exxos's Atari, Amiga & retro forum

arkadiusz.makarenko wrote: 18 Jan 2022 18:16 May I ask what is modern compatible replacement for MOS6522?

I am trying to fixmy 1541, and last thing to test is 6522.

Edit
It is W65C22N... there is even wiki website about it
https://en.m.wikipedia.org/wiki/WDC_65C22

Hi, sorry, I missed your post - you found the part - and those are the ones I bought myself directly from Mouser.

BennehBoy wrote: 27 Jan 2022 08:33

arkadiusz.makarenko wrote: 18 Jan 2022 18:16 May I ask what is modern compatible replacement for MOS6522?

I am trying to fixmy 1541, and last thing to test is 6522.

Edit
It is W65C22N... there is even wiki website about it
https://en.m.wikipedia.org/wiki/WDC_65C22

Hi, sorry, I missed your post - you found the part - and those are the ones I bought myself directly from Mouser.

Thank you.

I still struggle to get initial boot from my 1541. :D

What are chances to have both 6522 to be dead at the same time?

arkadiusz.makarenko wrote: 27 Jan 2022 11:32

BennehBoy wrote: 27 Jan 2022 08:33

Hi, sorry, I missed your post - you found the part - and those are the ones I bought myself directly from Mouser.

Thank you.

I still struggle to get initial boot from my 1541. :D

What are chances to have both 6522 to be dead at the same time?

Actually worse than you might think, I had a drive with both VIA's dead :(

What are the exact symptoms that you are experiencing? I found this guide to be really useful -> https://portcommodore.com/rcarlsen/cbm/1541/fix1541.txt

If you've got a scope, it may be worth doing the obvious checks on the CPU to ensure, clock, reset, irq, data, address are as expected.

It doesn't boot, so drive is spinning, and red light is on all the time.

I have ordered some spares including 6522s, just to check if simple chip swap would change anything.

I don't have scope, but I have Logic Probe, but it won't show me if lines levels are out of specs.
I think I have another two 7400s ICs to replace which are common cause of this issue (those test fine TL866II programmer software - but I had this issue before ICs test fine, but fail in circuit).

Then I think I will need to get scope to find what is wrong.

OK, yeah, worth walking through that guide as there's some MOS logic chips that fail pretty commonly and will prevent a boot.

PS, a cheap logic analyser would probably work quite well too.

Might be worth a quick swap out of the ROM - those fail really regularly and will also prevent a boot.

I've got some 27cxx to mask ROM adapters if you need one.

BennehBoy wrote: 27 Jan 2022 17:44 Might be worth a quick swap out of the ROM - those fail really regularly and will also prevent a boot.

I've got some 27cxx to mask ROM adapters if you need one.

Already tried that. I build adapter and tested it in c64.
I have tried to swapp cpus as well as I have few spare.

The guide I linked earlier, although helpful, is not the main one that I used, try this -> https://portcommodore.com/rcarlsen/cbm/ ... 41chip.txt

Really useful for narrowing things down - I assume you've swapped UC2 & UC3 around with one another and it's still failing to boot? More likely that the crappy MOS labelled 74 logic chips have failed than both VIA's imho.

BennehBoy wrote: 27 Jan 2022 20:07 The guide I linked earlier, although helpful, is not the main one that I used, try this -> https://portcommodore.com/rcarlsen/cbm/ ... 41chip.txt

Really useful for narrowing things down - I assume you've swapped UC2 & UC3 around with one another and it's still failing to boot? More likely that the crappy MOS labelled 74 logic chips have failed than both VIA's imho.

Yes, swapped VIAs and no change.

I am just waiting for delivery of 74 chips on board. (Nuclear option - replace all 74 logic chips just in case ;) )

arkadiusz.makarenko wrote: 27 Jan 2022 21:33 [I am just waiting for delivery of 74 chips on board. (Nuclear option - replace all 74 logic chips just in case ;) )

Been there, done that :lol: :lol:

Start with anything labelled MOS.