It's 600XL time!

[rubber_jonnie]

Which IC type failed the tests? I've a bunch of 74 logic at home and 2 different ways to test them so I could see if it's a generic issue with the profiles that the TL866 includes - are you using the latest xgpro release?

Yeah, the version I have is the latest, downloaded in the last week or two. Unless of course there is a newer version!

The IC that failed was a 74LS51, all of the rest of the LS ICs passed in the TL866. The new LS51s failed identically.

I suppose as it's only a 2 output device, and the datasheet has the truth table, I could easily hook one up on a breadboard and see what the results are.

[BennehBoy]

I don't have any 51's anyway :lol:

[stephen_usher]

What does the delay line do? Is it just a series of inverters?

[rubber_jonnie]

What does the delay line do? Is it just a series of inverters?

Pretty much yes, but is vitally important to the way CAS/RAS works on these machines. The XEs used the Freddie chip instead.

There is a GitHub project: https://github.com/redhawk668/Atari-CO6 ... eplacement and a replacement has been made, which I am getting.

It uses resistors and a 74LS14, so in theory I could build one, just don't have the time right now as heading up to the Wirral tomorrow.

[stephen_usher]

That's a very strange schematic. There's no input.

[rubber_jonnie]

I don't have any 51's anyway :lol:

Never mind, worth a try :)

[rubber_jonnie]

That's a very strange schematic. There's no input.

Yeah, it is weird. Also weird that on the original delay line IC, Atari cut a bunch of pins off that they didn't need, so theres only about half the legs on it.

[rubber_jonnie]

Well, my replacement delay line just arrived, let's see if that helps

[stephen_usher]

:crossed fingers: ;-)

[rubber_jonnie]

:crossed fingers: ;-)

Sadly not :( Bit of a head scratcher as to what's next, so I think back to the schematics, service manual and Google for more research.

Whilst I'm doing some figuring out, I will replace all of the boards single wipe sockets, I don't trust them to make contact properly as most feel a bit loose, and have the spares to hand anyway.

I have already changed the one for Sally and also the delay line, and since I have my desolder gun, it won't take very long at all.

Hopefully by the time I've done that I will have a plan, unless of course it fixes it!