exxos's Atari, Amiga & retro forum

Despite a new PSU, still no signal ;(

No video can be bad NVRAM settings, or missing 12V on the video DAC.

thanks for the replies.
If it were one of the both, where is the problem located on the motherboard, how to fix and what elements are needed to fix them?
Thanks

exxos wrote: 02 Sep 2018 18:00 No video can be bad NVRAM settings, or missing 12V on the video DAC.

Tbh the video DAC does not need 12V but the PAL/NTSC encoder does -- if you have it (and a modulator) installed.
If the internal fan spins, then you have 12V.

CodeKiller wrote: 04 Sep 2018 08:26 Tbh the video DAC does not need 12V but the PAL/NTSC encoder does -- if you have it (and a modulator) installed.
If the internal fan spins, then you have 12V.

If 12V is missing, you don't get RGB output. Actually seems a common fault. Seems like the dac fails (cant see 12V on it, thought there was), but never bothered to really look into it much.

Not everyone has a fan installed, and just because 12V is is on the fan, doesn't mean 12V is reaching everywhere else it needs to go. Same with the 5V rail. Blown power tracks seems common.

exxos wrote: 04 Sep 2018 08:58 If 12V is missing, you don't get RGB output. Actually seems a common fault. Seems like the dac fails (cant see 12V on it, though there was), but never bothered to really look into it.

https://www.exdwh.com/data/STV8438CV.pdf
You can even check the gerbers: no 12V trace goes to the RGB DAC.

exxos wrote: 04 Sep 2018 08:58 Not everyone has a fan installed, and just because 12V is is on the fan, doesn't mean 12V is reaching everywhere else it needs to go. Same with the 5V rail. Blown power tracks seems common.

It was an answer to "is there?" not for "is everywhere?". Of course it can be blown track, but that would be highly unlikely or at least clearly visible.
But it is not the case with the 5V. It is distributed on a power plane, so only vias/leads can be damaged (locally at a chip) but no power trace (as there isn't any)