exxos's Atari, Amiga & retro forum

This is the board as sold in the store currently.

NOTE - 2 resets switches may be included.. One is the wrong type (6 pins, not 3 pin) I couldn't be bothered to remove the 6 pins ones, so the correct 3 pin were just slotted inside the box..

The 2 oscillators & MFP are included. Most other parts can come from the store (sockets etc) and main chips, but I suggest using a old (broke) ST to use as donor chips etc

Let's get building :)

This is the minimal steps to get it booting rather than a complete assembly guide... Maybe someone else can do a more comprehensive guide..


Firstly fitting the two oscillators..

The reset switch has pi$$ed me off. As for some reason the holes are the wrong size for the switch frame :roll:

My only solution is to bend the front metal tab sideways and scratch a bit of the resist of the PCB to make a solder point.
The other back pin I did not bother with I just cut it off.

I also noticed that the left back pin could actually wear through the solder resist and short out on the track so I have bent that rear pin upwards to miss it and I will update the PCB files to correct that problem. That problem must of been there for a while and went unnoticed until just :roll:

I think the hole size thing might have happened because the holes were not part of the switch template actually just on the PCB.. I think at some point I moved all the holes to 0.3mm instead of 0.2mm (which involved a fair bit of re-routing as well) as larger holes will be stronger and can be a bit cheaper in some fab houses. Though the switch holes must have got "caught" in the resize :cry:


Also noticed the PLCC location dots on the silkscreen also seem to have fallen victim to the hole resizing :roll:

Bit more progress...

First power up - smell of burning :roll:

It seems the amp chip was soldered in upside down and it let the magic smoke out :roll:

TOS104 booted from floppy fine :)

NEW FEATURE - Built in TOS206 decoding.


To enabled it, solder the jumper pad as shown...



Move the ROM select jumper to the 104&206 decoding location.


Move the ROM bank select jumper (open for upper bank select)


Done :)


You can now just simply alter the ROM bank jumper to select TOS versions.


Not bad if there are only two relatively minor screw ups this time I guess :lol: :hide:

exxos wrote: 24 Feb 2025 16:08 First power up - smell of burning :roll:

It seems the amp chip was soldered in upside down and it let the magic smoke out :roll:

Oops! Just this board or all of them? Is it obvious on the silkscreen which is pin 1?

At least it's booting otherwise! :-)

stephen_usher wrote: 24 Feb 2025 18:19 Oops! Just this board or all of them?

I assume all of them, I don't really fancy unpacking and repackaging the whole lot to find out :)

exxos wrote: 24 Feb 2025 18:26

stephen_usher wrote: 24 Feb 2025 18:19 Oops! Just this board or all of them?

I assume all of them, I don't really fancy unpacking and repackaging the whole lot to find out :)

OK, so there's a mandatory fix for all the purchasers to do... Either use hot air on the amp or let the magic smoke out.... their choice.

stephen_usher wrote: 24 Feb 2025 18:32 OK, so there's a mandatory fix for all the purchasers to do... Either use hot air on the amp or let the magic smoke out.... their choice.

Yep, nobody will read instructions anyway, so i will just put a sticker on it to warn people about it.

The problem is that chip is a Chinese one, I don't have any stock of them here :(