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Cbm pet 8296-d black screen

Dave_C78

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Wait until you get the "countdown" message. You should observe a line of 00's for the keyboard display with no keys pressed and you should see a single 1, 2, 4 or 8 display
I inserted UB16 mos 6520 in UB12 but i have always same char lines :( Possible two bad 6520???!! Or bad socket???
 

daver2

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>>> Possible two bad 6520???!! Or bad socket?

It could be either.

I would remove UB12 and UB16 then (to save confusing ourselves).

Next would be to put the EDIT ROM back in place of the PETTESTER ROM.

Do you still get the random screen on startup?

Check the CPU SYNC pin (UB14 pin 7) for signs of activity (pulsing) using your logic probe.

Also check CPU (UB14) pins 6 (/NMI) and 4 (/IRQ) using your logic probe and report back your findings (PULSING, HIGH or LOW).

Dave
 

Dave_C78

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I re-burned 901474-04 edit rom, verify ok but when i insert i have black screen now... im desperate!!!!
 

Dave_C78

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UB14 PIN7: LOW
UB14 PIN 6: HIGH
UB14 PIN 4: HIGH

When i turn on, i hear start up sound!
 

daver2

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So that's good hearing the 'chirp' :)!

Pin 7 being LOW indicates that the CPU has stopped executing instructions.

Do you have UB12 or UB16 in place?

Dave
 

Dave_C78

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So that's good hearing the 'chirp' :)!

Pin 7 being LOW indicates that the CPU has stopped executing instructions.

Do you have UB12 or UB16 in place?

Dave
No at moment not ub12 and not ub16
 

daver2

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It's odd that you haven't got any pulsing signal on UB14 pin 7.

But, if both 6520's are dead (or dying), I can understand why.

I would suggest that this is as far as we go until you get a replacement 6520.

However, you could check the continuity of all of the pins of UB16 and UB12 with the PCB itself. Use one of the 6520's in the socket you are testing at a time.

It might also be worth testing the continuity of the VIA (UB15) with the socket as well.

Dave
 

Dave_C78

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Dave! I tryied to turn on and i saw basic screen!! If i turn off an i turn on i have black screen....
Why i can't see always basic screen???
 

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daver2

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In the meantime I managed to the the code for my TINY BASIC interpreter for the CRAY-1 supercomputer working! I was stuck on the FOR/NEXT loop (in particularly the NEXT statement). But I have managed to resolve it between looking at your posts.

The original TINY BASIC worked with 16-bit signed integers, so was in the range -32768 to +32767. The CRAY-1 has 64-bit registers, so my TINY BASIC numbers are not so tiny anymore!

I have a few error checks missing from Li-Chen Wang's original code - but I will get around to adding them in at some point.

My next task is to implement the LOAD command and get Star Trek running :)!!!

Dave
 

Dave_C78

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In the meantime I managed to the the code for my TINY BASIC interpreter for the CRAY-1 supercomputer working! I was stuck on the FOR/NEXT loop (in particularly the NEXT statement). But I have managed to resolve it between looking at your posts.

The original TINY BASIC worked with 16-bit signed integers, so was in the range -32768 to +32767. The CRAY-1 has 64-bit registers, so my TINY BASIC numbers are not so tiny anymore!

I have a few error checks missing from Li-Chen Wang's original code - but I will get around to adding them in at some point.

My next task is to implement the LOAD command and get Star Trek running :)!!!

Dave
Wow!!! Wine for all tonight ;)))
 

daver2

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The question is - is it a black screen or a blank screen?

Check UC2 pin 6 (VERT DRIVE), UC2 pin 3 (HORIZ DRIVE) and UC2 pin 8 (/VIDEO) for signs of activity along with UB14 pin 7 (SYNC).

You should observe pulses on UB14 pin 7 if the CPU is executing instructions.

You should observe pulses on UC2 pins 3 and 6 if the CPU has initialised the CRT Controller chip correctly.

There may still be some issues regarding stability - causing some random effects to occur.

You may still have some issues with IC socket connections.

You may still have the odd problem with other ICs that my PETTESTER doesn't test (for example, the VIA).

My suggestion would be to leave the PET running my PETTESTER memory test for as long as you can tomorrow to flush out any potential glitches.

You are not far off now - at least you know there is nothing 'terminal'.

Wine tomorrow...

Dave
 

Dave_C78

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The question is - is it a black screen or a blank screen?

Check UC2 pin 6 (VERT DRIVE), UC2 pin 3 (HORIZ DRIVE) and UC2 pin 8 (/VIDEO) for signs of activity along with UB14 pin 7 (SYNC).

You should observe pulses on UB14 pin 7 if the CPU is executing instructions.

You should observe pulses on UC2 pins 3 and 6 if the CPU has initialised the CRT Controller chip correctly.

There may still be some issues regarding stability - causing some random effects to occur.

You may still have some issues with IC socket connections.

You may still have the odd problem with other ICs that my PETTESTER doesn't test (for example, the VIA).

My suggestion would be to leave the PET running my PETTESTER memory test for as long as you can tomorrow to flush out any potential glitches.

You are not far off now - at least you know there is nothing 'terminal'.

Wine tomorrow...

Dave
When i see Basic screen, i have pulse on UC2 pin 3,6 and 8 and Cpu pin 7!
When i have blank or black screen i have high signal on UC2 pin 8 and low on Cpu pin 7!
 

daver2

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>>> When i have blank or black screen i have high signal on UC2 pin 8 and low on Cpu pin 7!

The important thing you are not telling me here is the state of UC2 pins 3 and 6 as well. Are they pulsing (indicating that the CRTC has been initialised)?

Dave
 

tradde

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In the meantime I managed to the the code for my TINY BASIC interpreter for the CRAY-1 supercomputer working! I was stuck on the FOR/NEXT loop (in particularly the NEXT statement). But I have managed to resolve it between looking at your posts.

The original TINY BASIC worked with 16-bit signed integers, so was in the range -32768 to +32767. The CRAY-1 has 64-bit registers, so my TINY BASIC numbers are not so tiny anymore!

I have a few error checks missing from Li-Chen Wang's original code - but I will get around to adding them in at some point.

My next task is to implement the LOAD command and get Star Trek running :)!!!

Dave
You're going to play Star Trek on a Cray? How awesome is that.
 

daver2

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Well, it will have to be on a Cray simulator for the time being!

A convenient (operational) Cray being currently unavailable. Not to mention the cost of the electricity to run it!

Dave
 

tradde

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Bah, electricity. :) Even running it on a simulated Cray sounds like fun. Which version of ST? The one from 101 games? The bigger one with Romulans? There are so many floating around out there.
 
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