exxos's Atari, Amiga & retro forum

Is someone have correct Jedec files for GALs ? Mine seems to be false as /EDTACK isn't on the correct pin of the U63 GAL (incorrectly pin14) :(
Thanks for your help :)

Hey silversword, you might have missed my questions earlier:
https://www.exxosforum.co.uk/forum/viewt ... =20#p57493

I am still wondering... :D

Hi Steve :) This Falcon was given to me as non working unit. It was 1 years ago. Since, i try to repair it. As i can see, no modification has been done on it.
Thanks :)

silversword31 wrote: 06 Feb 2021 20:38 When i remove the rom, i get $FFFF as Data. It's good. But, now, the cpu doesn't continue after reading $000004.... It stops after reading :(

It won’t, it’s just got ffffffff for the program counter and the same for the supervisor stack pointer. But what you’ve proved is the data lines are likely good.

Now check the ROM chip and the socket’s contacts. Get the meter out and look for voltage on the right lines and continuity in as many places as possible.

I don’t think your gals are necessarily an issue, after all you’re getting dsack asserted, else you’d never get to reading 000004.

All looking like relating to the ROM or its socket to me.

BW.

Hi everybody :)
I've replaced the socket and i've exactly the same problem. As the Dallas Chip wasn't in good condition, i removed it as i suspect that it can corrupt data... Nothing changed :( I'm lost... I wonder if i'll be able to repair this motherboard :cry:

silversword31 wrote: 10 Mar 2021 20:28 Hi everybody :)
I've replaced the socket and i've exactly the same problem. As the Dallas Chip wasn't in good condition, i removed it as i suspect that it can corrupt data... Nothing changed :( I'm lost... I wonder if i'll be able to repair this motherboard :cry:

Did you put a replacement NVRAM in? It won't boot without it (unless you have a ct60)

silversword31 wrote: 10 Mar 2021 20:28 Hi everybody :)
I've replaced the socket and i've exactly the same problem. As the Dallas Chip wasn't in good condition, i removed it as i suspect that it can corrupt data... Nothing changed :( I'm lost... I wonder if i'll be able to repair this motherboard :cry:

Can you repeat the measurement shown in this post, please? https://www.exxosforum.co.uk/forum/viewt ... =20#p57494

Does the value accessed after 0x000006 ever change? Is it still 780000 since your work?

BW.

This might seem obvious - or has been asked before - but do you have access to a 'good' machine with all working components, so you can do the swap-dance with various bits and pieces?

At the very least it can help you stay out of dead-ends, doubting parts that actually work ok.

I have had success repairing a few machines and it always helped to be able to verify all the socketed chips, ram board, psu etc. in a second machine since you no longer have to waste any attention those. I also think having increasing confidence in 'remaining possibilities' improves your ability to focus on whats left properly and not miss important details.

I know there are a ton of non-socketed ICs on the Falcon (!) but deal with the swappable stuff first. Make notes.

Then start comparing signals with the good machine, or comparing junction drops, one IC pin at a time, with the good machine. It's tedious but each step narrows things down a bit.

I have replaced a Combel in the past - once. I don't recommend it unless you have no other choice and everything else has been ruled out. It is a nightmare to resolder even if you think you know what you are doing. It can be removed with hot air, but for the new IC, each pin must be soldered by hand with a fine tip and excellent flux choice. Don't try to do it with hot air or random flux. I think this is typical approach for SMD rework of ICs but especially true in this case IMO.