Topic: C128D vertical scrolling on 1080 monitor, C128 works OK?

[Kremlar]

Hey guys -

Just getting into the retro computer world.  I had and loved my C64 back in the day, then went straight to the Amiga - never owned a C128.  Picked up a bunch of stuff and now trying to put it all together. 

I have a Commodore/Amiga 1080 montitor with a 9-pin RGB connector, and a cable that works 100% with my C128.  80 column mode works fine.

Question #1:  Am I correct that 80 column mode is the only mode that works over the RGB output?  If I switch the C128 to 40 column mode or go to C64 mode only the composite output works.

Anyway, that's it for the back story.  Now on to my 128D where my problems arise:

Before I got the RGB monitor and cable I was messing with the 128D and tried putting it in 80 column mode with only a composite output.  Once I did that I could not get it to boot into 128 mode even using 40 columns - just hang on boot.  I found I could boot direct into C64 mode by holding the C= key.  I thought something fried, but I found that after "resting" the computer for a while 128 mode started working again.  I repeated this one more time with the same results which seems very strange, but nonetheless true.

So, fast forward to today.  I have the 1080 and an RGB cable that both work on my C128 so thought I'd try them on my 128D.  It does boot into 80 column mode, but the picture scrolls vertically and I cannot get the scrolling to stop no matter how I adjust the 1080 VHOLD knob.

I did a bit of googling (dangerous) and thought the problem might be with the 8563 chip, so I thought I'd open my C128 and C128D and swap the chip between the two to see what happened but found that my C128D had an 8568 chip in its place.

So, back to square one.  Any suggestions on what could be causing this issue on my C128D?  How should I go about trying to solve?

Thanks!!!!

[wte]

Wellcome in the world of C128 users!

Question #1:  Am I correct that 80 column mode is the only mode that works over the RGB output?  If I switch the C128 to 40 column mode or go to C64 mode only the composite output works.

Yes, that's correct!

So, fast forward to today.  I have the 1080 and an RGB cable that both work on my C128 so thought I'd try them on my 128D.  It does boot into 80 column mode, but the picture scrolls vertically and I cannot get the scrolling to stop no matter how I adjust the 1080 VHOLD knob.

That's strange. Could it be a NTSC/PAL problem?

I did a bit of googling (dangerous) and thought the problem might be with the 8563 chip, so I thought I'd open my C128 and C128D and swap the chip between the two to see what happened but found that my C128D had an 8568 chip in its place.

So, back to square one.  Any suggestions on what could be causing this issue on my C128D?  How should I go about trying to solve?

Sorry, I've no clue. The 8568 is the successor of the 8563. Owing to differences in pin assignments and circuit interfacing, the 8563 and 8568 are not electrically interchangeable (Wikipedia).

Regards WTE
 

[Kremlar]

Wellcome in the world of C128 users!

Thanks! 

That's strange. Could it be a NTSC/PAL problem?

Don't think so, everything should be NTSC....

[RobertB]

Before I got the RGB monitor and cable I was messing with the 128D and tried putting it in 80 column mode with only a composite output.  Once I did that I could not get it to boot into 128 mode even using 40 columns - just hang on boot.  I found I could boot direct into C64 mode by holding the C= key.  I thought something fried, but I found that after "resting" the computer for a while 128 mode started working again.  I repeated this one more time with the same results which seems very strange, but nonetheless true.

     That sounds like a computer problem, but I wouldn't blame the 8568 chip.

I have the 1080 and an RGB cable that both work on my C128 so thought I'd try them on my 128D.  It does boot into 80 column mode, but the picture scrolls vertically and I cannot get the scrolling to stop no matter how I adjust the 1080 VHOLD knob.

     That is a monitor problem.  I have a Magnavox RGB/composite monitor that does the same thing, except it only happens after the monitor has been used awhile.  When cold, the monitor is fine.  I should have Ray Carlsen look into it, but I'm bringing Ray a multiscan monitor (for the Amiga) for him to diagnose.

          Writing from the Portland, Oregon area,
          Robert Bernardo
          Fresno Commodore User Group
          http://videocam.net.au/fcug

[Kremlar]

Thanks for the reply!  Well, things have gotten a bit more interesting.

I initially thought the scrolling was a monitor issue as well, but the fact that it worked 100% fine on my normal C128 made me suspect the C128D as having an issue.

BUT last night I picked up a Sears SR3000 RGB monitor with cable for $10 off Craigslist and thought I'd give it a shot.  Sure enough, works fine on the C128D.  So, there must be some difference between the C128 and C128D regarding the RGB output?  Why would 1 work and not the other on the same monitor & cable?

Anyway, I want to try another cable with the C128D and 1080 monitor.  I assumed the cable I had was good but there is a pin missing, not sure if that's normal.  From what I understand I can use a straight through 9-pin M-F cable between the C128D and 1080 monitor.

As for the Sears SR3000, quality looks OK over the RGB connection as far as I can tell - nice, crisp green text.  BUT the composite input seems mucked up.  Coloring is odd, like part of the signal is missing.    Need to test more.

[RobertB]

Anyway, I want to try another cable with the C128D and 1080 monitor.  I assumed the cable I had was good but there is a pin missing, not sure if that's normal.

     Hmm, it depends which pin is missing.  Go to

          http://www.retroisle.com/commodore/c64128/Technical/Hardware/c128ports.php

and scroll down to see a description of the C128's RGB port.

               Writing from Portland, Oregon still,
               Robert Bernardo
               Fresno Commodore User Group
               http://videocam.net.au/fcug

[Hydrophilic]

As I recall, the cable for my 1902A monitor was also missing one pin -- the one for monochrome (pin 7).  You can see a photo / diagram in this post... of course that is showing the connector on the back of the C128 so the direction would be reversed looking at your cable.
 
I don't own C128D to be sure, but on the C128 there is a 74LS244 buffer chip (U24) between the VDC chip and the video connector.  It sounds like it is producing a marginal output -- good enough for your Sears monitor but not your 1084... either that or your 1084 is starting to fail.  I would suspect the monitor as it does not seem very common for TTL buffers to fail under normal conditions...

[Kremlar]

OK, I ended up replacing it with a 9-pin M-F straight through cable I had kicking around and I was able to get it to sync.

As for the other cable, pin 8 was the one missing which is labeled Horizontal Sync in the diagrams I can find.  Not sure why it worked on the 128 but not the 128D, but I'm just going to trash it at this point.

The 128D was behaving fine during my quick testing, but today I went to play more and once again it will not boot into 128 mode - only 64 mode.  I'm sure if I let it rest a while it will start booting.

Kind of sad... of course I'll probably use it 99% of the time in 64 mode, but really wanted a fully working 128D.

Anyone have any suggestions on what I could try replacing?

Thanks guys...

[RobertB]

The 128D was behaving fine during my quick testing, but today I went to play more and once again it will not boot into 128 mode - only 64 mode.  I'm sure if I let it rest a while it will start booting.

     On the repaired, flat 128 that I just picked up from Ray Carlsen, he diagnosed its not going into 128 mode as being a bad power switch.  He said that a bad power switch can manifest itself in all kinds of symptoms... no 128 mode, no sound, bad video.

          Don't know if that would help in your 128D,
          Robert Bernardo
          Fresno Commodore User Group
          http://videocam.net.au/fcug

[Kremlar]

Hmm, that seems odd....  thanks for the tip.

I pulled all socketed chips, cleaned the pins up as well as I could, and re-seated them.  While I had it open I cleaned the disk drive heads, also cleaned and applied some new thermal paste to the chips under that metal shield/heat sink.

I also went ahead and installed a fan per this thread:
http://www.commodore128.org/index.php?topic=3580.0

I soldered a power connector to the unused leads per that article, then plugged in and mounted an Antec 60mm 12V fan I had around.  It's a bit noisy for my taste, so I'm going to try out a fan speed reducer (drops it to 7V I believe).  I might have one kicking around my office I can try.

I also saw this guy went crazy with heat sinks on his 128D:
http://www.commodore128.org/index.php?topic=2984.0

Very tempting, not sure if it's worth it or not, or what a good source for the heat sinks might be.

Anyway, I've been playing with it for a bit and have not had any issues... yet.  Here's hoping the chip re-seating helped.

Unfortunately I don't have much software to try at the moment.  I'm thinking of going with an SD card interface of some sort... maybe a UIEC or 1541 Ultimate II - but I'm not 100% sure of the differences - but that's a subject for another thread!

[Kremlar]

Just found a blown/leaking resistor, not sure if it's related so started a new thread:
http://www.commodore128.org/index.php?topic=4197.msg20684#msg20684

Anyone know how I can find the value of this so I can source a good replacement?

Thanks

[RobertB]

I'm thinking of going with an SD card interface of some sort... maybe a UIEC or 1541 Ultimate II - but I'm not 100% sure of the differences...

     Here is a quick but not comprehensive comparison of the sister SD card drives -- uIEC/SD from Jim Brain, SD2IEC from NKCElectronics.com, C64SD v2.0 Infinity from Manosoft -- and the 1541 Ultimate from Gideon Zweijtzer:

uIEC/SD / SD2IEC / C64SD v2.0 Infinity -- cheaper
1541 Ultimate -- more expensive

uIEC/SD / SD2IEC / C64SD v2.0 Infinity -- immediately available
1541 Ultimate -- waiting list

uIEC/SD / SD2IEC / C64SD v2.0 Infinity -- less compatible
1541 Ultimate -- more compatible

     The list does not include the 1541-III (which does not use the sd2iec firmware) nor the IDE64 v4.1 (CompactFlash but can use a CF-to-SD adapter) nor the uIEC/CF.

          Truly,
          Robert Bernardo
          Fresno Commodore User Group
          http://videocam.netau/fcug

[Kremlar]

Thanks for the info!  Will have to make some time to dig into it and see what exactly is the best for me.