Atari ST hardware problem

[revival]

Hello,

I got an atari ST in non working state and here is what is gives. Looks like some ram chips have
been put on sockets ?

Do you know what is the source of the problem ? I would love to give it a new life
thank you very much for the help

[Mug UK]

The images aren't showing up? Reupload and reattach to your original post.

[revival]

post updated sorry

[Mug UK]

post updated sorry

No need to apologise. It just helps you get our experts to help you out a bit quicker (if they can).

[mlynn1974]

A similar board is shown here:
http://www.atari-forum.com/viewtopic.php?t=28426

So this should be a 512k ST? U32, U33, U34 and U38 look as if they are a different make of memory chip from the others so maybe someone had problems with this machine in the past and replaced those chips. Is this screen shown on boot? Video memory should start at $78000 on a half-meg ST so I think that the video memory would by default occupy memory chip U45 which is the same type as the majority of RAM chips on the board.

The display pattern is very regular repeating the same line every 160 bytes so maybe check the board for any track damage. Could it be that the video shifter chip is bad if there is no obvious track damage to the motherboard?

[siriushardware]

Can't help you specifically with that fault but like mlynn1974 above I notice the socketed RAM ICs are a different brand to the original ones still fitted directly in the board. What this says to me is that someone diagnosed a RAM fault and started to change RAM ICs until the fault was fixed - at which point they stopped, or, possibly, decided to give up after already changing four RAM ICs with no change in the fault.

Those four sided sockets on the south east corner of the PCB are a common cause of trouble because their design means that the springy pins of the chip exert constant outward pressure on the sides of the chip socket, but there is no opposite and equal force acting on the outsides of the sockets, so over time the sides of the socket gradually bow outwards.

Try removing the metal clips and (carefully) removing and replacing those two chips one at a time.

I notice the shifter screening box has two bits of writing written on at different times. One is 'OK', the other is 'FS' which could signify 'Faulty Shifter'.

[derkom]

FWIW, that the RAM in U24 has also been socketed, but has not been replaced with a different chip.

[revival]

thank you very much !

[revival]

i bought a new shifter ic and will wait for it first before checking the rams

[siriushardware]

i bought a new shifter ic and will wait for it first before checking the rams

For reference, unless you happen to be a playboy millionaire, always try the things you can try which don't cost any money first, such as removing and re-seating the socketed ICs. The idea that 'FS' might mean 'Faulty Shifter' was just a pure guess.

[revival]

I know. I first swapped rams to check for any difference. Reseted the two custom chips, and even checked for the shifter ic.
All made no difference, this is why I bought a new shifter ic

[SteveBagley]

It’s almost certainly a RAM issue — the pattern you are seeing is TOS's memory test and the machine crashing out before clearing the screen. I had similar problems with an STM (see http://atari-forum.com/viewtopic.php?f=15&t=27414 ).

Steve

[revival]

Wow, thank you steve ! Let's give it a try while waiting for the shifter

[revival]

ok shifter is good and the socketed ram chips also.
time to put the other ram chips on socket...

[revival]

I put all dram chips on socckets, but it still doesnt boot. However, the behaviour seems stable. I bought not enough dram chips so I used
some I desoldered.

Does anyone knows if it can work with only 256K on lower address ? I mean at least boot