Topic: 128D without keyboard keeps showing a green screen.... some help needed

[caren103]

Hi,

I have not owned a Commodore computer until now.

I bought a C64 through Ebay, and the seller included a 128D without keyboard almost for free.

The C64 seems to work OK, but when I start the 128D ( without keyboard ) it only shows at the screen a green border, and in the "inside" of the borders a series of characters.

As I am a newbie, I don't know if this is normal if a keyboard is not plugged to the 128D, or the machine has any trouble.

When I push the reset button, the 128D resets, but the resulting screen after reset is the same ( green borders, and so on ).

I've inspected the mainboard, but I have not detected visually anything strange.

Might you please tell me whay you think ?

Thanks !!!

[Blacklord]

Check if the 40/80 key is down.

[caren103]

Check if the 40/80 key is down.

No, the key can't be down, as I have no keyboard.

I plug in the 128D WITHOUT keyboard, as I don't have it.

So I ask if the "green" borders screen could be due to NOT having keyboard.

[Mark Smith]

I'll drag my machie out and pull the keyboard connector out and see what happens.

I wonder if it is displaying happily on RGB and the 40 column output just has the green ... you say they are charaters on screen ?  Can you take a picture ?

Mark

[caren103]

Hi Mark.

Thank you for your help.

Now I'm goign to bed ( it's very late here at Spain, and tomorrow I must go to work ).

I'll take a picture and post it as soon as I can.

I connect the C128D to the CRT TV via the RF output, as I don't have a RGB cable.

The Computer only shows the described "green borders" screen with the garbage of characters "inside"; if I do a reset, after it shows the same screen ( sometimes with a slight variation in the "inside" area ).

Perhaps is that if you don't plug a keyboard, the computer can not start.... but I don't know.

Please, let me know if you do the test.

I'll post my pictures too, so all of you can see what I see.

Good night and thanks !

[RobertB]

The C64 seems to work OK, but when I start the 128D ( without keyboard ) it only shows at the screen a green border, and in the "inside" of the borders a series of characters.

As I am a newbie, I don't know if this is normal if a keyboard is not plugged to the 128D, or the machine has any trouble.

     Without taking out my plastic C128D out of storage and testing it, my metal C128DCR shows a black screen without any characters in both 80-column and 40-column modes when used without a keyboard.

                Truly,
                Robert Bernardo
                Fresno Commodore User Group
                http://videocam.net.au/fcug
                The Other Group of Amigoids
                http://www.calweb.com/~rabel1/
                Southern California Commodore/Amiga Network
                http://www.sccaners.org/

[caren103]

Hi,

Here are the pictures:

- After starting the computer:

- While pushing the RESET button:

- After resseting the C128D:

The "black" areas are an effect of the refreshing from the TV when you take a picture.

Sometimes the characters mess present some kind of variation ( some flashy areas, etc. ).


RobertB, hi, and thanks for your answer; so your C128CDR doesn't show anything more than a black screen if no keyboard is connected... may I ask how can each screen mode be selected without using any keyboard ?

My C128D is from Germany, and the sticker says "C128D"; it is a metal 128D.

[SmallCleverDinosaur]

I bought a C64 through Ebay, and the seller included a 128D without keyboard almost for free.

Even though you didn't get a keyboard, it was still a find since the metalcase C128D is quite rare

Robert B, hi, and thanks for your answer; so your C128CDR doesn't show anything more than a black screen if no keyboard is connected... may I ask how can each screen mode be selected without using any keyboard ?

The 40/80 key on the keyboard is connected directly to one pin on the MMU-circuit. The MMU controls all the memoryconfigurations of the C128. So when the keyboard is absent the MMU will see the 40/80 key as either up or down and select the screens accordingly. This might also be the problem. Since there is no keyboard the MMU-line for the 40/80 key is neither up (high) nor down (low) which may confuse the computer and give you these strange results. Normally, when the keyboard is there and the 40/80 key is pressed at startup or reset, the 80 column screen becomes active and the 40-column screen is empty, i.e with it's grey background and green border. But without the garbage

[caren103]

Thanks a lot... I deduce so that the C128D could be working fine, but it is the non-presence of a keyboard which could be making it present that screen.

I've been recapitulating about all since I started checking the computer, and remebered some facts:

1) The very first times I switched it on, the screen on TV was totally black: signal was received by TV, but all was black.

2) I made some resets, and switched off, wait, switched on, the computer some times.

3) I also tried to connect ( with the C128 switched off, of course ) a ( switched off ) external diskdrive 1541-II, switched the diskdrive on, and after this I switched the Commodore on.

I don't remember if the green screen came after making the "2)" steps, or the "3)" steps.

Is any way of ( without a keyboard ) being able to "tell" something to the computer so I can check if it works OK ? Connecting a joystick, inserting a disk with auto-boot ( I don't now if this exist on Commodore; in fact, I don't even have any 5 !/4 disks, but could get some of them for testings; also, I own a XA1541 device ), etc. .

And, also, were a cheap keyboard could be found ( aside of Ebay ) ?
Obviously, I would prefer to know if the C128D works OK before purchasing anything for it ( it's a difficult economic time here too at Spain, and many companies are closing and thus people loosing their jobs, and well, the company where I work.... it's in great difficulties, so....  )

In any case, is great to now the metal C128D is an interesting item !!! Let's hope it works OK !!!

[Blacklord]

Even though you didn't get a keyboard, it was still a find since the metalcase C128D is quite rare

That probably depends on where you are, they'refairly common here in Oz!

Lance

[SmallCleverDinosaur]

Oh, I didn't know that. I bought one from a guy in Sweden a few years back and when I recevied it I was really surprised, I had never seen a DCR before. Didn't even know it existed

But it's still more uncommon than the plastic version, isn't it?

There is also supposed to exist a flat C128CR, has anyone seen one or has got one?

[Andrew Wiskow]

SmallCleverDinosaur, I've never actually seen a plastic 128D in person.  AFAIK, they were only sold in Europe.  The metal one is the one that was sold in North America.

caren103, you might try inserting a C64 cartridge game into the expansion port and turning it on.  That might force it to start up in 64 mode and launch the game.  That may get something to display on the screen besides garbage.

Unfortunately, you might find it difficult to find someone with a spare 128D keyboard.  The only online store that I know that even has it listed is at http://www.oldsoftware.com/Commodore.html ...  But it says "call or e-mail for availability", so they may or may not even have one.  It wouldn't hurt to ask though...

[SmallCleverDinosaur]

SmallCleverDinosaur, I've never actually seen a plastic 128D in person.  AFAIK, they were only sold in Europe.  The metal one is the one that was sold in North America.

No wonder then, that I had never seen a metal one

caren103, you might try inserting a C64 cartridge game into the expansion port and turning it on.  That might force it to start up in 64 mode and launch the game.  That may get something to display on the screen besides garbage.

That's a good idea The C128 might test the GAME and EXROM lines before it performs keyboardchecks and thus be able to switch to C64 mode.

Unfortunately, you might find it difficult to find someone with a spare 128D keyboard.  The only online store that I know that even has it listed is at http://www.oldsoftware.com/Commodore.html ...  But it says "call or e-mail for availability", so they may or may not even have one.  It wouldn't hurt to ask though...

There are of course alternatives to a real C128 keyboard, i.e using an interface and PC-keyboard instead. But those interfaces are quite expensive if used only as a substitute for a lost keyboard. But as a new and cool piece of technology they are quite nice Look here or here.

[Blacklord]

SmallCleverDinosaur, I've never actually seen a plastic 128D in person.  AFAIK, they were only sold in Europe.  The metal one is the one that was sold in North America.

And Australia too for both versions.

[Andrew Wiskow]

SmallCleverDinosaur, I've never actually seen a plastic 128D in person.  AFAIK, they were only sold in Europe.  The metal one is the one that was sold in North America.

No wonder then, that I had never seen a metal one

Let me rephrase what I said earlier...  The plastic 128D, as far as I know, was only sold in Europe.  The metal one came out later as a "cost reduced" version of the original 128D, and was sold worldwide.  So for those of us in places like North America and Australia, we never saw the plastic one because the metal version is the only one that was sold.

[caren103]

Many thanks for all the info !!!

- I agree: inserting a C64 game cart seems a VERY good idea, at least to try a method to check the C128D. I will look to find somewhere a cart which costs me cheap shipped to Spain.

- I have written to "oldsoftware.com" as suggested, asking about a C128D keyboard. Let's see what they will say.

- Regarding the interfaces PC Keyboard-to-C128D , they seem pretty good items. I'm trying to find its price, etc., to evaluate this option too.

[6502Dude]

While I can not see the screen detail well, the "garbage" appears to be a consistent character or sequence of characters.

This may be caused by open on address lines to character rom (or video memory), defective video memory, or defective video CRT controller chip.

I do not expect lack of keyboard to cause the video illustrated in 2nd image.

[caren103]

I do not expect lack of keyboard to cause the video illustrated in 2nd image.

The screen in 2nd image is what appears while you're pushing the "reset" button ( so, the screen the machine shows while is resseting ); I thought precisely that image was the more "normal" one...

[6502Dude]

I do not expect lack of keyboard to cause the video illustrated in 2nd image.

The screen in 2nd image is what appears while you're pushing the "reset" button ( so, the screen the machine shows while is resseting ); I thought precisely that image was the more "normal" one...

Me bad.
I should have typed "3rd image" which appears to be screen of reverse * characters.

[SmallCleverDinosaur]

- Regarding the interfaces PC Keyboard-to-C128D , they seem pretty good items. I'm trying to find its price, etc., to evaluate this option too.

In october 2008 Josef Soucek of the IDE64 team gave me a price of 56 Euros including shipping within the EU for their interface (this one).

While I can not see the screen detail well, the "garbage" appears to be a consistent character or sequence of characters.

This may be caused by open on address lines to character rom (or video memory), defective video memory, or defective video CRT controller chip.

I do not expect lack of keyboard to cause the video illustrated in 2nd image.

I'm afraid that I have to agree with the 6502Dude, there might be some malfunction with the computer that wouldn't go away even if it had a keyboard attached.

1) The very first times I switched it on, the screen on TV was totally black: signal was received by TV, but all was black.

2) I made some resets, and switched off, wait, switched on, the computer some times.

3) I also tried to connect ( with the C128 switched off, of course ) a ( switched off ) external diskdrive 1541-II, switched the diskdrive on, and after this I switched the Commodore on.

I don't remember if the green screen came after making the "2)" steps, or the "3)" steps.

I suspect you have a cable from the computer to the TV that has a set of smaller cables? The video connector of the C128 consists of these lines:

Lum/Sync
Audio out
Video out
Audio in
Color out
Ground

If you by accident tried to connect your TV set to the wrong signal you might have damaged the computer. It seems that the C128 is very fragile when it comes to this connector. I once tried all the different cables from the connector and connected them one by one to my TV until I got the picture. And then it looked more or less like yours does. That was a plastic C128D and it never worked again

BTW, does anyone know what the "Audio in" signal is used for?

[airship]

The SID chip has an audio in input that can be mixed with SID sounds. It's meant for chaining SIDs together, but it works for any audio input of the correct level. Don't overload it.

[SmallCleverDinosaur]

I should have known Thanks!

[caren103]

- Regarding the interfaces PC Keyboard-to-C128D , they seem pretty good items. I'm trying to find its price, etc., to evaluate this option too.

In october 2008 Josef Soucek of the IDE64 team gave me a price of 56 Euros including shipping within the EU for their interface (this one).

While I can not see the screen detail well, the "garbage" appears to be a consistent character or sequence of characters.

This may be caused by open on address lines to character rom (or video memory), defective video memory, or defective video CRT controller chip.

I do not expect lack of keyboard to cause the video illustrated in 2nd image.

I'm afraid that I have to agree with the 6502Dude, there might be some malfunction with the computer that wouldn't go away even if it had a keyboard attached.

1) The very first times I switched it on, the screen on TV was totally black: signal was received by TV, but all was black.

2) I made some resets, and switched off, wait, switched on, the computer some times.

3) I also tried to connect ( with the C128 switched off, of course ) a ( switched off ) external diskdrive 1541-II, switched the diskdrive on, and after this I switched the Commodore on.

I don't remember if the green screen came after making the "2)" steps, or the "3)" steps.

I suspect you have a cable from the computer to the TV that has a set of smaller cables? The video connector of the C128 consists of these lines:

Lum/Sync
Audio out
Video out
Audio in
Color out
Ground

If you by accident tried to connect your TV set to the wrong signal you might have damaged the computer. It seems that the C128 is very fragile when it comes to this connector. I once tried all the different cables from the connector and connected them one by one to my TV until I got the picture. And then it looked more or less like yours does. That was a plastic C128D and it never worked again

BTW, does anyone know what the "Audio in" signal is used for?

I connected and connect the computer to TV with a RF cable ( and always with computer and TV off when connecting the cable ), throught the RF out connector from the C128D.

What I don't understand is why the first times I started the computer the screen was black, and after some testing, it changed to this... I don't know if the computer came in a configuration to work in 80 columns ( if then is when shows a black screen ) and with the tests it changed to 40 column mode, and showing "something was wrong".... I don't know.

And yes, I agree that something is wrong in the C128D.... I will try nowadays to insert a game cartridge to check what happens.

Anyway, if you are rightn and something about the video memory is damaged, could it be replaced or fixed ?

[Blacklord]

Let me rephrase what I said earlier...  The plastic 128D, as far as I know, was only sold in Europe.  The metal one came out later as a "cost reduced" version of the original 128D, and was sold worldwide.  So for those of us in places like North America and Australia, we never saw the plastic one because the metal version is the only one that was sold.

Not quite correct Andrew. Here in Australia all three models (flat, plastic & metal) were available.

cheers,

Lance

[RobertB]

But it's still more uncommon than the plastic version, isn't it?

     Relatively common here in North America.

There is also supposed to exist a flat C128CR, has anyone seen one or has got one?

     No, I don't know of the existence of that one.  Of course, Bil Herd would know best. 

                Truly,
                Robert Bernardo
                Fresno Commodore User Group
                http://videocam.net.au/fcug
                The Other Group of Amigoids
                http://www.calweb.com/~rabel1/
                Southern California Commodore/Amiga Network
                http://www.sccaners.org/