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C64 IN PET S' CASE

Isn't the yellow wire the video signal?

This is the pinout of the J7 connector of a Commodore PET 2001 (320081):

1 YELLOW - VIDEO.
2 WHITE - 0V/GND.
3 ORANGE - VDRIVE.
4 WHITE - 0V/GND.
5 GREEN - HDRIVE.
6 Key
7 WHITE - 0V/GND.

Which is the same as your image in post #2,609.

Are you sure your yellow wire is pin 7?

Dave
 
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daver2 said:
Isn't the yellow wire the video signal?

This is the pinout of the J7 connector of a Commodore PET 2001 (320081):

1 YELLOW - VIDEO.
2 WHITE - 0V/GND.
3 ORANGE - VDRIVE.
4 WHITE - 0V/GND.
5 GREEN - HDRIVE.
6 Key
7 WHITE - 0V/GND.

Which is the same as your image in post #2,609.

Are you sure your yellow wire is pin 7?

Dave
Click to expand...
on the transparent plastic connector there are numbers from 1 to 7. The number 7 corresponds to the yellow wire.
 
It doesn't matter what the number is on the connector providing the wires are connected to the right signals.

I have machines at work (in excess of 80 of them) containing communications cards all with connectors that are numbered differently to the schematics. If you use the numbers on the connector - it doesn't work...

Dave
 
daver2 said:
It doesn't matter what the number is on the connector providing the wires are connected to the right signals.

I have machines at work (in excess of 80 of them) containing communications cards all with connectors that are numbered differently to the schematics. If you use the numbers on the connector - it doesn't work...

Dave
Click to expand...
Ok, anyway I had connected correctly. However, I am using only one pin for the gnd, pin 4. That's fine right?
 
The reason multiple ground pins are put on cables is to reduce electrically induced noise between the cables.

Ideally, the 0V return cable should be twisted with the associated signal cable - but I don't think Commodore carried it that far...

There is sometimes more to 0V/GND cables than a 0V signal reference... Although the multiple cables also help.

Dave
 
daver2 said:
The reason multiple ground pins are put on cables is to reduce electrically induced noise between the cables.

Ideally, the 0V return cable should be twisted with the associated signal cable - but I don't think Commodore carried it that far...

There is sometimes more to 0V/GND cables than a 0V signal reference... Although the multiple cables also help.

Dave
Click to expand...
So what can i do now?
There is something strange on screen :(
 
>>> so try adjusting R12 to a lower value and see if it improves the stability on the VDU

Hugo asked you to adjust R12 to a lower value.

Did you actually do this?

Dave
 
daver2 said:
>>> so try adjusting R12 to a lower value and see if it improves the stability on the VDU

Hugo asked you to adjust R12 to a lower value.

Did you actually do this?

Dave
Click to expand...
Yes i turned this R12 but i have bad screen
 
Let Hugo look at the signals and see if he sees anything that needs adjusting.

It may be that we have to adjust the other potentiometers a bit more.

Dave
 
The V & H drive look ok on the scope and the /Hblnk signal does too, so we will have to assume for now there is a problem in the video signal.

As an experiment, bend pin 8 of IC 1 out of its socket (this disconnects the video) and ground the video line leading to the VDU. This should make the whole screen light up, you can turn the VDU brightness down low, But what should be seen is a perfectly stable raster scan on the VDU, with a few tilted vertical scan retrace lines, if all is actually well with those H & V drive pulses.

Then you can un-ground the video line, it will then go to +5V and the raster scan should black out, though you still may be able to see it if you turn the brightness control on the VDU to full.
 
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I'm at work now, I'll proceed with the test this evening.
I suspect the problem is the video signal having too low voltage. When I adjusted R12 I had reached the full scale and we had not exceeded the 2 V required by Hugo.
 
Desperado said:
I'm at work now, I'll proceed with the test this evening.
I suspect the problem is the video signal having too low voltage. When I adjusted R12 I had reached the full scale and we had not exceeded the 2 V required by Hugo.
Click to expand...
you could try changing R12 to a 2k preset (I think you have one)
 
Hugo Holden said:
As an experiment, bend pin 8 of IC 1 out of its socket (this disconnects the video) and ground the video line leading to the VDU. This should make the whole screen light up, you can turn the VDU brightness down low,
Click to expand...
i can't see anything at screen :(
 
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