MegaST2 won't start up properly

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Yod801
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Joined: Mon Oct 16, 2017 12:51 pm

MegaST2 won't start up properly

Post by Yod801 » Mon Jul 02, 2018 3:09 pm

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?

Yod801
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Re: MegaST2 won't start up properly

Post by Yod801 » Mon Jul 02, 2018 3:12 pm

I forgot:
Pin 18 shows 5Volts on a multimeter
Pin 17 just 0Volt

Atarian Computing
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Re: MegaST2 won't start up properly

Post by Atarian Computing » Mon Jul 02, 2018 3:20 pm

The mod is a factory installed blitter patch.

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

Yod801
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Re: MegaST2 won't start up properly

Post by Yod801 » Mon Jul 02, 2018 3:32 pm

Sorry, I'm a n00b to hardware and electronics...

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

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exxos
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Re: MegaST2 won't start up properly

Post by exxos » Mon Jul 02, 2018 3:49 pm

Broken reset switch ? Check RESET with meter to GND and press and hold reset button.. voltage should change between 0V and 5V.
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Yod801
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Re: MegaST2 won't start up properly

Post by Yod801 » Mon Jul 02, 2018 4:10 pm

Tried to. Reset switch seems to be broken. What to do now?

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exxos
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Re: MegaST2 won't start up properly

Post by exxos » Mon Jul 02, 2018 4:16 pm

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

Replace the switch ?
4MB STFM 1.44 FD- VELOCE+ 020 STE - 4MB STE 32MHz - STFM 16MHz - STM - MEGA ST - Falcon 030 CT60 - Atari 2600 - Atari 7800 - Gigafile - SD Floppy Emulator - PeST - HxC - CosmosEx - Ultrasatan - various clutter

https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/last/storenew/ - All my hardware mods for sale - Please help support by making a purchase.

Yod801
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Joined: Mon Oct 16, 2017 12:51 pm

Re: MegaST2 won't start up properly

Post by Yod801 » 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?

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rubber_jonnie
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Re: MegaST2 won't start up properly

Post by rubber_jonnie » Mon Jul 02, 2018 4:35 pm

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
Collector of old Atari things:
800XL + Ape Warp mod, 2x 1010 cassette, 1050 + Happy mod, 65XE (128k) & XC12, SIO2SD, 2600jr, 7800 and Lynx II
Atari 520ST (1Meg) + Gotek, 1040STFM + Vortex ATOnce + Gotek, 1040STF long button floppy, 4160 STE with Gotek and ROM switcher, 4160STE with 32Mhz booster, ROM switcher and CosmosEx, not to mention various bare ST boards for testing including a PAK 68/2 :)
Plus the rest..
Amiga stuff, Mac stuff, Sinclair stuff etc...
www.electronicnothingness.co.uk

Yod801
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Re: MegaST2 won't start up properly

Post by Yod801 » Mon Jul 02, 2018 4:37 pm

Don't worry, my neighbour studied physics and technical computer science. He'll make it. Ordered the switch

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