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 »

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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Joined: Mon Oct 16, 2017 12:51 pm

Re: MegaST2 won't start up properly

Post by Yod801 »

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 »

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 »

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 »

Broken reset switch ? Check RESET with meter to GND and press and hold reset button.. voltage should change between 0V and 5V.
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
Yod801
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Re: MegaST2 won't start up properly

Post by Yod801 »

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 »

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

Replace the switch ?
https://www.exxosforum.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxosforum.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~
People should find solutions to problems, not find problems with solutions.
Yod801
Posts: 12
Joined: Mon Oct 16, 2017 12:51 pm

Re: MegaST2 won't start up properly

Post by Yod801 »

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 »

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.exxosforum.co.uk/atari/store2/#0114
Collector of many retro things!
800XL and 65XE both with Ultimate1MB,VBXL/XE & PokeyMax, SIDE3, SDrive Max, 2x 1010 cassette, 2x 1050 one with Happy mod, 3x 2600 Jr, 7800 and Lynx II
Approx 20 STs, including a 520 STM, 520 STFMs, 3x Mega ST, MSTE & 2x 32 Mhz boosted STEs
Plus the rest, totalling around 50 machines including a QL, 3x BBC Model B, Electron, Spectrums, ZX81 etc...
Yod801
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Re: MegaST2 won't start up properly

Post by Yod801 »

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