Atari 520 ST screen corruption

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giulio
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Atari 520 ST screen corruption

Post by giulio »

I have turned on an Atari 520 ST and that is what i see, nothing else happens, the floppy doesn't work.

Is it a common problem? What should i do? ( i have some other Atari machines anyway, but i was just curious, maybe it's only a loose chip on the motherboard ).

Thank you in advance.
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Desty
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Re: Atari 520 ST screen corruption

Post by Desty »

Haven't seen this kind of corruption before, but hanging with a weird semi-random graphical pattern usually hints at a RAM problem. Check that all the socketed chips are in properly?
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wongck
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Re: Atari 520 ST screen corruption

Post by wongck »

The universal 3inch drop fix.....
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simbo

Re: Atari 520 ST screen corruption

Post by simbo »

i think its not the shifter its showing bit patters with normal sync so its not the glue
the glue keeps sync with ram video buffers via vsync so its more likely the mmu / memory has a problem
{check any ram upgrades like marpet etc are seated right} or replace the mmu/ram ic's
i dont think its the shifter as its still shifting hence the blocks of black and blue
and distinct bit pattern it shows lack of physical ram addressing

dont ever 3" drop an atari you risk fracture of the tight placed resistors
they simply split in half and compund the issues

refit the mmu or replace the ram and or mmu

but as the whole video frame up appears aok
its gota be the ram and i recond just one ic the ones used the most
can it be tried in hires mode ??this shows the exact chip...?
as a bit pattern



you can 'sometimes' open the machine
and use the back of your middle finger and test around the ram chips for heat
i use an old russian heat camera too look at chipsets got it from ng bull down in england
and a nice guy too VERY handy thing and well made
but reseat all!! chips first and retest while its appart
you can leave the psu floppy and keyboard off
just the psu and video connection is needed
but its a metal off job.. for sure...

please
while your inside the machine take some hires photos and upload them to the guides section photo gallery
as we may not have a photo of your st
dont worry we will all help get it to work im sure

another way to tell is to lift the vcc pin of each ram chip and measure its current use
i feel most failed ic's draw more or less about 10ma or so more than all or most of the rest
its easier than replacing the whole ram bank for an amature solder monkey
and its a good tip

due to the boot sequence you can tell if its ram
depends if you use a boot disk or not 19k or 192k rom
ie what type of st you have ... does it use a boot disk???

default ram chip memory is 2 bit data 8 bit address
you can see that some chips init so it must be low ram ..
becouse the hi ram is first to the 68000 to address
the fact the shifter inits and shows blocks hints at a low ram chip
ad 0 - 7
if you have a cartridge of any kind
plug it in and if the display changes then this boot part is working
this way you can track the address range thats wrong
to the exact chip ...

monitor the reset using a scope you should see a pules at power on
then another pulse
this tells you the boot block of tos is loading
1-10 below
its a very simple test using a multimeter and a few reset button presses to see the double spike
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wongck
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Re: Atari 520 ST screen corruption

Post by wongck »

simbo wrote:idont ever 3" drop an atari you risk fracture of the tight placed resistors
they simply split in half and compund the issues
OMG 8O didn't know that!!
and millions who had done this just fixed thier ST :lol:
You learn something new everyday
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dexterslab
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Re: Atari 520 ST screen corruption

Post by dexterslab »

wongck wrote:
simbo wrote:idont ever 3" drop an atari you risk fracture of the tight placed resistors
they simply split in half and compund the issues
OMG 8O didn't know that!!
and millions who had done this just fixed thier ST :lol:
You learn something new everyday
yes, i would second simbo's comments

old, big, multi-layer pcbs with smd components should be treated with the upmost respect
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wongck
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Re: Atari 520 ST screen corruption

Post by wongck »

dexterslab wrote: yes, i would second simbo's comments
old, big, multi-layer pcbs with smd components should be treated with the upmost respect
So how much longer do we have before they disintegrate?
Just 2 weeks ago my TT HDD led became dust when I touched it. :(
My Stuff: FB/Falcon CT63 CTPCI ATI RTL8139 USB 512MB 30GB HDD CF HxC_SD/ TT030 68882 4+32MB 520MB Nova/ 520STFM 4MB Tos206 SCSI
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dexterslab
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Re: Atari 520 ST screen corruption

Post by dexterslab »

wongck wrote:
dexterslab wrote: yes, i would second simbo's comments
old, big, multi-layer pcbs with smd components should be treated with the upmost respect
So how much longer do we have before they disintegrate?
Just 2 weeks ago my TT HDD led became dust when I touched it. :(
if they are left alone and treated with respect then they will (should) last a very long time. I would avoid shock, vibration and twisting of the PCB. Thankfully these boards predate Pb free solder which is far more tolerant of these effects. Pb free silver solder is much more brittle than lead solder, which is probably why simbo has to reflow PS3s and Xboxes.

The LED, yes i've had that too with the HDD and the power LED on both my TTs... i think it's something with the rubber grommet it's placed inside, over time it seems to oxidize anything around it
giulio
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Re: Atari 520 ST screen corruption

Post by giulio »

Thanks to everyone and Simbo in particular.

In the next days i'll try to open the st taking some photos, then i think you will hear something from me: the procedure seems a bit complex!!!
simbo

Re: Atari 520 ST screen corruption

Post by simbo »

you need to study the post of a very cool member

bripilot

use the search he had a similar problem with an st memory although he went through simlar phases to discover his issue
to debug first you must WRITE DOWN ON PAPER and download first the service manual for st from the guides sections
a logical story of events or non events
as you paint a picture

and was keen to try his solder iron
a great artist for sure in many ways
search his posts im sure the pics are still there
giulio
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Re: Atari 520 ST screen corruption

Post by giulio »

For now i did the high-res photos of the motherboard and so on.

I have tried pushing the chips but nothing happened.

Where can i upload them? ( as far as i've understood, in the guides section there is a kblimit of 300 )

Megaupload/Rapidshare/4shared is ok?
simbo

Re: Atari 520 ST screen corruption

Post by simbo »

there is image sharing site around like rapidshare but you can also add a snap shot to the board
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Nikolas
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Re: Atari 520 ST screen corruption

Post by Nikolas »

giulio wrote:For now i did the high-res photos of the motherboard and so on.

I have tried pushing the chips but nothing happened.

Where can i upload them? ( as far as i've understood, in the guides section there is a kblimit of 300 )

Megaupload/Rapidshare/4shared is ok?

http://imageshack.us/

try this one, pictures last for years :)
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
P.S.
My english may not be correct
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Re: Atari 520 ST screen corruption

Post by Mug UK »

The attachment size is limited to (from memory) about 3Mb per *post* not per file. So if you've got pictures in super high resolution, then it won't let you upload them. Use an app to shrink the pics to a much smaller size (I use Fotosizer on Windows for this purpose) and then try again.
My main site: http://www.mug-uk.co.uk - slowly digging up the bits from my past (and re-working a few): Atari ST, Sega 8-bit (game hacks) and NDS (Music ripping guide).

I develop a free Word (for Windows) add-in that's available for Word 2007 upwards. It's a fix-it toolbox that will allow power Word users to fix document errors. You can find it at: http://www.mikestoolbox.co.uk
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wongck
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Re: Atari 520 ST screen corruption

Post by wongck »

Nikolas/Ego wrote: http://imageshack.us/
try this one, pictures last for years :)
I use this, seems to be OK.
And yes, you need to shrink the image.
My Stuff: FB/Falcon CT63 CTPCI ATI RTL8139 USB 512MB 30GB HDD CF HxC_SD/ TT030 68882 4+32MB 520MB Nova/ 520STFM 4MB Tos206 SCSI
Shared SCSI Bus:ScsiLink ethernet, 9GB HDD,SD-reader @ http://phsw.atari.org
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