PAL and there I get irritating interference. There was a German forum link about using some tape to reduce the interference with one of the chips to get rid of the noise but my German wasn't good enough to make sense of the forum post and Google Translate didn't help much either.
Anacreon ZA Thanks for the info about the 'tape fix' there! Very interesting, will look into that! They are pretty good as a cheap way to upscale RGB. The Sync Strike is a nice addition as well! I think I will just use an LM1881 to start with and see how that works out.
You put some foil tape, or just aluminium foil on some double-sided tape and cover the center 6cm or so of the back of the board,. This will give enough shielding to avoid most of the signal noise on the boards with the cheaper ram chip. Also, avoid the 'Jammaboards' version, as their custom firmware has added a 55Hz Midway profile, replacing the 50Hz profile used for a lot of PAL retro computers.
GadgetUK164 Keep in mind the additional shielding is to address the 'white specks' problem. The pixel jumping issue around the cursor or moving sprites is from the de-interlacing being applied when not needed. This will eventually be fixed with GBS-Control, the custom firmware project.
Yes, almost definitely - although modern TV's are probably more energy efficient than the TFT LCD display I am using. I was going to mod the LCD to feed a 5v lead out of the back of it - so I can power the board and mount the board on the back of the TFT. That way its off the floor, part of the monitor and doesn't need a separate PSU.
I am still watching the video. You have just mentioned the CRT effect, "If you want it..." I didn't want it back in the day, I am always surprised some want to emulate it today. Good video.
clangerbasher Yeah, I agree - not sure why people want CRT type affect (other than scanlines maybe) but some people do prefer the slightly blurry look. Personally I prefer to see each pixel.
GadgetUK164 It is taking authenticity too far! It was something we had to put with back in the day not liked. It is different to say occasionally using floppies or similar.
