Best options for Commodore 128 video out?

Mike

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I've only ever encountered a Commodore 128 in real life once, when they were brand new and I saw one in a shop when I was about 15 or 16. I had a C64 at the time, and I didn't know why I really wanted it, but I knew I did. Yesterday, I bid on one that showed up on eBay, and I actually won the auction. I'm picking it up in about a week, so I've got some time to set up my desk because it's absolutely going to be sitting next to my main PC for a while.

I already have a C64 setup in good shape, my SD2IEC is going to be very handy still, and I have a nice Commodore 1701 monitor - so I'm all set to get started. I really want to get the 80 column display up in full-colour glory at some point though, so I'm curious about what the current best options are for handling that.

I'm happy to break out a soldering iron, or look at products off the shelf. I think it'd be nice to get it onto a modern monitor, rather than try to find another CRT. What's out there, and what have people done?
 
May 22, 2019
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So the first thing to know is that the Commodore 128 has two video chips.

The VIC-II chip works the same way as the one in the Commodore 64, with composite and Y/C (S-video) output. This is used for 40 column text and graphics. This is connected to the 8-pin DIN port on the back.

The VDC chip is used for 80-column text and is connected to the DE-9 jack on the back. This port uses a TTL RGBI signal, and it also can support monochrome composite output on pin 5. So the 128 can actually use two monitors at the same time, or you can use one monitor and switch back and forth with a switch box or an internal switch in the monitor.

To get video out to a modern TV set or monitor, you're going to need a few things:

The first thing is an S-Video to HDMI or S-Video to VGA converter. These take the separated chroma-luma video from the DIN port and create a video signal a computer monitor or modern TV can use.

The second thing is a CGA to VGA or CGA to HDMI scaler. This usually requires two components: a TTL to analog converter, to turn the RGBI into an analog RGB signal, then a scaler to turn the signal into something an LCD monitor can use.

I invite other people to leave suggestions for products to do the video conversion, but here's what I use:

KanexPro 4K HDMI converter:


This can put out 1080P and 4K video, and it works great on all of the displays I've used it on. It can even handle 50Hz PAL signals, so if you have a European machine, it will still work.

You'll also need a DIN to S-Video cable, like this one:

1563051642599.png

You'll need to Google for that, as they're usually on EBay, and those listings change periodically. (for obvious reasons.) I usually search for Commodore 64 S-Video cable when hunting those down.

For the 80-column display, you can either roll a composite adapter with a male DE-9 plug and an RCA cable, or you can do it right and get a CGA to VGA scaler:

Again, EBay is your friend for the RGBI to VGA digital to analog converter. It looks something like this:
128

That converts the 4 TTL color channels to 3 analog color channels.

Then you need the scaler. Check out this page for more information on that:

129

Personally, I just made a composite cable for the times I use the C128 in 80 column mode.


Finally, This device claims to be a one-stop converter, and may be your best bet for 80-column graphics:
 
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Mike

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Thanks @TomXP411 - I'd forgotten about the MCE2VGA. I remember watching the LGR review of it, and it seemed good but I had no use for it at the time. It's a bit expensive though, so it might have to wait a bit, heh.

I plan to keep my 1701 for most day-to-day use, so I can run my luma/chroma direct into that, I've got cables I've made to adapt to s-video etc as well, so picking up an upscaler for that might not hurt as well. I've solved all my common display problems on that side with my existing C64s, but I have this burning desire to use the 128 as a terminal a bit, do some more BBSing, and 80 columns will be pretty important to really enjoying that.

I've built a couple of wifi modems and had the C64 online but it only really ends up reminding me why I jumped to a PC for that kind of stuff as soon as possible back in the day. That screen resolution just isn't great for taking in a lot of text. Running it in mono via a composite cable might be a good short-term solution, though as I could run both into the 1701 and just switch it between inputs.

Can't wait to get this thing and start playing!
 
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Markeno

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Jul 19, 2019
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I came across this video today actually:

It seems he used a NEC Multisync monitor directly wired to a DB9 with a breakout to a Vga 15pin cable. The Multisync that he had seemed to support the video output. I can't tell if it just managed to work, or if it worked well, I also didn't see if color was working on that. I have a similar Multisync monitor the 60 series, he used a 70 series model though. I was wanting to look into it for my 128. He apparently originally used that cable and specific monitor for some Arcade stuff, as well as an 8088 with CGA output. If you look at his 8088 video you get a quick look at the cable, but he didn't reference how it is wired etc. I planned to review the videos for what information as in them, and maybe then ask him how it is wired up, provided I didn't find it documented somewhere how to do it.


With what I was going to also look at making a Monochrome Composite cable and hooking that up.
 
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May 22, 2019
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If you look at his 8088 video you get a quick look at the cable, but he didn't reference how it is wired etc. I planned to review the videos for what information as in them, and maybe then ask him how it is wired up, provided I didn't find it documented somewhere how to do it.
Around 25:05 he mentions his breakout board. What he's probably built is the same CGA2VGA board as in my above post. I'll go check out his 8080 video to see what he's got there.
 
May 22, 2019
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Okay, he's just wired the cable using a terminal block. No signal converters. So this means the monitor has to be smart enough to handle composite sync and TTL voltages.
 

Markeno

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That is the video that he shows it briefly. What you described is what it seemed to me he was doing.

The 70 Series Multisync he is using says it has :

ANALOG 0.7 Vp-p / 75 Ohms
Separate sync: TTL Level (Positive/ Negative)
Composite sync: TTL Level (Positive/ Negative)
Composite sync on green: (0.3 Vp-p negative, 0.7 Vp-p positive)
:

So I guess it accepts the TTL. He did mention that specific monitor was to support the input properly.

The 60 Series, which I have has a little less detail there, but I expect similar support?:
ANALOG 0.7 Vp-p /75 Ohms
Separate sync:TTL Level (Positive/Negative)
--------------

I take it if the monitor doesn't support TTL levels. Then that is when you need the "CGA2RGB - Digital RGBI to analog RGB" unit "https://gglabs.us/node/2022". Then if it doesn't support 15Khz input, you need the GBS-8200 that then takes the 15Khz to 30Khz? But if the monitor already supported both, you wouldn't need either. If it took 15k then you only need the GGLabs Digital to Analog bit.
 
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Mike

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Thanks for all the info so far, I've got a lot of things to pick up over the coming months to get things just perfect, but I'm going to make a composite cable today to get things rolling. As of yesterday, the computer that's been on my shopping list for 30 years is finally on my desk where it belongs!

151
 

Mike

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Huge success! Used a really cheap composite upscaler I had in a drawer, a few cable ties to hold the thing together, and it's quite readable on my main monitor. It wobbles a bit, it's certainly not perfect, but it'll do the job in the short term.

152153
 
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Markeno

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Looks pretty good. I am going to see if my NEC Multisync can display the 128 output. I'm being a bit slow to get the time to get the proper cable together for it though. Not much time to focus on it between work and the kids.
 
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Mike

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I just found a place 20 minutes away that claims to have a used NEC 70 series monitor in stock, so I might just swing by and grab it and find out once and for all what's going on.

What's not clear from those videos of that guy is whether he's getting any colour signal at all there. Never leaves DOS text mode on his 8088. From what I know of the pinouts, he's most likely just running R,G, B, Hsync, Vsync and ground into the VGA port and ignoring intensity - which is far from a perfect solution but might well work better than just the composite.

EDIT: Well, that was a disappointing trip!
156
 
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Markeno

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Sorry that they weren't open. Ya, I wondered what color he may get out of that cable. I am thinking 8 colors at best.

Well the NEC Multisync LCD1760V I have doesn't work with it, neither does the NEC Accusync LCD72VX. When the Multisync didn't work I figured I would at least try the Accusync.

I made up the cable, like this:
DB9 MaleSignalDB15
1, 2Ground5, 6, 7, 8, 10
3Red1
4Green2
5Blue3
6Intensity (why but I found it saying 9 and tried that)9
7Mono CompositeNC
8H Sync13
9V Sync14

So I expect he probably wasn't using the Intensity, which I take will cause it to only give you 8 color output instead of 16. I don't see what putting it to 9 would do, unless it is going to some sort of additional circuitry that will take it into account. That pinout is for an Ambery adapter though, it may take it into account. Except I read the Ambery solution only gives 8 colors, which would indicate it is not using Intensity.

The results with both of my monitors with that cable is that they they see a signal but say "out of range" and give no display.

I did put in a RCA jack for the Composite Monochrome output, that at least works.

There only seem to be a few monitors that work. I found this list:

Those are models that may potentially work with 15khz. I don't know if some or all may or may not need a "RGBI to VGA digital to analog converter" as well. That one NEC Multisync doesn't seem to need the RGBi to VGA converter, but if it isn't using the Intensity signal, again it would be 8 colors instead of 16 that way, if I understand the function of it properly. It seems people know their relative use and are selling them, but at a fairly high price for such old hardware. While I wouldn't mind paying a fair price for one, I don't feel like paying that kind of money for a rather old LCD that may quit working at any time (or may last another 5-10 years), and then also find out that it is a slightly different model that doesn't work. Still I will keep my eyes open for one that is supposed to work.

--
My next attempt is to do H2Obsession's RGBI to Scart. Then put that to a Scart to HDMI device that I saw Adrian Black use to connect it up to a HDMI capable monitor. I find it sad that the CGA (basically) output of these computers is apparently a Digital signal that must be converted to an Analog VGA standard to reconvert to Digital again. The Scart converter is inplace of a GBS-8200, it is a bit more money, but seemed a better solution to me. I really don't want VGA too badly, might as well go to the more modern output now and it seems to have settings so that it won't always be stretched to full screen. I may look at some other options later on. I would rather build something myself if I can, as that is as much fun for me as anything.
 
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Mike

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Unless there's an undocumented feature in the NEC range to handle intensity, it's got to be an 8-colour output at best. I stepped through the video at the points where he held up his terminal block, and can only count 6 wires coming off it anyway, so I'm assuming RGB for half of them, the two sync signals and ground.
 
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Markeno

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I am going to go forward on the H2Obsession Pull Both circuit and give that a try. I doubt by itself it will work with the NEC Multisync I have, but I figured I can give it a shot. I figure I can make it up with a switching option between H&V Sync and C Sync, in case I do at some point get a monitor or adapter that accepts the H& V Sync. I will make it up to use with the SCART to HDMI converter I ordered, it is the same as the Pull Both for the VGA to the GBS unit as well so it could do either. I have some other projects in progress right now though. I have one I need to get done before giving it a try though, and I am waiting on the SCART cable and converter.
 
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Markeno

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I was tinkering with H2Obsession's RGBI to SCART design this evening. This is something like I plan to try to do up on a breadboard or such to see if it works. It is a hybrid of his designs. I should be able to use it with the GBS units or SCART output, and maybe possibly the proper model of Multisync monitor if I ever end up with one. In a way it is more complicated with the 7400 NAND Gate ic, as that is what I have to work with, but as they want you to properly terminate the 3 spare gates on the XOR gate ic, it isn't that much different. I don't know if the 7400 will work, but I figured I would give it a try. I will modify it for the proper ic if it works out. I put in trim pots paired to the resistors for adjustments within his suggested ranges without risking going too low. I have JP4 to swap between C Sync and H & V Sync mode. The output would got to a VGA style HDDB15 type output. It does require both the DB9 input from the RGBI and a connector to the Din video port, there it grabs 5volts for the IC and the Audio, which then will go to a audio out jack on the unit. There is the "Cvideo" for the monochrome composite output that can be put in as well. I just like messing with this stuff, you can buy a better solution for not a bad price as is listed toward the beginning of this thread (GGLabs solution for example), but I enjoy messing with stuff. It wouldn't have the brown(?) fix etc and that can't be put in, not with my knowledge anyways. It would be sweet using one of those 7400 ICs I have had laying around for the last few decades. I believe they are actually older than the Commodore 128.

165
 
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Markeno

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I have what I need to try it out, now I just need the time to put it together. I don't know when that will be, maybe I'll find time this weekend to do a simplified prototype like H2Obsession's original design, then if that works, I will try the 7400 for sync.
 

CTaddey

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Aug 6, 2019
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Hey guys.
This may sound dumb, but why do we have to go from ttl (digital) to analog to hdmi(digital)??
Can't we just use some hdmi chip and feed it the data from the c128? Granted, we might need an intermediate uC if the hdmi chip is not programmable.
 
May 22, 2019
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Hey guys.
This may sound dumb, but why do we have to go from ttl (digital) to analog to hdmi(digital)??
Can't we just use some hdmi chip and feed it the data from the c128? Granted, we might need an intermediate uC if the hdmi chip is not programmable.
The 128's CGA output is completely different than HDMI, and AFAIK, there are no direct CGA to HDMI converters out there. Everything I know of uses the intermediate step of treating the CGA signal as an analog input, using resistors to feed it to an analog RGB scaler.
 
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Markeno

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Hey guys.
This may sound dumb, but why do we have to go from ttl (digital) to analog to hdmi(digital)??
Can't we just use some hdmi chip and feed it the data from the c128? Granted, we might need an intermediate uC if the hdmi chip is not programmable.
I kind of wondered if there may be a better way to take the Digital RGBI to HDMI modern Digital. I figured the signal differences are to great for a simple solution. RGB is for driving the electron guns in a CRT. I expect modern Digital HDMI/DVI are optimized for LCD technology and don't have that same throwback compatibility?

I have made progress on putting the breadboard prototype together. I am checking and rechecking everything as to hopefully ensure I don't damage the 128 due to a slip up. I really should have just built it up with the minimum circuit. It depends how much time I have this afternoon, I "might" get to test it connected to the SCART to HDMI and hook it to a monitor. I want to test the RGB outputs from it and see if they look like they are operating on my scope. I don't know what I am looking mostly, but I want to check the output levels and that there are signals. It should be .7Volts max for each of them if fully saturated on a full white screen, it will be the commodore startup screen so it won't be near that. Then I need to figure out how to get connected to the SCART cable without enough test clips.

I looked around and found an option for a Brown fix, but it is another IC that I don't have, and I don't quite understand how they are using it. I have some idea, but I need to really look at what it is doing. I think it is injecting a little into the Green output, which pushes the Dark Yellow into a Brown. How to get just enough, I don't know, and I don't know if i can accomplish it in another way with some gates.