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C64 IN PET S' CASE

Sorry for being a bit late.

Leave channel 2 on IC2/2 as a trigger and move channel 1 to look at IC2 pins 5 and 12.

Pins 5 and 12 should be in antiphase with each other again.

Adjusting R14 should MOVE the trigger point of channel 1 relative to channel 2. Adjusting R15 should increase (and decrease) the channel 1 pulse width.

Dave
 
This is the second inconsistent measurement we have got now.

Either there is something wrong with your circuit wiring, something wrong with the test configuration, something wrong with my instructions to you to perform the tests, something wrong with the way you are performing my instructions to you incorrectly or something wrong with realty. I am sure I may have missed a few other things out in the process...

Let me think some more...

Dave
 
R14 should affect the pulse width on IC2A pins 4/13.
R15 should affect the pulse width on IC2B pins 5/12.
R11 should affect the pulse width on IC3B pins 5/12.
R12 should affect the pulse width on IC3A pins 4/13.

The trigger from IC2A drives IC2B and IC3B.

Channel 2 should be driven from IC2/2 (which is an INPUT into the monostable tree). As such, the variable resistors CANNOT adjust the pulse width on channel 2 under any circumstances.

We should be moving channel 1 around to measure the various monostable outputs - so the only thing that should be varying/moving with our potentiometer adjustment is channel 1.

You must, therefore, have the oscilloscope probe connections configured incorrectly.

Dave
 
R14 should affect the pulse width on IC2 pins 4/13.
R15 should affect the pulse width on IC2 pins 5/12.
R11 should affect the pulse width on IC3 pins 5/12.
R12 should affect the pulse width on IC3 pins 4/13.

The trigger from IC2? drives IC2? and IC3?.

Dave
I am desperate now!!!
 
I have just updated the post above - give me chance to complete my posts before getting desperate!

You may get desperate now... Only joking! Check which pins the oscilloscope probes are connected to please and report back.

Dave
 
IC2/2 is the synchronising pulse from the C64 modified by the level shifters on your interface board.

It is an INPUT to this circuit and NONE of the monostables on your board (controlled by the potentiometers) can EVER affect it.

Therefore is it possible you are confusing yourself by what you are seeing on the oscilloscope screen?

Is it possible to post a video of what you are observing?

Dave
 
IC2/2 is the synchronising pulse from the C64 modified by the level shifters on your interface board.

It is an INPUT to this circuit and NONE of the monostables on your board (controlled by the potentiometers) can EVER affect it.

Therefore is it possible you are confusing yourself by what you are seeing on the oscilloscope screen?

Is it possible to post a video of what you are observing?

Dave
Video with ch2 on ic2 pin2?
 
I am desperate now! I soldered a wire on ic2 under board now, and i connected ch1 probe.. Now i have this 😭
 

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It is not supposed to be...

Read post #1,422. IC2 pins 5 and 12 should be in antiphase with each other - not the pins that are being measured by channels 1 and 2 of the oscilloscope!

Let me reiterate again:

Channel 2 of the oscilloscope is ALWAYS going to be measuring IC2 pin 2 as the trigger and you are going to use channel 1 of the oscilloscope to measure the various other pins.

As a result, you put Channel 1 on IC2 pin 5, make a note of what the signal looks like (e.g. take a photograph) and THEN move Channel 1 to IC2 pin 12. This pin should be the antiphase of the photograph you took...

What I am interested in is then what happens when you twiddle the two potentiometers I specified.

Channel 2 (the trigger) should ALWAYS stay the same (invariant) as it should NOT be affected by the potentiometers.

Dave
 
hi guys, @daver2 @Hugo Holden I have completed the new drawing and I would like you to check if everything is ok.
I drew without tags because I noticed you don't like them.
please report any errors because I'm learning, thanks.
If it helps but I discovered an error with the monitor connector on the previous PCB.
 

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Let's sort out the "antiphase" issue in one go shall we?

Oscilloscope channel 2 on IC2 pin 2 as the trigger. Leave it there...

Then use oscilloscope channel 1 to measure each of the following pins, taking a photograph and posting the result after each measurement:

IC2 pins 4, 13, 5 and 12.

IC3 pins 4.13, 5 and 12.

Dave
 
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