STacy reset problem/mandatory fixes?

[Darklord]

Okay, so I think I'm seeing the "reset" problem listed in the Mandatory Fixes section
on my STacy.

With everything enabled, Pak 030 accelerator etc., when I turn it on from a cold
state (off for hours), occasionally, I'll get video that will randomly flicker and a
few other problems like programs being unstable. After some time, and I'm assuming
everything warms up good, it becomes rock solid. A reset right after booting up cold
pretty much has the same effect and solves the problems as well.

With the Pak 030 board disabled and booting up to a stock TOS v1.4 and 8mhz 68000,
it doesn't seem to do this, even from a cold boot.

I'm assuming the extra load stresses the system more?

This machine has a new, replacement 80w Pico P/S so recapping the PS shouldn't be a part
of the problem. I also tested the 12v and 5v output of the Pico and it seems to be fine.

So I ordered some 47uf/63v and 22uf/63v capacitors. I can't seem to find C100 and C102
on my STacy's motherboard like what's listed in the Reset Problem section of the Mandatory
Fixes listing though.

I'll attach a picture of the STacy's motherboard here - as I'm terrible at reading schematics
etc, can someone point me in the general direction of these 2 capacitors?

Thanks much.

STacy Motherboard (top).jpg

[Darklord]

So I've got a spare STacy motherboard (actually, I think I've got a couple) and I took
a few pictures of the blue colored capacitors on board.

Anyone care to make a recommendation about which one(s) might be the cause of
the problem I described in the first post? In the last picture, the cap is located on
the STacy's daughter-board that holds the RAM and TOS chips.

Thanks all.

Stacy caps 01.JPG

Stacy caps 02.JPG

Stacy caps 03.JPG

Stacy caps 04.JPG

Stacy caps 05.JPG

Stacy caps 06.JPG

Stacy caps 07.JPG

Stacy caps 08.JPG

Stacy caps 09.JPG

Stacy caps 10.JPG

[exxos]

C2,C3 if the schematic is correct.

Capture.PNG

[Darklord]

Thanks much! :)

So the next question is, should I replace those with the original values
or change them?

[Darklord]

Okay, I'm starting to have some doubts about my initial assessment.

I just recently noticed that if I have the SC1224 monitor hooked up
to the external monitor port on the STacy while booting up and it
does the flicker on the replacement LCD, it does *not* do the flicker
on the SC1224.

If it was the reset problem listed in the Mandatory Fixes section.
shouldn't it affect both screens?

I'll try to get a short video of it later. It doesn't exhibit the problem
if I boot the STacy up on a daily basis. It's only after it's set for a few
days without powering on.

Thanks.

[exxos]

I'm not familiar with the STacey, but if it is only flickering with one screen, then I would assume that screen may be struggling with the resolutions & just simply be borderline specification to working, like a lot of LCDs are..

If you had reset problems then the machine would literally be resetting continuously, or at least crashing.

[Darklord]

That seems to make sense but it still leaves me puzzled.

For example, if I boot up in plain/straight/compatibility
mode, in other words, 8mhz 68000, TOS v1.4, etc, it never
does this, cold-hot-lukewarm, etc,...

Also, if it is just the RGB2HDMI mod and screen trying to
cope with ST med-res, then why would it only do it when
it's cold or been powered off for a few days?

I mean, the configuration on the RGB2HDMI mod is saved,
and that's what it reads at bootup so it's confusing to me
that it would read it cold and go "Er...no...flicker,flicker"
but then read it warm and say "Aha! Good to go!". :)

Maybe my STacy is finally just getting old and cantankerous,
like me...what do I know? :lol:

[Darklord]

Okay, here's a short video showing what my STacy is doing at bootup
(notice that there's no problem on the video feed to the SC1224):





And here's a short video showing my STacy just a very few short minutes
after the video above - and everything working perfectly!

[Steve]

Your problem isn't anything to do with the Stacy. The problem is the LCD synchronizing with the RGBtoHDMI. My monitor does exactly the same thing with my RGBtoHDMI. It's just a slightly weird off-spec signal I think.

[Badwolf]

Is this the vsync pulse issue that commonly affects SCART TVs?

I'm not sure how the RGB2HDMI is wired up.

Christian has a good write up here:- https://www.atari-forum.com/viewtopic.p ... 91#p378891

The good news is the fix is probably very easy if it's this.

BW