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hyuma

Trying to fix Colecovision PAL rev. D

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Posted (edited)

I start checking vdp with scope and those are the signals on pin 38, pin 36 (screenshot)... The only one seems with activity is pin 35 [mention=66741]ChildOfCv[/mention] do you think vdp is cooked?

523e0161a9593b2f2b35d813b96ddd3d.jpg

 

Pin 40 and 35:

 

http://imgur.com/a/Lz9QR9n

 

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Edited by hyuma

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That looks okay for a mostly black screen.  The R-Y and B-Y signals will be pretty quiet for this, except that B-Y will have a slight dip during the color burst on each line.  The Y signal shows a regular pattern of sync tips.  So there is nothing horrible about it that I can see.

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12 hours ago, hyuma said:

Ok, New cpu Z80 in place, address line now are good with activities and not stuck hi or low as before. Composite mod in place but still black screen and some green lines or dot sometimes with PAL message top right of TV that appears when I turn on the console. As I have ordered a new tms9929anl and waiting for it that arrives, just for study I should check in the old one pin 35-36 and 38?

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Did you check the BIOS again to make sure it is being accessed?  Assuming you have the 24-pin ROM chip only, that would be pin 18.

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11 hours ago, hyuma said:

Yes, pin 18 of the BIOS seems ok, I've original 24 pin ROM, the images attached are pin 1 of z80 and pin 18 of bios (A11 line)

dso_01_01_00_18_04.bmp 1.1 MB · 2 downloads dso_01_01_00_18_32.bmp 1.1 MB · 1 download

The activity on the BIOS chip looks oddly regular, but okay.

 

When the system first starts without a cartridge, it paints the splash screen and the warning message, then goes into what is essentially an infinite loop.  So when you first turn the system on or hit reset, you should see a flurry of access to the VDP for a fraction of a second, then nothing.

 

Check VDP pin 14 for such activity.  There may be a little on pin 15 too, but it's the read pin so it probably won't be a lot if any.

 

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Your scope trace is on continuous sweep.  The period for access of the VDP is less than 1/30 of a second, then quiet.  So continuous sweep isn't very useful.  A logic probe or a logic analyzer would be far better for this, since the probe would blink upon access, or the analyzer would record the bits.  Or you could put the scope on single sweep.

 

The NMI output on the VDP is pin 16.  The NMI input on the Z80 is pin 17.  Did you possibly read the wrong pins on each chip, or just post the description with the pins transposed?  Anyway, if you did accidentally read pin 17 on the VDP, that's the data bus, lowest bit.  If the processor is doing any processing, that bit should be dancing.

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Your scope trace is on continuous sweep.  The period for access of the VDP is less than 1/30 of a second, then quiet.  So continuous sweep isn't very useful.  A logic probe or a logic analyzer would be far better for this, since the probe would blink upon access, or the analyzer would record the bits.  Or you could put the scope on single sweep.
 
The NMI output on the VDP is pin 16.  The NMI input on the Z80 is pin 17.  Did you possibly read the wrong pins on each chip, or just post the description with the pins transposed?  Anyway, if you did accidentally read pin 17 on the VDP, that's the data bus, lowest bit.  If the processor is doing any processing, that bit should be dancing.


Yeah maybe I wrote wrong the description of images yes, about single sweep I don't know how to se that on scope...

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Look for trigger mode.  Right now it says "AUTO" which means it runs free if it doesn't see a trigger within some timeout period.  If it's SINGLE, it will be blank until it gets the desired trigger and then will do one sweep and hold the image.

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Look for trigger mode.  Right now it says "AUTO" which means it runs free if it doesn't see a trigger within some timeout period.  If it's SINGLE, it will be blank until it gets the desired trigger and then will do one sweep and hold the image.
This is my scope, there is trigger menu on right side, is that you meant? adc134257f0201c986668c5f4a22c2bb.jpg

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I used Single Seq button, and touched the pin 14 and 15 and seems not triggering, then I tried another pin to test it and worked than goes on stop

cad9be65f8b42ae69941251f1f79e65e.jpg

 

15780232a08cfee5467dd1eb9aaf104c.jpg

 

Seems like pin 14 and 15 doesn't triggering

 

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I started also digging on U7 74LS05N... the TL866II plus programmer allow to tests logic ICs and for the 74LS05 i have two options: 74LS05 and 74LS05 (OD). I noticed that if I choose the OD the test pass ok but if I choose 74LS05 test is failing... Does the (OD) could means "open drain" ? Anyway in the picture i posted seems like that some pins doesn't invert correctly.. Those are 2A and 2Y and 1A and 1Y..

PIN_2A_2Y.jpg

pin1A1Y.jpg

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8 hours ago, hyuma said:

This is my scope, there is trigger menu on right side, is that you meant? adc134257f0201c986668c5f4a22c2bb.jpg

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The button that says "SINGLE SEQ" is probably the one you want.

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Posted (edited)
7 hours ago, hyuma said:

I used Single Seq button, and touched the pin 14 and 15 and seems not triggering, then I tried another pin to test it and worked than goes on stop

Did you hit the reset button while touching those pins?

Edited by ChildOfCv

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Did you hit the reset button while touching those pins?
Yes I used single seq button and I press reset when I was touching pins

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Check pin 20 of the CPU in the same way.  The CPU does IO port requests to talk to the VDP, so you should see a flurry of I/O after hitting reset, then it will go quiet after setting up the screen.  So, single sweep again

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Posted (edited)
11 hours ago, ChildOfCv said:

Check pin 20 of the CPU in the same way.  The CPU does IO port requests to talk to the VDP, so you should see a flurry of I/O after hitting reset, then it will go quiet after setting up the screen.  So, single sweep again

Ok, I made single sweep and on CPU pin 20 (last 2 images). The Z80 is a new IC so i think it's working ok! I also made a continous sweep on pin 20 too (first image). 

 

dso_01_01_00_02_29.jpg

dso_01_01_00_03_13.jpg

dso_01_01_00_03_45.jpg

Edited by hyuma

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This is weird.  Pin 20 should not be active for an entire sweep period (at least 20us).  Maybe you should set the trigger to "positive"... in case it's because the chip quit driving pin 20 during the reset.

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This is weird.  Pin 20 should not be active for an entire sweep period (at least 20us).  Maybe you should set the trigger to "positive"... in case it's because the chip quit driving pin 20 during the reset.
Mmmh i have to check how to do that with my scope... I'm not sure about this option

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2 hours ago, hyuma said:

Mmmh i have to check how to do that with my scope... I'm not sure about this option

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It'll probably be the "TRIG MENU" and then one of the "F#" keys near the display.

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It'll probably be the "TRIG MENU" and then one of the "F#" keys near the display.
Those are the options for trigger menu:edcda0db130d7728f00e096a7158f610.jpgf87b1a7f925490763abbb69cd15e5941.jpg

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52 minutes ago, hyuma said:

Those are the options for trigger menu:

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Set it to "Edge triggered".  That means it is triggered when the signal crosses the trigger level.  I don't know if the other options change after setting trigger type though (they probably do--things like Video will probably add such items as "Standard (NTSC or PAL)" or "Field" or "Line").  Anyway, if the edge trigger still has the "when" setting, make it ">" and set the trigger level to about 2.5V.  Then you should be able to do a single sweep after hitting the reset button.

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Posted (edited)
4 hours ago, ChildOfCv said:

Set it to "Edge triggered".  That means it is triggered when the signal crosses the trigger level.  I don't know if the other options change after setting trigger type though (they probably do--things like Video will probably add such items as "Standard (NTSC or PAL)" or "Field" or "Line").  Anyway, if the edge trigger still has the "when" setting, make it ">" and set the trigger level to about 2.5V.  Then you should be able to do a single sweep after hitting the reset button.

Ok, I set EDGE on the trigger menu and I used the right knob "TRIGGER LEVEL" to set 2.5V. (The Edge Type  doesn't have the "when" and ">" configuration as you said). You can see the result in the image... That happens when I keep probe on pin 20 and power on the console. If I touch pin 20 with probe,  press Single Seq waiting for triggering, and press reset seems like it doesnt triggering at all... maybe the U7 doesn't work well? I checked reset signal on Z80 and it change state when press reset... 

 

pin 20 EDGE.jpg

Edited by hyuma

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3 hours ago, hyuma said:

Ok, I set EDGE on the trigger menu and I used the right knob "TRIGGER LEVEL" to set 2.5V. (The Edge Type  doesn't have the "when" and ">" configuration as you said). You can see the result in the image... That happens when I keep probe on pin 20 and power on the console. If I touch pin 20 with probe,  press Single Seq waiting for triggering, and press reset seems like it doesnt triggering at all... maybe the U7 doesn't work well? I checked reset signal on Z80 and it change state when press reset... 

Does the edge trigger have a positive/negative edge setting?  We'd be looking for positive edge.

 

In theory, at least, while U1 is in reset, pin 20 should be undriven so it should float to somewhere near 0.  Then when you release reset, it should go back to being driven and trigger that positive edge.  You can leave the scope on free running to verify this.  Now, the first I/O access may not happen within the sweep window, so it should show a 5V flat line in that case.

 

If that's the case, set the edge trigger to negative, but don't hit the single sweep button until you are already holding reset.

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Does the edge trigger have a positive/negative edge setting?  We'd be looking for positive edge.
 
In theory, at least, while U1 is in reset, pin 20 should be undriven so it should float to somewhere near 0.  Then when you release reset, it should go back to being driven and trigger that positive edge.  You can leave the scope on free running to verify this.  Now, the first I/O access may not happen within the sweep window, so it should show a 5V flat line in that case.
 
If that's the case, set the edge trigger to negative, but don't hit the single sweep button until you are already holding reset.
This is pin 20 with scope free running and after a bit I keep pressed reset button

http://imgur.com/a/EqsMxqs

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