STe went from Bombs to a white screen

[hef9800]

Hey everyone! My poor STe has went from bombs on the screen after running for a few hours to now a white screen and won't attempt to cycle the floppy drive. I'm hoping you all can tell me where to start since I'm a noob to diagnosing Atari STs. This is gonna be a long post so I apologize for all the reading you're about to do.

System info and mods:
Atari 1040 STe NTSC
CA4003290 motherboard
4MB non parity ram
Original floppy drive
ASP34-1 PSU
STE V1 32mhz Booster plug in (2020 release according to what is printed on it)
STE TOS Switcher with the U.K. roms installed, also have the U.S. roms for it as well
PSU recapped with a capacitor kit from Console5

So my STe was fully stock when I first got it a few years ago and fully working. I decided to squeeze some more power out of it and grabbed the 32mhz booster, TOS Switcher and the U.S. and U.K. fast roms. I installed it all and the STe booted and ran fine. Eventually I found that after it was running for about 3 hours it would start crashing and if I let it sit for a bit it would be fine for a while and then it crash again. I swapped the ram out and it made no difference. Checked the voltages on the PSU connector to the motherboard while the STe was running and got 4.9 volts on the 5 volt lines, the grounds were good and 11.3 volts on the 12 volt line. Decided to grab a PSU capacitor kit from Console5 since it couldn't hurt and easy enough to do. Still no difference and voltages were about the same. Notice that the solder joints for the keyboard broke and causing the mouse, keyboard and controller not to work properly. Resoldered that and the keyboard, mouse and controller started working again but now starting freezing when it got to the desktop. After restarting a few times it made a hum from the monitor speaker during the ram check, I shut it off and turned it on and now it just shows a white screen. I've tried reseating all the chips and swapped roms and no change. I added pics of the monitor of the bomb error screens I got as well. So now I'm stuck and looking for help on what to do next and thank you for any help you all can give!

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[exxos]

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

[rubber_jonnie]

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.

[hef9800]

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

[exxos]

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.

Thanks for the image.

What value is P100 on the bottom of the motherboard ?

Is the IC where you soldered the 32MHz wire the "F" series ?

Indeed as said before you can fit your original ROM and the booster will still work , albeit slower without the fast ROM access. But if it is stable with the original ROM, the least it helps suggest the problem is with the ROM not the CPU side of things. Though I would really suggest you try 8MHz mode first..

There may be a problem, as the version of the booster you have is actually designed to run alongside the original motherboard resistor packs. If you are stable at 8MHz then it may suggest that is the case..

You could disconnect the wire going to the ROM board is that will still run the booster at 32Mhz, but you will not get fast ROM access.. but that's fine as if that works, then you know the bus isn't stable at 32MHz for ROM access..

EDIT:

Looking at my install page here https://exxosforum.co.uk/forum/viewtopi ... =24&t=4441 it actually says remove them.. But that is actually only true if you have the 2.2K pullups on the booster.. the one you have is the same one I have running in my test machine currently and indeed the same motherboard revision.. So that could be my f**k up there sorry :(

[Chris O.]

I would probably test this STe with HARDWARE ESSENTIALS ... DIAGNOSTIC CART first. ;)

[hef9800]

The P100 is 1.2K ohms though it was 1.12K on three of the pins if that makes any difference.

Yup the IC is a SN74F257N

I tried the 8Mhz mode and still the same. Swapped in the old ROM chips and still nothing and then I tried it with the original CPU and ROM and same result.

I'll reinstall the resistor packs. That was my f-up not yours, I misread the instructions, but apparently it worked for a bit lol. I still gotta go over the ROM sockets and make sure there isn't something wrong there.

[rubber_jonnie]

I would probably test this STe with HARDWARE ESSENTIALS ... DIAGNOSTIC CART first. ;)

While the diag cart is a good option, the machine still has to get to a certain point in the boot sequence for it to run. A white screen usually means it isn't getting that far, and in all the cases I've looked at with a white screen, the diag cart doesn't work, not even when viewed through the serial port option.

@hef9800 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.

[hef9800]

I've just got a cheap $60 Yeapook oscilloscope so it may not be the best. Here's a couple pics. If I set it to full auto it doesn't see much

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but if I adjust the settings I get what I assume is noise.

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I had to order resistors and they'll be in tomorrow so hopefully that'll help. I wish there was still a Radio Shack here...

[hef9800]

So I have back to completely to stock, resistors are reinstalled, Deoxited all the sockets, ran a soldering iron over the ROM socket solder and still a white screen. The CPU does get warm and everything else that I could touch while it's on felt cool to the touch. I've got power and ground to the ROM chips so I'm assuming there's a broken trace somewhere on the board that I'm gonna have track down. Also I get a white screen with the CPU and ROM chips out of the sockets which I assume is the video chip just sending a signal with no data.