520 STFM Problems

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English Invader
Atari maniac
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Joined: Sat Jul 11, 2009 12:54 am
Location: Hertfordshire, UK

520 STFM Problems

Postby English Invader » Tue Jul 17, 2012 11:52 pm

I have a defective STFM that I would like to repair. When I turn the power on, all I get is a black screen with a white border.

Anyone know what the problem might be and if it can be fixed?

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Joined: Tue Jan 18, 2011 12:31 am
Location: Cheltenham, UK

Re: 520 STFM Problems

Postby Dal » Wed Jul 18, 2012 3:52 pm

Try pushing all socketed IC's into their sockets.

Also try holding the reset button while starting up, then release the reset after about 5 seconds. It could be the cap that forms part of the reset circuit has gone short?
Mega"SST" 12, MegaSTE, STE: Desktopper case, IDE interface, UltraSatan (8GB + 512Mb) + HXC floppy emulator. Plus some STE's/STFM's

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Atari freak
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Re: 520 STFM Problems

Postby ST-Freakz » Thu Jul 19, 2012 7:16 pm

more likely it's the memory, seen this problem many times

you can either change all the original 256k drams or a better option if the motherboard allows it is to install a Marpet memory upgrade to bypass the original memory and it will work

hope that helps :)

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Captain Atari
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Re: 520 STFM Problems

Postby Nikolas » Thu Jul 19, 2012 8:36 pm

there may be alot of issues, making resold as you have, mmu chip die, glue chip die. Or any other chip.

First you start with psu, must be +5.00 volts and +12.00 volts
Then check somewhere if chips gets +5.00 volts on mainboard
Check if chips are getting power from PSU !

Then start to replacing/swaping chips with good ones, like mmu, cpu, glue...

Reseet chips not bad idea.
Unplug all cables from your atari, then start with reseet chips.
Tos, and all chips. Be carefull, and dont bend pins.

Use search in this forum- lots of ppl repair st by them selfs, sometimes then buy used chips (dont cost alot like max 20$) from other users to get his atari working.
If you guys expirience hardware problems.
1. Always remove chips if possible before soldering.
2. Resolder your hardware, check cables too.
3. If problem continue THEN must be faulty software.

I got 2 Atari ST
Main is stfm, with blitter, with 4 meg of ram, with 16mhz cpu + s-video and audio input to videobox, vdi out
My english may not be correct

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