Checked the soldering, of the ROM sockets and they seems ok.
Both of ROM chips were removed and I've checked their contents. BASIC is revC (8kB), OS is REV-02 (16kB). Checked several times with my eprom burner (TL866CS) and they contained what they should. (ROM images are from here http://atari.vjetnam.cz/index.php?frame=roms, I guess they are OK).
For being sure, I took out the CPU and re-seated it.
Checked the continuity in the socket (seated ROM pin with CPU pin), all seemed fine.
Started my 600XL, no change. 10 goto 10 fails this time with error 12..
Started up a memory test and on the third round the first ROM bar turned to red...
Which one is the first ROM? In the service field manual I just read that the memory test should not be running more than 7 minutes, because of high risk of the image burning into my monitor, but it is not written, which bar is which ROM (and both of them described as 8kB ROMs)..
I dared to left the test running - I live my life dangerous and don't care about burnt monitor displays - while I was typing this reply. Both of the ROM bars became red.
I think the RAMs are fine, at least they are green, DelayLine (RAS, CAS) should be OK.
I wrote two 28C256's and executed the test again.. Well, when the OS was replaced with a 28C256 (2x 16kB, rev-02), the 600XL didn't boot.
When only the BASIC was replaced with a 28C256, the machine booted, but with the same symptoms. After a few minutes of memory test left ROM bar turn to red, simple basic infinite loop stops with an error after 1-2 secs.
(images were taken with original chips)
- I will replace the RAMs with 4464's (41464)
- new sockets for the ROMs and try to pursue my a fellow 600XL owner to lend me some of his ROM chips to test.