exxos's Atari, Amiga & retro forum

Hi everyone,

Had an issue with my ST where it worked then all of a sudden it stopped, switched it off and then on again and now I just get a white screen that does not go to desktop and the drive light and drive does not do anything.

The STE has had all mandatory fixes, tracks have been check as part of this process.
It has a Dual TOS board and 4mb of RAM.
I did do a mod to the YAMAHA chip for a drive swap also

Have check the following:
Swapped with a working recapped PSU
Swapped with a working Drive
Swapped out the RAM (working also)

I get the same response when plugging in an external drive also and swapping the boot priority and also when changed from TOS 1.62 to 2.6.

My process of elimination is pointing to the YAMAHA chip as I may of got over excited of having my ST sorted and a bit of loose wire could of shorted or be shorting this chip? Does this sounds feasible?

If it is this chip can i just check the voltages with a voltage tester? (i don't) have a scope unfortunately.

Does it boot if you press the reset switch ?

friijy2001 wrote: 04 Jun 2021 08:07 It has a Dual TOS board and 4mb of RAM.

If those are PAL TOS, can you see if your screen says you're in 50 or 60Hz? If 60, and your TOS is non-US, I would suspect the ROM board.

/Troed

The ST will boot without the Yamaha chip, I had a Mega that came without one and it booted to desktop just fine, but I should still check the area where you were working for shorts with a magnifying glass.

Check the whole board too for the same, not to mention stray pieces of wire, just in case. I doubt it's RAM, as I've never had a RAM problem show up with a white screen.

Based on your post, I doubt it is power either if you have a known good PSU.

Generally speaking, a white screen is often a ROM problem, so if you've been handling the board a lot, and it sounds like you have, the dual TOS may have a bad connection. Presuming it is socketed, I would remove and reseat the whole dual TOS adapter as sometimes the turned pin headers don't sit well in sockets.

If you have a jumper on the dual TOS for ROM selection, make sure that hasn't come off.

Bear in mind that these boards are getting old & fragile, so a lot of manhandling can break tracks and vias microscopically.

The part of my multimeter I use most is the continuity checker so you can buzz out tracks and sniff out that sort of thing.

A multimeter will only get you so far, but it will at least allow you to test that power is going to the places it should and is within voltage tolerances. Even if it has a frequency option on it, and some do, it probably won't be capable of measuring the clocks present on an ST. Don't be tempted by a £30 scope on eBay either, as they don't have the necessary frequency range. They are useful for seeing TTL signals though.

Do the basics first.

Just to add - since you have replaced the SIL resistors on the bus the chances are that one of the traces were weakened and have broken. I'd start by buzzing out those first, remember to check top and bottom traces.

exxos wrote: 04 Jun 2021 08:35 Does it boot if you press the reset switch ?

I’ll check that, good point as it could need the reset fix. Just weird it started happening all of a sudden.

Thank you everyone for your comments, will check later after work. Everything is soldered well and the tracks are fine but will double check :) glad to know it’s unlikely the Yamaha chip so will focus my attention to the dual TOS board and resistors.

Managed to get some time in yesterday to do a few more tests, to save reading the thread this is the problem...

Atari STE was working fine for a number of hours and during mid game decided to freeze, I switched it off and on and no it goes to white screen and does not go to desktop. There is only one light that comes on (not the drive light) and after the further investigation thee 68000 does start heating up, nothing bad.

The ST has had all mandatory fixes and now includes a drive swap switch and a soldered dual TOS board.

I have now tried to following:

• Swapped for a working recapped PSU, the original was the same.
• Swapped for another drive
• Tried booted from the B drive
• Swapped the 68000 (I was curious)
• Swapped the dual TOS chip
• Re-socketed any other chips
• Tried to press the reset switch

I am now onto checking tracks, I did do this previously when doing the upgrades but will check again and for any stray bits of wire.

See you on the other side! :D

Seems to be booting now but am getting this, shall I start another thread?

Video recap needed?

What changed for it to boot ? Can you post a image of your motherboard ?

There is no STE video recap kit, the only fix I did was the ghosting issue.