Page 1 of 1

MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 3:09 pm
by Yod801
I've got a MegaST2, which isn't properly working. When I switch on the machine, I only have a black screen. When I switch it on with the floppy drive disconnected, there is a flickering screen for a couple of seconds before it goes black.
However when I shortcircuit pin 17 and 18 of the CPU, it'll boot, but there are no icons on the desktop while the menu works correctly.
Someone before me soldered a mod ontop of the CPU as you can see in the picture below:
Image

Please help. What can I do to solve this issue?

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 3:12 pm
by Yod801
I forgot:
Pin 18 shows 5Volts on a multimeter
Pin 17 just 0Volt

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 3:20 pm
by Atarian Computing
The mod is a factory installed blitter patch.

Clearly you already suspect the reset circuitry. Have you tried checking U2 7407?

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 3:32 pm
by Yod801
Sorry, I'm a n00b to hardware and electronics...

what is "U2 7407"? And what to check?

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 3:49 pm
by exxos
Broken reset switch ? Check RESET with meter to GND and press and hold reset button.. voltage should change between 0V and 5V.

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 4:10 pm
by Yod801
Tried to. Reset switch seems to be broken. What to do now?

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 4:16 pm
by exxos
Yod801 wrote:
Mon Jul 02, 2018 4:10 pm
Tried to. Reset switch seems to be broken. What to do now?

Replace the switch ?

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 4:21 pm
by Yod801
How? Do you sell any switches? Let's say, I don't necessarily need the switch. Can I just remove it?

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 4:35 pm
by rubber_jonnie
Yod801 wrote:
Mon Jul 02, 2018 4:21 pm
How? Do you sell any switches? Let's say, I don't necessarily need the switch. Can I just remove it?
You mentioned earlier that you weren't too great with electronic stuff and hardware, so don't do this if you aren't competent at soldering.

Exxos has switches here: https://www.exxoshost.co.uk/atari/last/storenew/#0114

Re: MegaST2 won't start up properly

Posted: Mon Jul 02, 2018 4:37 pm
by Yod801
Don't worry, my neighbour studied physics and technical computer science. He'll make it. Ordered the switch