Memory IC's for PCML Q+?

[t0nyt]

Interestingly, although the layout is the same, the boards are a bit different

(also the 0k board has all the chips socketed, in 2 different colour sockets, but I'm thinking someone may of done that)

[XorA]

I see some obvious component difference on both boards, wire link vs diode, missing capacitor, and possibly missing diode on right hand board, its a bit blurry to tell.

Are you sure the rams have power supply and that wire link isnt pulling chip select to 0 or something like that?

[t0nyt]

I see some obvious component difference on both boards, wire link vs diode, missing capacitor, and possibly missing diode on right hand board, its a bit blurry to tell.

Are you sure the rams have power supply and that wire link isnt pulling chip select to 0 or something like that?

I don’t really follow as I know very little about electronics

The board with the missing capacitor and wire link is the good board

I could have another go at imaging them?

[XorA]

Swapping the PALs between boards would be an obvious test!

[t0nyt]

Hopefully this is a better image

Many thanks

[t0nyt]

Swapping the PALs between boards would be an obvious test!

Good point, will give it a go

[XorA]

Hopefully this is a better image

Many thanks


IMG_4522.jpeg

Thats much better, the hardware gurus should be able to analyse that better!

[t0nyt]

I put the PAL from the 256k in the 0k board and it became a 256k board (according to Minerva)

I couldn't get the PAL from the 0k board to work in the 256k board though (got black and white stripes or nothing)

Put the PAL's back in their original boards and 256k is 256k & 0k is 0k (as expected) so I didn't damage them it seems

But I noticed something I hadn't noticed before, the 0k PAL has 3 legs cut off...

[Pr0f]

I suspect if you 'joined the missing legs' it would work in the other board too

[t0nyt]

I suspect if you 'joined the missing legs' it would work in the other board too

It did cross my mind that putting the legs back was worth a try

Am not sure there’s enough left to be able to solder to though, but I’m willing to give it a go in the next few days