Greetings

[Slartibartfast]

Just joined and thought I’d say a quick hello.

I’ve mainly been messing around with 8 bit computers and currently have a Commodore 64 (bread in version), BBC Model B and a BBC Master (heavily modified with switchable OS and RPi based Co-processor. All were non working or had faults when bought and I have managed to bring them back to life.

As I have a keen interest in making music I decided an Atari ST might be fun to own and restore so I am now the proud owner of a 520STFM which I will need advice on as it doesn’t boot - just shows a white screen.

Looking forward to the challenges ahead….

[Icky]

:welcomewave:

[sporniket]

Hello

[JezC]

Welcome to the forum!

Might be worth getting hold of a diagnostic cart & serial lead to help fault find the ST...both available from the Exxos shop (and elsewhere).

If you can give any other details (e.g. does the floppy led come on/drive spin) that might also help others advise on first steps.

Once you have it working then a memory upgrade is useful for a lot of music programs - but only once you have a working base system!

Good luck!

[Badwolf]

:swave:

[stephen_usher]

:welcomewave:

Time to buy a diagnostic cartridge. :-)

A white screen is a good sign in a way as the machine is not fully dead.

[Slartibartfast]

Thanks for the welcome folks and for the preliminary advice on troubleshooting the issue.

Not sure if I should continue this in the Hardware section or not but the issue is as follows:

White screen - no activity from the floppy drive at all - doesn't spin, light does not come on. The only light on is the power LED.

I've checked the PSU - 5V line is running at 5.127V, 12V line at 11.8V. The 5V line is a bit noisy (100mV pk-pk)

The motherboard version is C103414-001 Revision 1.1 and I have yet to find a schematic for this board

I've checked that there is an 8MHz clock signal going to the CPU.

Using my logic probe I've identified that the CPU Halt pin in low (so the CPU is stopped). I've also identified that whilst the BERR line is high, during power on there is a single low pulse which I think indicates an error in the Glue.

Any assistance in where to check next would be gratefully received. I am thinking about checing out the reset circuit next but it's under the PSU. Can I run the Atari from an external PSU with just 5V being supplied and not also the +12V?

With regards to using a diagnostics cartridge, will it work with the machine in this state or does it require the CPU to actually run?

[rubber_jonnie]

:welcomewave:

A white screen often indicates a ROM issue, but not always.

I'd start by using a bench PSU for all testing if you have one, STs will run off just 5v and it'll guarantee you do have good power.

I'd start by looking at the PLCC sockets to make sure all the contacts are good, clean chips and sockets with IPA and use contact cleaner on reassembly.

You can tweak the pins on the PLCC sockets BTW to get better contact.

Then do the same for any socketed DIP chips.

Be aware that the /HALT line can be asserted by the CPU or something else and I've hardly ever had a bad CPU, but I've had plenty of bad GLUE chips, however check all the contacts first.

Most of the machines I've seen with a white screen haven't worked with a diag cart, but it is a useful tool nonetheless and you may be able to get output from the ST serial port to a terminal.

[Slartibartfast]

Thanks for the advice.

Biggest issue with my particular motherboard is that none of the chips are socketed. Good news in some ways - means that poor socket to chip connections can be ruled out, bad news in that swapping out a fault chip (if identified as the culprit) will be laborious.

I'll fire it up on a bench PSU tomorrow and report back. I have checked to make sure all 6 ROM chips have 5V and ground connections but these are socketed, I'll remove them, clean the sockets and try again.

Given that I've now drifted off topic with regards to saying hello and introducing myself, I think I should continue this thread in the appropriate forum.

[Slartibartfast]

I’ve continuing this discussion in the Hardware Issues section under Troubleshooting STFM with white screen.