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CMB PET 3032 ( 2001N BOARD )

So, I am expecting to see this trace ALWAYS like this on the screen. You appear to have set the oscilloscope up correctly.

If you look back at post #1,096 we get nothing like that do we?

Can you double check that the ALT/CHOP button is pressed IN.

You may need to adjust the oscilloscope trigger level to get the desired result.

What does your piece of paper look like, because you can't have git the four /CAS0 pulses between the pairs of UD8 pin 20 pulses...

Dave
 
daver2 said:
So, I am expecting to see this trace ALWAYS like this on the screen. You appear to have set the oscilloscope up correctly.

If you look back at post #1,096 we get nothing like that do we?

Can you double check that the ALT/CHOP button is pressed IN.

You may need to adjust the oscilloscope trigger level to get the desired result.

What does your piece of paper look like, because you can't have git the four /CAS0 pulses between the pairs of UD8 pin 20 pulses...

Dave
Click to expand...
This is pièce of paper
 

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That's better.

You can still move the traces closer together by tweaking the Y POSITION controls. It will make it easier to compare the traces.

You may need to readjust the timebase trigger level again.

Dave
 
daver2 said:
That's better.

You can still move the traces closer together by tweaking the Y POSITION controls. It will make it easier to compare the traces.

You may need to readjust the timebase trigger level again.

Dave
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in this case i pressed again Chop button....unfortunately it is not possible to understand when the key is pressed or not...
 
Desperado said:
in this case i pressed again Chop button....unfortunately it is not possible to understand when the key is pressed or not...
Click to expand...

Ah, so you were in ALT mode not CHOP mode. In one case (CHOP) the button will be further IN than in the other case. You press the button and see whether it goes in further or comes out. I would always suggest this control be left in the CHOP mode.

Before we carry on, because we have now identified a knowledge gap in your understanding, read up on the difference between ALT and CHOP mode to identify why I am suggesting one mode over another when we are trying to compare the timing of the two oscilloscope channels. This is VERY important, and may indicate why we are having so many problems with your oscilloscope readings (not just now but in the past).

Dave
 
daver2 said:
Ah, so you were in ALT mode not CHOP mode. In one case (CHOP) the button will be further IN than in the other case. You press the button and see whether it goes in further or comes out. I would always suggest this control be left in the CHOP mode.
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I am desperate because i can t see any difference to button s' distance...
 
Ok this is button at the actual status (first picture) and in the other position (second)
 

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In the first photograph the plastic lever is further out than in the second photograph.

Not by much - but enough...

Can you see that or not?

Dave
 
daver2 said:
In the first photograph the plastic lever is further out than in the second photograph.

Not by much - but enough...

Can you see that or not?

Dave
Click to expand...
yes now i see....so the last pictures of the scope screen are made with ALT mode :(
 
The REPAIR is not getting mote difficult. It is your knowledge of how to use the tools (i.e. your oscilloscope) that is letting you down again.

Also, in addition, your oscilloscope trace (as shown in post #1,107) does still not match your marks on your paper (as shown in post #1,102).

Assuming you are (were) monitoring the same signal (/CAS0 on I2 pin 15), then we still have an unexplained discrepency somewhere.

In order to achieve the necessary information I require from your PET, you have to be able to deliver reliable (and consistent) results from your oscilloscope readings.

If not, there is no point in using your oscilloscope, we can't get the results I require and, therefore, we can't fix these more complex faults as a result.

I suggest you take some time out to improve your knowledge and use of the oscilloscope as a measurement tool before we continue.

What do you want to do? Or do you just want to replace the DRAM address multiplexers on a whim, and then we continue with the above when (if) that doesn't work? Or, you never know, you may accidentally get lucky...

Dave
 
daver2 said:
What do you want to do? Or do you just want to replace the DRAM address multiplexers on a whim, and then we continue with the above when (if) that doesn't work? Or, you never know, you may accidentally get lucky...
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At this point I will try to replace the multiplexers one at a time... (provided this has at least one chance to resolve the error).... or do you recommend continuing with the tests?
 
We are not continuing with the tests until you become more proficient with your oscilloscope. We are both wasting our time (in my opinion).

I (personally) would not replace the multiplexers until I knew they were faulty. This is, after all, what the oscilloscope, your brain and the test software should indicate. But, if you can't configure your oscilloscope correctly (or understand that you have misconfigured it) then it is no more use than a doorstop I am afraid.

I do belive (in one of the many, many posts) that I have recommended the order in which you replace the multiplexers - as (based upon the PETTESTER results) some multiplexers are more likely at fault than the others.

In any case, I would get the PETTESTER running (with the g, b and . display) and replace the multiplexers one at a time and look for changes in the PETTESTER display after each IC replacement.

Dave
 
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