Turning on STacy only 2 times out of 10 does it start.

[Roberto]

I just wanted to give some indications for those who, like me, have faced the problem of dead lines on an LCD display and more specifically the LCD display of ATARI STacy. I state that the two rubbery and conductive bands are found only along the two longest perimeters (width) of the display, therefore looking at the display from the front, these two are found only at the top and bottom. Along the perimeter on the left (always looking at the LCD panel from the front), there is instead a plasticized plate with contacts inside; a bit like the contacts of some old Macintosh keyboards are made. the first half of the rubbery conductive band at the bottom controls 1/4 of the display just above it, the one next to it controls the other 1/4 of the display just above it. The same thing goes for the top band. The one on the left controls the 400 lines of the display. It is made (unfortunately) with different materials, the contacts tend to break; in my case I discovered that the thin film contacts were oxidized (somehow from the photo you can see something), so very difficult to fix.

If you are not as lucky as me (@derkom just sent me an original screen!), you can try to fix it, but consider that if you have dead horizontal lines, you will hardly be able to fix them (for the reasons listed above).

I just wanted to point out that heating the area around the display is not needed (indeed it can make the situation worse) and tapping the edges (at least the one on the left side), could be useful but only temporarily; if you do it decisively you will probably break other very delicate contacts of the plastic contact band.

I found a system, in case someone wants to fix their display, by putting a fairly resistant glass, at the base and above the inverted LCD display. In the lower base I placed a mirror in order to see the results. In a few minutes I was able to make all contacts. You can make several attempts without causing any damage to the pixels. The only problem is to reconstruct the contacts of the lines and to do this I recommend using conductive glue (I state that this becomes conductive after 24 hours of drying). With this conductive glue I was able to fix some contact that popped when I tried to warm up the LCD of the light panel.
So, as soon as I have some news I will post the results here

IMG_7745.jpg (407.3 KiB) Viewed 2591 times

IMG_7738.jpg (536.62 KiB) Viewed 2591 times

IMG_7724.jpg (508.92 KiB) Viewed 2591 times

IMG_7688.jpg (535.39 KiB) Viewed 2591 times

[Darklord]

Ouch, that looks rough.

Innovative solution there - good call.

Good luck with it all.

[Roberto]

Hi guys, I took a break to recharge my batteries! Now I want to continue with the arrangement of my STacy.

I wanted to focus on the fact that my STacy ALWAYS logs in and performs the entire ROM loading process, thus leading me to view the desktop, both when I use a monochrome external monitor and when I use a color one. I've noticed that if I plug in my LCD, it doesn't always BOOT properly (turns on but screen stays black without booting from floppy). This doesn't always do it, sometimes it manages to BOOT even with the LCD connected.

Returning my STacy to the initial configuration (ie without connecting the LCD display), it always turns on again.

I then tried, from this last configuration, to connect the original controller of the HD with a correctly working BLUESCSI; I found that it behaves like when I connect the LCD, i.e. it does NOT boot but remains on a white or black screen (depending on the connected monitor).

So I figured that HD controller might draw just enough power (as does the LCD display) that it wouldn't boot.
With this in mind, I connected my ULTRASATAN (which does not require the HD controller) but a power supply via BERG connector (as for the BLUESCSI) and I had confirmation of my suspicions, namely: my STacy boots correctly, just because ULTRASATAN does not require much energy to operate.

So I realized that if I connect some device that absorbs more energy than my basic configuration my Stacy fails to boot (my basic configuration that always works is: motherboard + keyboard + trackball + floppy + external monitor).

I have changed all the capacitors on the motherboard and have replaced ALL the capacitors on the PSU several times. But nothing has changed.

I also tried to use a professional stabilized external power supply (set at 16.3V), but also in this case nothing changed.

I measured the voltages of the PSU pins and they respect the canonical values.

What else could I do?

[Roberto]

Update.
I discovered that the problem occurs exactly when the computer is turned on (ie when the switch is pressed to ON), and if the STacy finds extra peripherals connected that absorb more power than expected, then it sends the CPU to Halt. So the problem OCCURS DURING PEAK IGNITION. For example, if you could plug in other peripherals after you turned on the computer, it would work fine even after a reset. I was thinking about that CPU I put... it's a 68HC000 of dubious origin, and I don't want it to be a little picky, @exxos , you told me some time ago (or maybe someone else, I don't remember) that putting a 68HC000 or a 68000 in a STacy would be the same thing. If someone can confirm I would try to buy a 68000 here from the exxos site in order to dispel this doubt.

[Darklord]

I would be very hesitant about plugging anything in to my
STacy (or any other ST) while it's powered on...

PS Aside from SD cards/USB stuff.

[Roberto]

I would be very hesitant about plugging anything in to my
STacy (or any other ST) while it's powered on...

PS Aside from SD cards/USB stuff.

You're right, it's very dangerous, I just did it as a test (I needed it) with the BlueSCSI. With this test I deduced that also the other peripherals that draw current would have behaved in the same way. I'm looking for the area responsible for the very first turn on, which should be near the ON button. My searches take me there.

[stephen_usher]

Sounds like the reset circuit is taking the machine out of reset too early, before the 5V rail has stabilised. Without the other peripherals the PSU is bringing the voltage up just about enough in time for the CPU to come out of reset.

Check the capacitor in the reset circuit and, I think it's add a bigger capacity one to slow it down. @exxos would know better about that.

[derkom]

@exxos ,you told me some time ago (or maybe someone else, I don't remember) that putting a 68HC000 or a 68000 in a STacy would be the same thing. If someone can confirm I would try to buy a 68000 here from the exxos site in order to dispel this doubt.

The Stacy came from the factory with a 68HC000. I have used plain 68000s in mine with no problem.

[Roberto]

The Stacy came from the factory with a 68HC000. I have used plain 68000s in mine with no problem.

Perfect @derkom , I think that's the next step I'll take. At the moment it doesn't make sense to get an LCD screen because I've seen that when this is plugged in, the STacy doesn't always boot. I need to fix this weird problem first.

[Roberto]

Hi everyone! Finally I managed to figure out what was the problem affecting my Atari STacy.
Sometimes it would boot, other times it would hang at a black screen (or white in the case of an external color monitor).
In the DC/DC module there are trimmers (I call them potentiometers), which adjust the output voltages of 5V and 12V.

IMG_7269.png (3.15 MiB) Viewed 2375 times

Measuring the voltages with my oscilloscope, I had 5.2V Min and 6V Max on the 5 Volt pin, and, 12.2 Volt Min and 13v Max on the 12 Volt pin.
Among other things, I would like to understand what this means.. Is the oscilloscope giving me a mathematical average of what it is measuring?

However, I increased up to 5.8 Volt min (thanks to the potentiometer) the output of the 5Volt pin and magically my STacy manages to boot and get to the Desktop even if a HD controller and the diagnostic cartridge is connected.

Now I wonder, is all this normal? Shouldn't I exactly set 5V and 12V at the output respecting the indications of the schematic? Or should I only take measurements when the computer is under load? But even in this case the voltages must be above (at least 5.8Volt), the indicated value if I want it to work correctly.