C64 IN PET S' CASE

[Desperado]

Black...
And also with R12 2K it's the same screen....

 

[daver2]

Do you still have HDRIVE and VDRIVE signals to the monitor?

Dave

 

[Desperado]

I suspect that i have a bad Vic IC on C64....the right video signal is not arriving from pin 15 of the Vic

 

[Desperado]

Do you still have HDRIVE and VDRIVE signals to the monitor?

Dave

yes i have good H and V signals

 

[Desperado]

Time to raise up the damn white flag now....Italy lose at this time

 

[antony]

I prefer the tricolor one, w Italy

 

[antony]

from the video it seems that the vertical signal is insufficient, there is something we are forgetting but I don't know what

 

[daver2]

I suspect that i have a bad Vic IC on C64....the right video signal is not arriving from pin 15 of the Vic

I actually disagree with your assessment.

The video that you posted previously quite clearly showed a reasonable video signal on the PET monitor.

If you are going to give up, it would make sense to perform some 'controlled potentiometer adjustment' if we go back to when we had an unstable video signal on the PET monitor, and monitoring the VDRIVE (and HDRIVE) signal with the oscilloscope when you adjust the potentiometers.

Dave

 

[Desperado]

I actually disagree with your assessment.

Why you disagree my assessment Sir?

 

[daver2]

Why you disagree my assessment Sir?

I posted the reason in my last post... I always try to give you a reason...

What have you actually done since post #2,612?

Have you replaced R12 and (if so) how have you adjusted the screw?

You have bent a pin out of IC1. Have you accidentally connected the pin of the IC that you have bent out to 0V or the video signal to the PET monitor?

Have you measured the HRIVE and VDRIVE signals with the PET monitor connected or not?

I am trying to work out why you have bot git a white screen on the PET monitor (even if it is not synchronised properly).

Dave

 

[Desperado]

Have you replaced R12 and (if so) how have you adjusted the screw?

in both ways but without success....

Have you accidentally connected the pin of the IC that you have bent out to 0V or the video signal to the PET monitor?

not....

Have you measured the HRIVE and VDRIVE signals with the PET monitor connected or not?

not yet....

 

[daver2]

>>> not yet....

That is what I asked you in post #2,642 and you responded with:

>>> yes i have good H and V signals

How do you know if you haven't measured them?

Dave

 

[Hugo Holden]

The thing is though, in this board's current configuration, is really just matched the old one that Desperado threw away. That one was working, the only quirk that remained was a buzz when the H center preset was set. So I'm not sure why this board has been so difficult to get running. Though there was a 470 Ohm pullup resistor (probably) on the first board that I think got discarded with the board.

In the past I made a different kind of circuit to process composite video and drive a 9" PET VDU, I would have to dig around. If worse comes to worse and Desperado cannot make this current one work, I could build and test one that would definitely work at least on a composite video source in the workshop.

 

[Desperado]

>>> not yet....

That is what I asked you in post #2,642 and you responded with:

>>> yes i have good H and V signals

How do you know if you haven't measured them?

Dave

I measured but without CRT connected..

 

[daver2]

So, what happens if you connect the monitor and it shorts out one or both signals?

The signal is there with the monitor disconnected but not there with the monitor connected!

The same for the video signal.

What do the signals (HDRIVE, VDRIVE and VIDEO) look like with the PET monitor connected preferably on the PET monitor itself to make sure we have the cable connected correctly?

Dave

 

[Desperado]

So, what happens if you connect the monitor and it shorts out one or both signals?

The signal is there with the monitor disconnected but not there with the monitor connected!

The same for the video signal.

What do the signals (HDRIVE, VDRIVE and VIDEO) look like with the PET monitor connected preferably on the PET monitor itself to make sure we have the cable connected correctly?

Dave

Maybe the CRT is broken?

 

[daver2]

Here you go, guessing again - but it is always a possibility.

GET SOME DATA POINTS (EVIDENCE, FACTS) RATHER THAN GUESSING!

Dave

 

[Desperado]

Tomorrow Dave.... It s late now here.... Time to desperate night
Time to come back with the old pcb?

 

[Desperado]

However, I noticed that by adjusting R12 both on one side and the other, almost nothing changes on the screen

 

[daver2]

If you have a picture of a black cat in a coal cellar at midnight on the monitor screen, this may be due to any number of reasons. Adjusting R12 and looking at the screen does not help anyone one iota.

What have I already told you many, many times before?

Use the oscilloscope...

The purpose of R12 is to adjust the composite video signal from the C64 in order to 'match' the input to the transistorised separator consisting of Q1 and Q2. The purpose of this circuit is to extract the VIDEO signal and the COMPOSITE SYNCHRONISATION signal from the C64 composite signal.

The extracted VIDEO signal should have no synchronisation pulses polluting it.

Likewise, the extracted COMPOSITE SYNCHRONISATION signal should have no video signal polluting it.

You can, therefore, only adjust R12 by connecting an an oscilloscope to the two identified points and monitoring them 'by eye'.

However, in order to do this, you have to know what you are looking for. I have already explained this to you.

After that, you 'chase' the signals through the logic gates until you get the to the HDRIVE, VDRIVE and VIDEO signals of the monitor.

If any of the signals are missing, you need to ask yourself why.

If all of the signals are present, then we can work with that moving forwards.

Dave