The latest Addition to the ST Family

[rubber_jonnie]

This is aimed at @JezC as he's been asking for pics of my 'new' Big Button STFM.

It's all really rather grubby, with all kinds of stuff in the mouse:

IMG_20210914_131500.jpg

Which now cleaned, works rather better than I had anticipated :)

Inside it's rather grubby too:

IMG_20210915_115448.jpg

And a quick peek under the hood shows it as being my least favourite motherboard:

IMG_20210915_115543.jpg

And an empty spot for the Blitter. Luckily I have a recovered socket I can fit here :)

Quite a bit of cleaning required and I'll drop a re-capped PSU in for testing purposes.

[JezC]

@rubber_jonnie Thanks for the pictures!
I've not seen that motherboard revision in a case with the long floppy button before...

Mine are all the older ones without a blitter footprint or the early 70789 revisions (so RAM under the PSU).

What are your plans for it (after the deep clean)?

[rubber_jonnie]

@rubber_jonnie Thanks for the pictures!
I've not seen that motherboard revision in a case with the long floppy button before...

Mine are all the older ones without a blitter footprint or the early 70789 revisions (so RAM under the PSU).

What are your plans for it (after the deep clean)?

That Mobo seems a bit new for a long button machine, wondering if it's a replacement?

Ideally I'll take it to 1MB, and at least add a Blitter socket. I should also decide which of my machines might get an H4 board.

[rubber_jonnie]

@JezC Some more pics for you:

Mainboard:

IMG_20210915_164031.jpg

Chinon FDD:

IMG_20210915_164055.jpg

Mainboard is surprisingly clean, and I suspect a replacement. C103253 Rev1 seems rather late to be in this machine, and though there aren't any add ons, the Shifter is socketed which is nice. The state of the mainboard just doesn't seem to match the machine, and the internal shield tabs have clearly been played with

I'll need to have a look on the underside for signs of rework, but nothing obvious at present.

[JezC]

Thanks for the additional pictures @rubber_jonnie !

Looks like all the custom chips are socketed! I think there are only one or two of those in my whole collection..most have the DMA soldered in, a few (mostly the newer ones) have the Shifter soldered in too!

With it being just the two ROMs I'm expecting you've got either TOS 1.02 or 1.04 - don't think I've ever seen the two ROM solution for TOS 1.00...but given how odd some of the combinations are out in the wild, pretty much anything is possible!

Do you have much success soldering those SMT RAMs?

[rubber_jonnie]

Thanks for the additional pictures @rubber_jonnie !

Looks like all the custom chips are socketed! I think there are only one or two of those in my whole collection..most have the DMA soldered in, a few (mostly the newer ones) have the Shifter soldered in too!

With it being just the two ROMs I'm expecting you've got either TOS 1.02 or 1.04 - don't think I've ever seen the two ROM solution for TOS 1.00...but given how odd some of the combinations are out in the wild, pretty much anything is possible!

Do you have much success soldering those SMT RAMs?

DMA is socketed too, but I was busy playing round with my Octane too and missed it!

I'll likely power it up tomorrow and run the diag cart on it to see what's what when I've cleaned up a bit more.

[rubber_jonnie]

Do you have much success soldering those SMT RAMs?

In short, no, but I reckon I could do a better job now I have more hot air experience :)

[rubber_jonnie]

@JezC

The new boy got a bit of a test drive today:

IMG_20210918_164504.jpg

But looks like we have a DMA problem, as it won't format or read floppies and doesn't see my UltraSatan either. I'll look at getting the bus resistor packs done as I have loads of spares, but as the DMA is in a socket, I suspect it may well have been replaced, so the board will have to come out and have the rework checked just to be sure.

About time I had another ST to fix!!

TOS is 1.02, I expect I'll be upgrading to 1.04 too.

[stephen_usher]

I wonder if the DMA ever gets fried by static from the port on the rear. The ACSI isn't buffered is it?

[rubber_jonnie]

I wonder if the DMA ever gets fried by static from the port on the rear. The ACSI isn't buffered is it?

I think it is directly connected, so no buffering. The ACSI socket is not great either TBH, so I may swap it out as I have spares. It is pretty much stock dead DMA territory IMHO, but I do have some spares I think. Last time I had FDD problems, on a Mega IIRC, that was a DMA too. As I mentioned, it's socketed, so I will give that a good look over.