Black screen after tos upgrade

[Groppo91]

W104
pin 1 is going to 48 on CPU - wrong?

W102
Pin 3 is going to 48 on CPU - wrong?

W103
Pin 3 is going to 47 on CPU - wrong?

My apologies. I should not be reading schematics before coffee. Your connections are correct. My post is wrong.

Ah thank you, I am still learning how to read schematics but so far so good from all the tests

[Groppo91]

I just noticed this purple cable loose from this chip could this be an issue?

IMG_20220329_135812.jpg (195.05 KiB) Viewed 2742 times

[stephen_usher]

I wonder what hack that is. It's definitely not a factory modification.

[Groppo91]

I wonder what hack that is. It's definitely not a factory modification.

I was thinking that but then I saw a few motherboard photos on here and the cable looks like it is connected to a pin on same chip but I can't work out which one. If anyone has any knowledge of this can you let me know as I want to connect it back. Also what does it even do?

[sporniket]

Is it me, or it looks like U211 has been wrongly inserted (side with pins 8 to 14 seems shifted, with one pin 8 dangling ; side with pins 1 to 7 seems ok) ? ,

Anyway that area is different compared to my motherboard, so I can't say if U211 is originally wired like on my schematic (p12), where pins 8-13 are in fact unused (input pins 9,11,13 tied to ground, output pins 8,10 and 12 floating).

[Groppo91]

Is it me, or it looks like U211 has been wrongly inserted (side with pins 8 to 14 seems shifted, with one pin 8 dangling ; side with pins 1 to 7 seems ok) ? ,

Anyway that area is different compared to my motherboard, so I can't say if U211 is originally wired like on my schematic (p12), where pins 8-13 are in fact unused (input pins 9,11,13 tied to ground, output pins 8,10 and 12 floating).

I am not sure but it has weird pins the one just under the number u211 is joint together and I noticed part of the solder where I assumed the cable was joint to was still there in the shot. I have soldered it back on now to that one still having black screen issues with the ROM upgrade. I am still needing to test the ROM to CPU pinouts but I will have to do them another day now.

[stephen_usher]

Actually, looking at the pictures of motherboards, that pink wire should be soldered to pin 2 of the chip. (pin 2 -> pin 9)

[rubber_jonnie]

Actually, looking at the pictures of motherboards, that pink wire should be soldered to pin 2 of the chip. (pin 2 -> pin 9)

That seems sensible since pin 2 looks lifted if you zoom in.

[Groppo91]

Yeah all soldered now but still not getting any picture out of this ROM just black screen. I notice that with the original ROM that works I get floppy drive noises but nothing from the new chips. I know I still need to test between ROMs and cpu but was just an observation. Hopefully the other ROMs I purchased arrive tomorrow so I can swap them out and see if I get same issue.

[Groppo91]

I have been checking all data and address pins today between ROM and CPU but am finding an issue:

Based on the schematics provided sporniket I am finding the Address pins wrong on my board:

Pin 2 says it should be going to A16 on the CPU (pin 47) but mine seems to be going to pin 48 which is A17.
I then tested pin 3 on ROM that should be going to A15 on the CPU (Pin 46) but mine seems too be going to pin 47 which is A16.

Anyone know why I seem to be getting one out for all the address pins I have tested so far?

Also the new ROMs came and again black screen so must be an issue with my board when trying to use a 32pin ROM