Having some trouble rejoining the ST club

[Mickles]

Hi folks,

 

I picked up an AtariST 520STFM on eBay recently, it was sent from the UK to the US. I have a step transformer to 220 volts, but when I plug in the UK plug (which came with it) - it’s seems like it comes on for a bit then shuts down - if I keep trying the amount of time it comes on for keeps reducing and eventually i can’t hear it try to access the disk it just shows a dim power light. When it seems like it’s working it has a bright power light, accesses disk a couple of times (with no disk in) and then goes dim.

 

I am using a special scart cable I bought into an OSSC and then into a regular computer monitor, but I never get anything on screen. The OSSC just loses sync with the ST after a few seconds (it does see a signal on 50hz for a few seconds but I see nothing on screen)

 

The seller listed it as working, maybe something happened in transit.

 

any ideas?

 

id love to get it working it was my first computer. 
 

here is a video 

 

 

[Mickles]

Just wanted to update folks here.

 

i removed the power supply and measured the outputs at the terminal which connects to the motherboard

 

Both the 12v and 5v rail were measuring 0.5v 

 

I inspected the reverse of the board (it was a 508a Rev-0) and found several suspect solder joints. I reflowed them and tested the power supply using a 8ohm 100w loading resistor where I found both the 5v and 12v rails to be healthy.

 

after re-installing the supply the machine was fine and booted up. The end. 

[Forrest]

That’s great news!

[Mickles]

Thank you I am excited to move to the next step. This is a UK machine so it is outputting 50hz and I get a rolling black and white GEM desktop on RF.

 

is there a way for me to boot this machine to US TOS without modifying it?

 

I have a Gotek if that helps

[tjlazer]

Yes, by merely installed US TOS ROMS!

[oracle_jedi]

As @tjlazer says, you can install new TOS ROMs into your machine, and if you do so, I would suggest TOS 1.04 as it adds support for boot-from-harddisk.  The ROMS are *usually* located under the power supply, but exact locations depend on the motherboard revision.  

 

You can also find a tool called "SELTOS" which allows you load up an alternative TOS to the one in ROM.  It will however consume 192K of RAM, so if your 520STFM is stock, that won't leave you much RAM for applications.

 

Bear in mind that switching to a U.S. TOS means that some keyboard mappings will now be wrong.

 

If you merely want to switch to a 60Hz display refresh, there is utility you can download to do that, and set to auto-run on boot.

 

That said, your RF will only ever be PAL on UHF channel 36.  The composite video out will also be PAL (now at 60Hz).  The RGB output will switch to a 60Hz refresh.