Mega ST project

[Darklord]

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...

[HigashiJun]

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..."

[Darklord]

Yes.... :)

Capture.JPG

[HigashiJun]

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

Closeup.jpeg

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...

[HigashiJun]

Ok, USB seems to work great.

USB.jpeg

USBmouse.jpeg

That is all for today.

:D

[Darklord]

Looks like it's coming along great! :)

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

Thanks.

[HigashiJun]

Yes, not bad at all...

The Lightning ST is a really nice piece of hardware.

Cheers.

[HigashiJun]

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

A side view:

Pads.jpeg

And the final picture:

VGA.jpeg

Stay tuned.

[HigashiJun]

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

Relocatorback.jpeg

... 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 to see if something changes and maybe with another relocator I bought some time ago.

[exxos]

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.