STe went from Bombs to a white screen

[exxos]

Does pressing reset do a anything ?

[russellnash]

Do you have an oscilloscope? or even a logic probe? It would be useful to see what the CE lines are doing at the ROM.

What might be the possible causes in a situation where all the CE lines are stuck high?

[rubber_jonnie]

Do you have an oscilloscope? or even a logic probe? It would be useful to see what the CE lines are doing at the ROM.

What might be the possible causes in a situation where all the CE lines are stuck high?

/CE is active low, so if stuck high, then yes it could be an issue, but you'd need to check during boot to see if it changes at all. If it's hung after boot at a white screen and the lines are high, that may be normal.

So you need to check during power up.

[exxos]

CE depends on the CPU running. After reset it will pulse low. If there is no code execution or something goes wrong, the CPU will crash with bus error and CE will remain high.

[russellnash]

Thank you.

[hef9800]

Does pressing reset do a anything ?

It just flashes the monitor blue and goes back to white. CE line is at 4.83 volts according to my multimeter and looks it stays high on my oscilloscope even after pressing reset. I'm gonna poke around the motherboard tonight with my multimeter since I finally got some time and see if there's anything weird.

[exxos]

Considering you had bad ROM messages originally, if you can change the sockets without destroying the motherboard, then it's still possible you have simply got bad ROM sockets. Fitting turned pin types with the dualtos board would be best.

[Dlfrsilver]

Kinda sounds like a PSU problem or bad connection . Can you post a image of your motherboard and have you tried in 8mhz mode ? Have you installed the dummy CPU? Wiped the CPU & ROM pins with IPA ? Could also be bad STE ROM sockets.

Also see here viewtopic.php?p=39201#p39201

Here's a pic of the motherboard. I haven't tried 8mhz mode yet so I'll do that next. The dummy CPU is installed. I haven't cleaned the CPU and rom pins with IPA since they looked pretty clean, but eyeballing it isn't the most accurate so I'll do that. I'll check the ROM sockets. Also on the link you sent me on the STE V1 booster, the machine still doesn't boot when pressing the reset button and does the mod to the booster still apply since it looks like mine is a later version than the picture and I have an internal Blitter.

A white screen is often an indication of a ROM issue, but the usual checks apply, so power, pull socketed chips and clean the pins and sockets with IPA, tweak the PLCC sockets as I describe here: Adjusting the PLCC socket contacts

Then I'd suggest you pull the ROM switcher (I'm assuming its socketed) and check the sockets and clean.

If you have any DeOxit or Electrolube EML, spray a little on the sockets before reinserting the chips.

If possible, do the same with the booster.

If you have one, use a bench PSU for testing to rule out the PSU. You'll only need 5v as 12v is unnecessary to boot the machine.

You should also try the booster forced to 8Mhz with the dual TOS switcher removed and the old ROMs inserted, see if the machine runs fine as stock as you can get it. If you do remove the booster for socket cleaning/tweaking then try with the old CPU installed with the original ROM to try and rule out issues with the base machine.

Lastly, when I repaired an STE for someone on the forum, they had a dual TOS switcher, with 1.62 and 2.06. TOS 2.06 kept crashing, and it turned out that the Blitter is enabled by default, and the machine kept crashing, but in 1.62 it was fine as the Blitter is disabled by default. That was a bad Blitter socket and the contacts needed to be tweaked and cleaned for it to work.

I have some tools that'll work for adjusting the PLCC sockets that I can grab from work tomorrow. I ordered some DeOxit and that'll be here in a couple days and in the mean time I'll clean with IPA, put it in 8mhz mod and swap in the old parts if needed. I don't have a bench top PSU at the moment, though this would give me an excuse to break down and buy one. Unfortunately my Blitter is internal and I don't have the right soldering equipment to attempt a resolder a surface mount chip.

Thank you all for your help and I'll report back with any progress I made!


0507231250a.jpg

Hi there, i read your topic, and i have an observation to make : You say that you bought a replacement kit of capacitors from Console 5.

That's all fine, the guy is reputed for his quality kits of caps. However, i note that you did not replaced the 2 big capacitors on the motherboard.

Exxos will confirm after me, but in itself, the big capacitors have an important role, they ensure the 5v stability in the motherboard as a whole, and they also smooth the current ripple from the PSU.

The thing is that "it's useless to change the breaks on your car if your tires are dead".

otherwise said, if you replace the caps in the PSU for very good quality ones, you need also to change those on the motherboard, because you will very possibly have some problems coming.

Those big capacitors have also the bad taste of drying out and rust completely. Be sure to do that, and yes, check the roms/sockets as well.