We welcome retro users & hardware gurus alike! Come and join the party :)
https://www.exxosforum.co.uk/forum/
We'll see if that's the case once the DCU arrives from UK to my place... I'll let you know.czietz wrote: 09 Jul 2021 10:50I did not test this on my TT, but I find it plausible that a missing SCSI DCU might cause a bus error while TOS is trying to boot from SCSI.
Thank you for the tip, that sounds great. Unfortunately 27C010 EPROMs are now harder to get and I don't have a working EPROM burner... But I'm thinking of changing the TOS to english as the current EPROMs have 'NETH-FR' on them (Netherlands / French?), which are not languages I speak ;) If I'll get my hands on EPROMs and burner, I'll try the EmuTOS, too.czietz wrote: 09 Jul 2021 11:30 In case you have a way to program custom TOS ROMs for your TT, there's another approach you might be interested in trying: EmuTOS (512k ROM version, of course). EmuTOS gives much better error messages than Atari TOS's bombs which might help pinpoint misbehaving hardware. Also, EmuTOS can be custom-built to not use use certain hardware, such as e.g. SCSI.
Sounds like the reset circuit needs a recap. Same problem happens on the STE etc. I even suggest using higher values to allow the PSU to power up fully before reset happens.jookie wrote: 19 Jul 2021 09:41 I've added the MCP100-475 supervisory circuit (4.75V threshold voltage) on the PG (power good) line, removed the pull-up to 5V from that PG line, now the TT starts to boot after power on without manual reset button push.
Thank you for the info, I will look into that, too.exxos wrote: 19 Jul 2021 09:46 Sounds like the reset circuit needs a recap. Same problem happens on the STE etc. I even suggest using higher values to allow the PSU to power up fully before reset happens.
Excellent work sir.jookie wrote: 19 Jul 2021 09:41 I've added the MCP100-475 supervisory circuit (4.75V threshold voltage) on the PG (power good) line, removed the pull-up to 5V from that PG line, now the TT starts to boot after power on without manual reset button push.
The DCU (UA01) arrived today, I've soldered it on the motherboard, now the TT boots to desktop without 2 bombs. I didn't test the floppy, ACSI and SCSI yet, so that will follow, but at least it turns on and boots to desktop (when bought from eBay, there was no activity, and 5 chips blocked the machine start). I'm waiting for LMC1992 (U816) to arrive to push it into socket and check if that fixes the DMA sound (which couldn't go through the original soldered LMC1992).
tt_tos.jpg
Thank you :)