Mega ST project

General discussions or ideas about hardware.
User avatar
Darklord
Posts: 346
Joined: Wed Sep 20, 2017 1:41 pm

Re: Mega ST project

Post by Darklord » Tue Sep 14, 2021 1:38 am

I looked at it and don't see it there either.

Now I'm thinking it was in one of the message threads about
a "do it yourself" version of the Tweety Board and there, the
author did have a switch to go back and forth with.

I'll see if I can find it.

The Tweety Board manual/PDF does mention the problem with
digitized sounds though...
Welcome To DarkForce! www.darkforce.org "The Fuji Lives.!"
Atari SW/HW based BBS-Telnet:darkforce-bbs.dyndns.org 1040

User avatar
HigashiJun
Posts: 161
Joined: Fri Jun 19, 2020 7:21 am

Re: Mega ST project

Post by HigashiJun » Tue Sep 14, 2021 4:50 am

Darklord wrote:
Tue Sep 14, 2021 1:38 am
The Tweety Board manual/PDF does mention the problem with
digitized sounds though...
There is warning in section 6 of the document, saying:

"You may find, though, that some digitized voices may not be as clear as you would like..."

User avatar
Darklord
Posts: 346
Joined: Wed Sep 20, 2017 1:41 pm

Re: Mega ST project

Post by Darklord » Tue Sep 14, 2021 9:23 am

Yes.... :)

Capture.JPG
Capture.JPG (33.53 KiB) Viewed 475 times
Welcome To DarkForce! www.darkforce.org "The Fuji Lives.!"
Atari SW/HW based BBS-Telnet:darkforce-bbs.dyndns.org 1040

User avatar
HigashiJun
Posts: 161
Joined: Fri Jun 19, 2020 7:21 am

Re: Mega ST project

Post by HigashiJun » Sat Sep 18, 2021 3:37 am

I did not have much time this week to work on my project, but I have managed to go further on a little:

MegaST.jpeg
MegaST.jpeg (427.15 KiB) Viewed 436 times
Closeup.jpeg
Closeup.jpeg (476.96 KiB) Viewed 436 times

So far, here are the enhancements fitted in my Mega ST:

- 4 MB RAM
- Storm ST (TOS decoder and 8 MB ALT-RAM)
- Exxos Dual TOS PCB (TOS 1.04 / TOS 2.06)
- Exxos 1.44 floppy upgrade PCB
- Epson SMD-300 FDD with original Mega ST bezel
- Tweety board
- Lightning ST (IDE and USB interface)

Everything seems to work flawlessly, but is not yet fully tested.

I will have to build and try the new CPU relocator as soon as I get it from JLCPCB, as the previous one was unstable.

(I would like to thank Frank Lukas who sent me Gerber files of the new version of his relocator. Thank you Frank ! :) ).

The next steps will be:

- fit and try the USB brackets
- fit the VGA card (provided I have no issues withe the relocator)
- replace the actual recapped PSU with my STPSU
- (fit an internal CD-ROM ?)
- try to install the PAK68 and make it work

A lot of work expected...

User avatar
HigashiJun
Posts: 161
Joined: Fri Jun 19, 2020 7:21 am

Re: Mega ST project

Post by HigashiJun » Sun Sep 19, 2021 7:36 am

Ok, USB seems to work great.

USB.jpeg
USB.jpeg (365.74 KiB) Viewed 396 times
USBmouse.jpeg
USBmouse.jpeg (325.31 KiB) Viewed 396 times

That is all for today.

:D

User avatar
Darklord
Posts: 346
Joined: Wed Sep 20, 2017 1:41 pm

Re: Mega ST project

Post by Darklord » Sun Sep 19, 2021 9:24 pm

Looks like it's coming along great! :)

Gonna try and order a Lightning ST card for my Mega ST4.

Thanks.
Welcome To DarkForce! www.darkforce.org "The Fuji Lives.!"
Atari SW/HW based BBS-Telnet:darkforce-bbs.dyndns.org 1040

User avatar
HigashiJun
Posts: 161
Joined: Fri Jun 19, 2020 7:21 am

Re: Mega ST project

Post by HigashiJun » Sun Sep 19, 2021 11:40 pm

Yes, not bad at all...

The Lightning ST is a really nice piece of hardware.

Cheers.

User avatar
HigashiJun
Posts: 161
Joined: Fri Jun 19, 2020 7:21 am

Re: Mega ST project

Post by HigashiJun » Tue Sep 21, 2021 9:14 am

Few time today to do something serious and still waiting for my CPU relocator PCBs to get delivered.

I have been working a bit on the STGA board to have everything ready for fitting.

The board is insulated now with a transparent plastic film and 3 rubber pads (4cm height) are added to prevent the VGA card from leaning on the STGA PCB.

STGA.jpeg
STGA.jpeg (291.36 KiB) Viewed 308 times

A side view:

Pads.jpeg
Pads.jpeg (241.31 KiB) Viewed 308 times

And the final picture:

VGA.jpeg
VGA.jpeg (408.48 KiB) Viewed 308 times

Stay tuned.

User avatar
HigashiJun
Posts: 161
Joined: Fri Jun 19, 2020 7:21 am

Re: Mega ST project

Post by HigashiJun » Sat Oct 02, 2021 7:38 am

As yesterday was a typhoon day here in Japan and I had received my parts to build Frank Lukas' new CPU relocator, I spent my day soldering and then trying the new hardware...

Relocator.jpeg
Relocator.jpeg (324.62 KiB) Viewed 188 times
Relocatorback.jpeg
Relocatorback.jpeg (298.19 KiB) Viewed 188 times

... to discover that my Mega ST becomes unstable once the relocator fitted (like with the previous one) and no matter in which order all the other expansions were installed in the machine (relocator first then Storm St, Strom ST first then relocator, etc.).

I have bombs, resets and freezes but everything goes back to normal once the relocator unfitted. :?

I do not know if there is something related here with the original and recapped PSU being too weak or with the relocator itself.

I will have to try with my STPSU from Centuriontech to see if something changes and maybe with another relocator I bought some time ago.

User avatar
exxos
Site Admin
Site Admin
Posts: 16016
Joined: Wed Aug 16, 2017 11:19 pm
Location: UK
Contact:

Re: Mega ST project

Post by exxos » Sat Oct 02, 2021 8:18 am

The mega ST is the worst machine to update. All you can do is the mandatory fixes. Beyond that, you're fighting an unstable bus. Debugging will take a lot of time. It's why I don't support mega anymore. STFM is hard enough. It's why I designed the remake boards. If you *really* want it to work, then get a fast logic analyser like @terriblefire has and start to debug the entire bus to see where the issue is.

Edit:
I think I said before the 8mhz clock from the shifter is really bad, it needs a Schmitt buffer on it and some experiments with series resistor value. 47R is a good start.
https://www.exxoshost.co.uk/atari/ All my hardware guides - mods - games - STOS
https://www.exxoshost.co.uk/atari/store2/ - All my hardware mods for sale - Please help support by making a purchase.
viewtopic.php?f=17&t=1585 Have you done the Mandatory Fixes ?
Just because a lot of people agree on something, doesn't make it a fact. ~exxos ~

Post Reply

Return to “HARDWARE DISCUSSIONS”