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Commodore 128 80 Column not working.

M

Max IBM5150

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Oct 12, 2011
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33
Location
Louisiana, United States
I just bought and cleaned up a Commodore 128 that looked like it came out of a barn and had been there for awhile. (It had pine neatles and spider nests in it) So after I finished cleaning it up I hooked it up to a TV via the RF modulator and it worked fine. But today I decided to test out the 80-column display with my IBM 4863 ( Display made for the PCjr) with an adaptor and nothing was displayed on the screen after pressing the 40/80 display on the 128 and resetting the computer. The 40 column screen went blank (with the green border) and the 80 column screen was blank like it was'nt getting a video signal at all, it just stayed white.It seemed to fliker when I reset the computer. The computer still responds because when I type GO 64 it goes int c64 mode with the 40-column screen and works fine.

Does anyone know what might be wrong here? The 4863 display does work. Mabye the VDC is dead or the adaptor for the 4863 may be the issue.

Or would getting a Commodore 1902 Display solve this problem?

Any help would be appreciated.

Thanks,
Max
 
Have you tried re-seating the chips on the board? Gently but firmly press them back into the sockets; if you hear a lot of crunching and they go very far back in, they'd crept partway out.

The specific display shouldn't make a difference; the VDC's default settings work fine on every RGBI display I've tried. The Commodore monitors that can take both composite and RGBI are nice for the 128, but not necessary.
 
Easiest test is to boot in 128 mode, at 40 columns, and type:

GRAPHIC 5,1

That will switch to 80 column mode. If you see the READY prompt on your 80 column monitor, then the VDC is fine, and it might be something else.

I had a 128D where 80 column mode was sporadic. Sometimes it would boot into 80 column mode, other times it would boot in 40 column mode, regardless of the 40/80 switch. Turns out it was actually the keyswitch itself that was bad.
 
Another test of the vdc is making a composite adapter, pins 7 (Signal) and 1 (GND). This will give you a black and white pic on a composite monitor.

Later,
dabone
 
It turns out that the adaptor I was using was bad, some of the contacts were away from the connector. I tried to repair it and I got the READY prompt on the 80-column display, but everything was red I tried to change the text color and it wouldnt display the new color.

I am guessing that the other connections are beyond fixing and I was able to just get the red+sync signals.

Would it be safe to say that the VDC is fine and attribute the red text to the bad adaptor?
 
It is probably completely unrelated, but when I made my first cable to connect a BBC Micro to a 1084 in RGBI mode, I only got red text on a fading screen. In my case, I think the 1084 is having issues with RGBI but I should test with e.g. one of my C128's to be sure. I ended up making a TTL to analog cable with resistor dividers and used the analog mode of my 1084 to get a proper display.
 
Thanks for everyone for their input, I will probibly get an 1902 in order to get all graphics modes in 1 display and use the Y/C split to take adavantage of the best graphics avlable.

I just heard that the 1902 has a DIN port on it too. Is that for audio / 40 column video and is the quallity any different from the Y/C split? I don't own one and I can't find anything about this port after I ran across this cable that said you could directly connect the computer without RCA jacks.

I also found this site:

http://c64tapes.org/

It has many cassette tape programs for the C64 but I dont know if they are PAL or NTSC. I know that there was many problems with the different types of C64 because of refresh rate and differences in the 6510. Did they do anything to fix these problems in the 128's 8502 and VIC ll+?
 
Pick up a 1084s if you can, it does all the 1902 does, plus stereo audio, and analog rgb. It's what I have on my 128.

And no, the 128 acts just like a 64 in pal vs ntsc, they have different resolutions and scan rates, and a pal/ntsc computer are actually clocked a little differently.

Later,
dabone
 
Not to mention 1084's tend to be much easier to find and cheaper on top of that. Don't get me wrong - the 170x, 180x and 190x are great displays but sometimes more for the connesoir or die-hard collector than for casual use. Some people claim the display is finer and sharper on the earlier displays than on the later 108x monitors, but I don't know how well that holds true.
 
Thank you for the recommendation. I knew that the 1040s was for the Amiga but I had not looked much into it. I'll see if I can find one.

But if the 1084s has analog RGB, wouldn't it be incompatable with RGBI? Or is there an RGBI connection on it too?

Has anybody has any experence with .tap files and audiotap? I cant get it to work. I downloaded the .tap files and audiotap and converted the .tap file into a .wav file and connected my tape recorder to the computer with a audio cable. It seems to record fine but when I try to load it the screen blanks out (to find the header and name of the program) but then it returns a READY prompt and when I type run it just gives me another READY prompt. Or sometimes it tells me Out of memory error and then gives me a READY prompt. Or it might even flash the screen so I see the text on the screen where I typed the LOAD command. If it does this, I have to reset the computer after about 5-10 minutes of it doing this.

I know the Datasette works because I tested it like it said in the manual and I also ran a degauss tape through it .

I checked the level on the recorder and it it seems just as loud as the test program I wrote.
 
Double-check before you shell out for one, because it's my understanding that Commodore used a lot of different setups and sold them all as the 1084, but mine has a switch for analog RGB or RGBI.
 
There were lots of different variants of the 1084, but all of them could do composite, RGBI for the 128 and PC clones, and RGBA for Amiga. So could the 2002 and the Amiga-branded 1080, but the 1084 will be easier to find because it was in production a lot longer.
 
Usually there are two switches on the back side to select CVBS/RGB and RGBI/RGBA. The 1084S usually has a DE9 that supports both analog and TTL mode. Earlier 1084's might have a 6-pin DIN + 8-pin DIN for the respective inputs, or here in Europe some models even have SCART connector for analog RGB + composite video.

Regarding your tape problems, it could be that the azimuth angle on your regular tape recorder and the Datasette are not the same. On the Datasette, there often is a small hole right above the R/W head. By carefully adjusting the screw underneath, in steps of 1/8 rotation or so, you can align it differently. I suppose Audiotap produces a WAV with enough volume and that when you record it to tape, you don't get it downmixed or clipped. Otherwise that is a very common problem, playing back data tapes at a too low volume on those systems which take a regular tape recorder.
 
Well, it turns out that that the datassette worked when I switched .tap to .wav converters. The cassette recorder used is a Marantz PMD222, so I shouldnt have any problems with that.

When I switched converters, the games loaded up. But they run too fast, have the wrong colors, or freeze or just not even do anything. I beleve that this is because I live in the USA and have a NTSC machine, and these tape images are coded for PAL machines. I have heard of something called NTSC fixing PAL programs to run correctly on NTSC machines, but I don't know anyting about it except for it somehow takes code out of the extra 32 raster lines that NTSC machines don't have and makes the game run at the right speed too.

Has anyone developed a soloution for this problem? Mabye some kind of utility/program to load up a PAL game and make it work on an NTSC machine?
 
Wrong colours? That sounds very strange for being a Commodore computer. Too fast or out of sync I can understand. I haven't investigated how many games are archived in PAL or NTSC versions, but I think only the most basic games would be possible to fix with a generic converting program. Anything that counts raster lines and/or cycles will need reprogramming, which actually happened quite a lot.
 
I found out the wrong colors was a loose video cable on the back of the TV, so that is fixed.

Was the Commodore 64/128 more popular in England than the US? Or is it that most of the tape software was sold in England.

Would it be easier to find 1571 Disk images in NTSC format because disk drives were used more in the US?

Or would it be better to learn to reprogram these programs for NTSC?
 
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