Video problem

[Rinconete]

However, the R-Y signal is not directly connected to the VDU. It goes through two ICs (4053, 2318) before it finally gets to the R-Y input of the LM1889. I have checked the power pins (+5V) and seem to be right. You are right, I should also check all the connections of the OA signal from the VDU to the modulator.

I have found a broken track and the OA 2348 (IC28) had one of its inputs in high impedance instead of the chroma bias signal. I have fixed it and... it works!!!!!!

Now I can see the picture on the TV: green paper, black ink, and black border. Is this correct?

[Alastair]

Now I can see the picture on the TV: green paper, black ink, and black border. Is this correct?

That's correct. Now try typing in
EXEC [return]
to change into Dragon 64 mode, the cursor should turn flashing blue.

Next try the following program
10 SCREEN 0,1
20 GOTO 20
and RUN it, the screen should change to black text on an orange background.

After BREAKing the above you may wish to test the various CLS colours with
CLS x

where x is:
0 - Black
1 - Green
2 - Yellow
3 - Blue
4 - Red
5 - White
6 - Light Blue
7 - Purple
8 - Orange
9 (to 255) - Green with Microsoft copyright (whatever happened to them?)

[Rinconete]

Thanks, it works I can see all the colors!!

Anyway, I will complete the schematic for the video section and I will post it here as soon as it is finished.

Thanks for your help!

Now I should build a cassette lead and try loading a program. I accept recommendations

[sixxie]

I'll check my A3 photocopies of the Dragon 64 one when I get home on Monday

At least I would, if I knew where they were. Sorry, it's not in either of my Dragon docs boxes, so it might take a while to find.

Edit: oh, but well done on getting the last bit fixed

[Alastair]

Now I should build a cassette lead and try loading a program. I accept recommendations

That's a tricky one to answer, do you have any joysticks? For a Gauntlet style game you may want to try "Glove" ( http://archive.worldofdragon.org/index.php?title=GLOVE ). If you have a working joystick and wish to try out arcade style games released back in the eighties you could try "Cuthbert in the Jungle" (Microdeal) and "Donkey King" (Microdeal), or if you do not have a joystick, "Manic Miner" (Software Projects) and its sequel "Jet Set Willy" (Software Projects).

For RPGs try "The Ring of Darkness" (Wintersoft) and its sequel "Return of the Ring" (Wintersoft). For text adventures anything by Adventure International or Channel 8 Software, also "Black Sanctum" (Dragon Data Ltd.) and "Calixto Island" (Dragon Data Ltd.) come to mind. "Juxtaposition" (Wintersoft) is a text adventure and combined with a 3D environment (when outside). Finally for a football management game try "Champions!" (Peaksoft).

[Rinconete]

I'll check my A3 photocopies of the Dragon 64 one when I get home on Monday

At least I would, if I knew where they were. Sorry, it's not in either of my Dragon docs boxes, so it might take a while to find.

Edit: oh, but well done on getting the last bit fixed

oh, ok, thanks anyway!

[Rinconete]

Now I should build a cassette lead and try loading a program. I accept recommendations

That's a tricky one to answer, do you have any joysticks? For a Gauntlet style game you may want to try "Glove" ( http://archive.worldofdragon.org/index.php?title=GLOVE ). If you have a working joystick and wish to try out arcade style games released back in the eighties you could try "Cuthbert in the Jungle" (Microdeal) and "Donkey King" (Microdeal), or if you do not have a joystick, "Manic Miner" (Software Projects) and its sequel "Jet Set Willy" (Software Projects).

For RPGs try "The Ring of Darkness" (Wintersoft) and its sequel "Return of the Ring" (Wintersoft). For text adventures anything by Adventure International or Channel 8 Software, also "Black Sanctum" (Dragon Data Ltd.) and "Calixto Island" (Dragon Data Ltd.) come to mind. "Juxtaposition" (Wintersoft) is a text adventure and combined with a 3D environment (when outside). Finally for a football management game try "Champions!" (Peaksoft).

sorry for the late reply, I have been having problems with the Internet, the link has been going up and down

Thanks for your recommendations. mmm, I think I have a pair of joysticks but I still do not know if they work. Yes I am going to try out them with some of the games you recommend. I will come back with the results!

[Rinconete]

I have just finished the schematic of the video section. You may find the files in the upload section. There is a pdf (A3) with the whole circuit in it. Could anyone please check the text grammar?. Thanks!

[Rinconete]

New Dragon 64K PAL Video Schematic v3 (see upload subforum)

The schematic has been captured using the open source tool KiCAD. The shape of most of the parts has been redesigned to match the look of the Dragon Data schematic and included in a lib file. Although I have checked each part, line, ref and value against the original schematic and the PCB, using a multimeter, the schematic is provided 'as is'. Since I am unable to read the capacitor values they are not specified.

Some minor differences between the Dragon Data schematic and the PCB have been found. All of them are documented by means of text notes at the specific places.

I would like to thank mcleod_ideafix, sixxie and Alastair for his unvaluable support on fixing my Dragon 64 by providing some definitive documentation and suggesting some clever hints that led me to the fault.