exxos's Atari, Amiga & retro forum

terriblefire wrote: 21 Mar 2019 09:08 Annoyingly the spare HP1661CS on my lab floor would tell me the problem in seconds.

Spare, you say...

Seriously though, I’ll check if I know someone with a better LA, otherwise I have spare adapter PCBs and postage is cheap :)

A drawing/detailed description/photo of the modifications you made to the bus arbitration lines would be interesting...

Maximilian wrote: 21 Mar 2019 09:29 A drawing/detailed description/photo of the modifications you made to the bus arbitration lines would be interesting...

Something like this... Off the top of my head. :)

And both _hlt are now tied together?

Maximilian wrote: 21 Mar 2019 10:38 And both _hlt are now tied together?

Yep

kludge wrote: 21 Mar 2019 10:47

Maximilian wrote: 21 Mar 2019 10:38 And both _hlt are now tied together?

Yep

Does diagrom do any serial output with the DIP68000 removed. Thats the first thing to check.

terriblefire wrote: 21 Mar 2019 11:36 Does diagrom do any serial output with the DIP68000 removed. Thats the first thing to check.

Crap. Yeah, that needs to be checked. Will try tonight.

Got some pointers from Edu Arana in PM as well that I will check out.

terriblefire wrote: 21 Mar 2019 11:36 Does diagrom do any serial output with the DIP68000 removed. Thats the first thing to check.

Without the DIP64 CPU in the adapter the machine is dead. So far so good.

Edu Arana suggested to me that I should try pulling the PLCC BR low and the DIP64 BR high as the only modifications. Tried it, and it seems somewhat better. Still weird results, but a bit more repeatable, and I got some other things (graphics!) on the screen.

Still not booting though.

Could this be the problem?
In the a600 the BR is tied to VPA and those are tied to a 1k resistor.
So if you pull down BR you are also pulling down VPA......not a problem during startup but maybe during normal running?

Also the 1k pullups are a lot stronger then the 470/4k7 ohm resistors on the A500.