So, my RGB Monitor seems close to shot...

[mozartpc27]

Hello All,

So, about six or seven years ago now (wow, I can't believe it's been that long), I bought somebody's used Commodore 128 system on ebay, and it came with an RGB monitor.  When I bought it, I really didn't have a place for it, and so it sat boxed up for a long time.  Then, I moved to where I am now in 2008, and so I got it all out and set it up.  But, when I set it up, I set it up with a television set, rather than with the monitor that came with it, because I also have an old ColecoVision system that can only use an RF-style video output, and that's really only compatible (so far as I know) with the old TV/game switches, which then can be converted to use the coax input on televisions.

Anyway, lately I've been playing around with this Commodore a lot more, as I finally got a converter interface that allows me to make an XM-1541 out of a regular serial cable, and I've used it to download some files I've wanted for a long time.  Now, I could really use the 80-column capabilities of the monitor that came with the 128 when I purchased it.  So, I dug it out, hooked it up, but then sadly discovered that the monitor displays, for lack of a btter term, a lot of "junk" characters (mostly the @ symbol) when it powers on.  It can still be used, sort of, as I can load GEOS, which, when loaded, looks a lot better than the native screen of the 128, but, on the whole, this kind of sucks, because even in GEOS, though there are no junk characters, there are a lot of dots on the screen.

So, I've been looking around trying to find an RGB monitor for slae or something, but, as I might have expected, they appear to be kind of scarce.  So, what are my options if I want 80-column mode available to me in a clean-looking way?  I know you can buy converters, but the ones that I found were $92, plus shipping.  I'd really rather not lay out that kind of money all in the name of resuscitating a 25 year old computer system...

[mozartpc27]

I should add that the monitor I have also has a composite video input (at least, I think it's composite), and supposedly will therefore work with VCRs, etc.  This doesn't seem to help me much, as what I want to use it with is a ColecoVision and the C128 in C64 mode, both of which, I think, have only RF video outs.  When I tried to run the C128 using the video-in on the back of this monitor and a composite video cord running between the monitor and the C128's RF video out port, it didn't work.  I didn't think it would, but I thought I'd give it a shot.

Anyway, this monitor, as I've said, seems kind of coked anyway, so all of this is a mootpoint I guess, but it would be interesting to know if there were some sort of RF-to-composite converter that would allow me to use the monitor and see if it works in 40-column mode.  The weird thing is, I'm pretty sure the previous owner must have been able to use this monitor in 40-column mode with the Commodore, but it's not at all clear to me how they did it, since the monitor's only other video input, besides the RGB input, is a composite input, which the Commodore can't use, to my knowledge.

[RobertB]

...sadly discovered that the monitor displays, for lack of a btter term, a lot of "junk" characters (mostly the @ symbol) when it powers on.  It can still be used, sort of, as I can load GEOS, which, when loaded, looks a lot better than the native screen of the 128, but, on the whole, this kind of sucks, because even in GEOS, though there are no junk characters, there are a lot of dots on the screen.

That sounds like a C128 problem, not a monitor problem.

So, I've been looking around trying to find an RGB monitor for slae or something, but, as I might have expected, they appear to be kind of scarce.

Heh, we have too many RGB monitors sitting in the club storage right now.  Thank goodness that the Vintage Computer Festival is rumored to be coming back to California this year.  If so, we can have a sales table and sell those at $20 a pop.

So, what are my options if I want 80-column mode available to me in a clean-looking way?

To see the image cleanly and without the use of an expensive adapter, then you'd need that RGB monitor.

            Blockparty 2010 on April 16-18,
            Robert Bernardo
            Fresno Commodore User Group
            http://videocam.net.au/fcug
            July 24-25 CommVEx v6 2010 - http://www.commodore.ca/forum
            and click on ComVEX

[RobertB]

...I want to use it with is a ColecoVision and the C128 in C64 mode, both of which, I think, have only RF video outs.

The C128 has a video/audio-out port; if it has an 8-pin socket, then it has separated chroma and luma (think S-video) and composite out; if it has a 5-pin socket, then it has composite out only.

          Blockparty 2010 on April 16-18,
          Robert Bernardo
          Fresno Commodore User Group
          http://videocam.net.au/fcug
          July 24-25 CommVEx v6 2010 - http://www.commodore.ca/forum
          and click on ComVEX

[mozartpc27]

...sadly discovered that the monitor displays, for lack of a btter term, a lot of "junk" characters (mostly the @ symbol) when it powers on.  It can still be used, sort of, as I can load GEOS, which, when loaded, looks a lot better than the native screen of the 128, but, on the whole, this kind of sucks, because even in GEOS, though there are no junk characters, there are a lot of dots on the screen.

That sounds like a C128 problem, not a monitor problem.

I wondered about that myself, because it does seem to be a computer error in some ways.  For example, if I move the cursor over one of those junk "@" characters and attempt to type a letter, I get a different letter than the one I typed.  However, if I move the cursor to a position where only a junk "dot" appears, it types correctly (this is how I am able to load GEOS 2.0, which doesn't self-load on boot-up, as I got it as a disk image from the internet).  But when I use the RF-out to a television, the video works just fine.

So, I've been looking around trying to find an RGB monitor for slae or something, but, as I might have expected, they appear to be kind of scarce.

Heh, we have too many RGB monitors sitting in the club storage right now.  Thank goodness that the Vintage Computer Festival is rumored to be coming back to California this year.  If so, we can have a sales table and sell those at $20 a pop.

See, $20 is more like it.  I'd be willing to spend that to figure out if this is indeed a Commodore problem or a monitor problem.

So, what are my options if I want 80-column mode available to me in a clean-looking way?

To see the image cleanly and without the use of an expensive adapter, then you'd need that RGB monitor.

            Blockparty 2010 on April 16-18,
            Robert Bernardo
            Fresno Commodore User Group
            http://videocam.net.au/fcug
            July 24-25 CommVEx v6 2010 - http://www.commodore.ca/forum
            and click on ComVEX

Ah, well, on the one hand, thank you for the tip, but on the other hand, here's the rub: I am just a lowly graduate student at the moment, and, even at the extraordinarily low prices this group appears to have reserved at the hotel for this convention, I doubt I can afford to go.  I live on the other side of the country, you see (Philadelphia), and so the flight would definitely be on the pricey side.  We're on a tight budget this summer, and I think the wife would not be pleased if I blew this kind of money to go to a convention in California or Las Vega by myself...

[redrumloa]

This certainly sounds like a computer problem, not a monitor problem.

One thought, what are you using for an RGB cable between the 128 and monitor? Does it have all 9 pins or is pin 7 missing?

[mozartpc27]

All 9 appear to be there.

It certainly would be frustrating if I had to buy another C128 unit.

[RobertB]

I live on the other side of the country, you see (Philadelphia), and so the flight would definitely be on the pricey side.

  Though we'd love to have you attend CommVEx, we understand.  Now in your area, the nearest place where you may be able to pick up a monitor is from MARCH (Mid-Atlantic Retro Computer Hobbyists) in New Jersey.  They have on-going events and host the Vintage Computer Festival East (though I don't see one yet for this year).  Contact MARCH v.p. Bill Degnan at billdeg(at)degnanco.com and see what he says.

             Blockparty 2010 on April 16-18,
             Robert Bernardo
             Fresno Commodore User Group
             http://videocam.net.au/fcug
             July 24-25 CommVEx v6 2010 - http://www.commodore.ca/forum
             and click on ComVEX

[redrumloa]

All 9 appear to be there.

That may be the problem? You don't say what brand and model monitor it is. Is it a Commodore monitor? Pin 7 is removed from Commodore RGB cables, because pin 7 is monochrome composite video for the 128 RGBi pinout. On a monitor like the Commodore 1084(d) this shouldn't be a problem, but another brand may be?

[xc8]

Seems like 4416 RAM problem...

Chris

[BigDumbDinosaur]

The presence of all the @'s on the 80 column screen after power on suggests that all the locations in video RAM have $00.  Something is not correctly initializing the display, you have defective video RAM or no font data.  The latter is copied from the character generator ROM at boot time.  I've never heard anything about the CHARROM failing, so video RAM seems more likely to be the trouble.  It does sound as though the VDC is working to some extent, otherwise you'd most likely see a blank screen.

Somewhere around here is a machine language program I wrote that checks to see if you have 16K or 64K of video RAM in the 128.  Although it was not designed to do a detailed video RAM test, you can try running it and see what it reports.  In the process, it may temporarily disrupt the screen but will then call the kernel routine that copies the CHARROM into video RAM.  If you see any screen action please advise what you saw.

You didn't indicate if this is a flat or 128DCR, but in either case, replacement RAM is still available through sources like JAMECO (you can upgrade the flat 128 to 64K in th eprocess).  It's somewhat tricky to replace though.

[mozartpc27]

Wow, I am amazed at all the technical know-how on display here. 

I must admit, I am not really particularly good at that side of these things.  I certainly used to do some programming on my old C64 - but the kind of programming a 13-15 year old does, which is how old I was when I got into it.  Today, I can do most of the basic stuff, and some of the intermediate stuff, that PC Windows computers can do, but I am no software or computer engineer, I haven't used Linux or Unix in years (and when I did use them, it was only on the most rudimentary level), and, in general, I'm probably unlike a lot of the users on this board in terms of my know-how. 

My interest in my Commodore is part nostalgia and part aesthetic; I really don't have much confidence in my ability to open up my 128 and start fiddling with its internal components (especially considering these machines were not meant to have swappable internal stuff).  So, while I appreciate this kind of knowledge and advice, it's going to be a little on the difficult side for me to apply it!

[mozartpc27]

Oh, and let me clarify: I have a standard 128, not a 128D.

Aside from cosmetics, is there any meaningful difference between the 128 and 128D?  Just curious.

[mozartpc27]

All 9 appear to be there.

That may be the problem? You don't say what brand and model monitor it is. Is it a Commodore monitor? Pin 7 is removed from Commodore RGB cables, because pin 7 is monochrome composite video for the 128 RGBi pinout. On a monitor like the Commodore 1084(d) this shouldn't be a problem, but another brand may be?

The monitor is a Sanyo DMC6500.  It came with the computer when I bought the whole system, and it seems clear to me that, at least at one time, this monitor did work perfectly well with this 128.

[mozartpc27]

The presence of all the @'s on the 80 column screen after power on suggests that all the locations in video RAM have $00.  Something is not correctly initializing the display, you have defective video RAM or no font data.  The latter is copied from the character generator ROM at boot time.  I've never heard anything about the CHARROM failing, so video RAM seems more likely to be the trouble.  It does sound as though the VDC is working to some extent, otherwise you'd most likely see a blank screen.

Somewhere around here is a machine language program I wrote that checks to see if you have 16K or 64K of video RAM in the 128.  Although it was not designed to do a detailed video RAM test, you can try running it and see what it reports.  In the process, it may temporarily disrupt the screen but will then call the kernel routine that copies the CHARROM into video RAM.  If you see any screen action please advise what you saw.

You didn't indicate if this is a flat or 128DCR, but in either case, replacement RAM is still available through sources like JAMECO (you can upgrade the flat 128 to 64K in th eprocess).  It's somewhat tricky to replace though.

I am going to see if I can locate that program and run it, at least.

[redrumloa]

The monitor is a Sanyo DMC6500.

Is the RGB cable end on the monitor end a DB9(rectangular 9 pin)? I Googled but did not see a pinout for that monitor online. Pin 7 from on the 128 RGBi is composite video out, which AFAIK is not exactly standard. It may be worth getting a C= specific RGBi cable with pin 7 removed for when you either fix this 128 or get another one.

Aside from cosmetics, is there any meaningful difference between the 128 and 128D?  Just curious.

The 128D has 64K VDC (80 column video mode) RAM where the stock flat 128 only has 16K. If you spend your time mostly in 64 mode, you may never need the extra ram. If you want to make use of some of the few 128 mode programs out there, the extra RAM is very useful.

[mozartpc27]

Thanks for the clarification on the difference between 128 and 128D.  I have played around a little bit with Basic 7.0 in the Commodore 128.  Some day, when I have more time, I probably will try my hand at designing some programs to run on the 128.  For now, I am mostly going to use the Commodore to run GEOS 2.0 out of 128 mode.  I have some games and things, but most of the software I have other than GEOS needs to be run out of 64 mode.

[RobertB]

...is there any meaningful difference between the 128 and 128D?

Other than more video RAM that Redrumloa mentioned, there is no meaningful difference (though the C128DCR does have the Commodore upgrade ROMs).

Back from Blockparty 2010,
Robert Bernardo
Fresno Commodore User Group
http://videocam.net.au/fcug
July 24-25 Commodore Vegas Expo - http://www.commodore.ca/forum
and click on ComVEX