Yet Another Black Screen (YABS)

[namaman]

Just checked those...they look to be spot on:

Pin 40 - 50.077 Hz
Pin 39 - 15.624 Khz

There is a lot of sync issues when timing the small CRT with my phone unfortunately. Please try to ignore that.

[Audronic]

Hmnnnn

I will have to have a think about that

Ok Last one:-

IC118 Gate Array Pin 11 should be SYNC to the Monitor (15.625 Khz)

Keep Safe

Ray

[namaman]

GA pin 11 - 15.624 Mhz
...so looks good

[Audronic]

This is the LAST one today.

I am beginning to question the Monitor (or the lead) for part of the Problem.
Do you ave an other CPC available to plug the Monitor cable into ??

Keep Safe

See you later

Ray

[namaman]

Yes...I have tried the monitor with my working CPC6128, and there is no problem. 
I don't actually think there is any issue with video sync. I think it's just the filming of the screen makes it look funky.

[McArti0]

Ok check on the oscilloscope if this noise at ROMDIS is visible on Lines D0-D7 GA (i.e. Pin14 RAMs)

Checked on pin 14 of the RAM.
Looks random, but maybe there is a repeat pattern here.
All pins basically look the same, but with variations in the repeated patterns.

Add nCAS on other channel and set trigger on nCAS.
Show on analog scope.
Try d0-d7 pin2 pin14. 

[McArti0]

Next
ROMDIS Hi, bars

Scope on IC112 pin3, pin6. There should be no negative peaks.
CRTC pin 23 There should be no positive peaks.

IO must to be off. I hope so....

[namaman]

Hopefully I've done this correctly.

(nCAS on top and set as trigger)

All the data lines basically look the same:

[namaman]

Pin 2 and 14 of the RAM

[namaman]

Next
ROMDIS Hi, bars

Scope on IC112 pin3, pin6. There should be no negative peaks.
CRTC pin 23 There should be no positive peaks.

IO must to be off. I hope so....

no reset?
and do I keep the nCAS trigger?

[McArti0]

Next
ROMDIS Hi, bars

no reset?
and do I keep the nCAS trigger?

More time per div....

[namaman]

Do I keep the trigger?

[McArti0]

no reset?

We take advantage of the fact that seeing the bars results in one memory read and two writes.
Anything else that happens is a mistake.

[McArti0]

Do I keep the trigger?

Of course

[namaman]

ok...

pin 23 CRTC - 0V
Pin 3 ic112 - 4V
pin 6 ic112 - See photo (video on digital scope in next post)

[namaman]

pin 6 ic112 (red)  nCAS trigger (yellow):

(Ignore the stopping of the scope here as the laptop it's running to is a little slow)

[McArti0]

Ok What is IORQ pin20 Z80 doing at this moment?
With ROMDIS hi and bars on screen Pin6 IC cannot be Lo and IORQ cannot be Lo NEVER!
Also check if it is really ROMEN is very common Lo.

[namaman]

Some other observations.
Doing the ROMDIS Hi is not always consistent in what I see on the video. Sometimes the "noise" moves like in the video, and sometimes the image has "noise" but is static (frozen), and once or twice I've got this (see image).
Also with the different video outcomes (above), the pulsing on Pin 6 of IC112 looks different. 

[namaman]

Ok What is IORQ pin20 doing at this moment?

not much at about 4V (a little noisy)

[namaman]

also...here are the bars in colour for your reference:

[namaman]

ROMEM:

[namaman]

Ok What is IORQ pin20 Z80 doing at this moment?
With ROMDIS hi and bars on screen Pin6 IC cannot be Lo and IORQ cannot be Lo NEVER!
Also check if it is really ROMEN is very common Lo.

Well, it looks like ic112 pin 6 is going Lo
IORQ looks basically Hi

[McArti0]

If IORQ is always Hi then pin6 and pin3 IC112 must also be always hi. You probably don't have pin4 of IC112 connected to pin20 of z80.

[McArti0]

Also remember that the socket pin holes should be soldered to the upper and lower tracks. Originally there is a connecting tube in the hole. If you destroy this connection during unsoldering then you have to solder from the top and bottom.

[namaman]

If IORQ is always Hi then pin6 and pin3 IC112 must also be always hi. You probably don't have pin4 of IC112 connected to pin20 of z80.

it's definitely connected.

I don't think I destroyed anything. Chip Removal was very clean for every chip removed so far.

* Just checked all the connections from IC112 again...all seems fine