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Does anyone have experience with the Ram/Rom replacement on pcbway.

M

mudmin

Experienced Member
Joined
Jan 5, 2022
Messages
99
This one https://www.pcbway.com/project/shar...1_RAM_and_ROM_replacement_board_0fa555d9.html

I built 2 of them and neither are doing anything. I'm fortunate enough to be able to test in a working pet and they both act exactly as the machine does if you pull the cpu.
A few notes -
1 - I did test the 74 series chips before soldering them to the board.
2 - I didn't have an 010 rom, but I did have an 020 so I padded it
3 - I know people have wierd issues with GAL chips. I used the lattice 16v8s. The programmer said they programmed fine, but I have been bitten by gal chips a time or 2 in the past
4 - Turning the ram and rom off on the board or any combo of the sorts gives the same results. Screen garbage.
 
Did you install the yellow wire (and not the red wire)?

How have you set the switches?

When you say you padded the ROM image, what do you mean? If the ROM you have fitted is larger, I usually find it better to duplicate the image rather than 'pad' the image (unless you know exactly what the additional address line is set to).

Have you checked the pinouts of your ROM device verses what should be installed?

Dave
 
Schematics would sure make this easier.

The difference between a 010 and a 020 is the former is NC on pin 30, the latter uses it as A17. Does this board do anything with pin 30 (tie it to either +5v or ground), or just let it float?

Agreeing with @daver2 , duping the contents across both 128k halves lets you not worry either way.
 
Thanks for the replies.

I did dupe the continents and I totally missed that difference on the eprom.

I've tried a lot of combos of the switches including disabling ram and rom etc, but if the pinout on the rom is wrong, that could explain a lot. I never tried actually pulling the rom itself. I'm probably just going to find some 010, but I'll try pulling this one first
 
I wish I had schematics also. There are many similar boards out there.

Pulling the rom and disabling the rom enable switch gives the same effect.
 
mudmin said:
This one https://www.pcbway.com/project/shar...1_RAM_and_ROM_replacement_board_0fa555d9.html

I built 2 of them and neither are doing anything. I'm fortunate enough to be able to test in a working pet and they both act exactly as the machine does if you pull the cpu.
A few notes -
1 - I did test the 74 series chips before soldering them to the board.
2 - I didn't have an 010 rom, but I did have an 020 so I padded it
3 - I know people have wierd issues with GAL chips. I used the lattice 16v8s. The programmer said they programmed fine, but I have been bitten by gal chips a time or 2 in the past
4 - Turning the ram and rom off on the board or any combo of the sorts gives the same results. Screen garbage.
Click to expand...

I have built several of the original ones for both PETs and VICs and did not have any trouble at all. I didn't need any wire either.

The PCBway shared project suggests the board was updated in some way... author name removed from silkscreen is all that's obvious to me at the moment... there was a schematic/design files for Eagle released originally.

You can find the original project here:


I've got all the files if wayback didn't manage to grab everything.
 
Did you assemble the GAL JEDEC file yourself from a .PLD file, or was it provided as a binary? ( eg, .JED file ) - I saw they inferred binaries (eg, JEDEC file) but I didn't see them on the page.

Also, keep in mind with anything you build, usual troubleshooting rules still apply - eg, check with a multimeter.
 
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