exxos's Atari, Amiga & retro forum

JezC wrote: 19 Apr 2025 13:01 Not a bad idea @PhilC...I can see if I can get the ROM out of my working H4 or the booting H5C boards and read that.

@rubber_jonnie I have some 27C4096 EPROMs but I'd have to dig out my eraser... which is hopefully somewhere in my study.... :roll:

OK, so I found some of my dual ROM images used in 27C4096 ROMs with my Mega ST and they are byteswapped, however I's still suggest you go down the road of testing using an EPROM first, even if you have to go and find your eraser, because at the last price I paid, £7, for OTP ROMs, it's worthwhile spending the time to test first.

Yes, I will try it with an old UV EPROM 27C4096 first (that's what I have in my existing H4/H5 boards anyway, it's just that they don't have 2.06 as the other image(.

I found some images you sent me a while back and that has the 1.04 with IDE support included plus 2.06 in both non-swapped and byte-swapped formats...

I'll have a look for the eraser when I finish the other tasks later today.

Thanks again @rubber_jonnie

JezC wrote: 19 Apr 2025 13:58 Yes, I will try it with an old UV EPROM 27C4096 first (that's what I have in my existing H4/H5 boards anyway, it's just that they don't have 2.06 as the other image(.

I found some images you sent me a while back and that has the 1.04 with IDE support included plus 2.06 in both non-swapped and byte-swapped formats...

I'll have a look for the eraser when I finish the other tasks later today.

Thanks again @rubber_jonnie

No problem and good luck :)

Ok, so found a few minutes to make the next step or three...

VGA connector soldered in, along with the xtal and xtal osc...

I was about to try and bodge the reset switch into the board but then I noticed that the one that came with my H5CB actually had two rows of pins in the centre...so I will have to dig out a switch from the parts for the H4 or H5B boards and see if that will fit any better...
:mad: :slapface: :pullhair: :headbang: :cussing:

Is that an unexpected issue @exxos? Or do all the reset switches now have two rows of 3 pin contacts in the centre of the switch?

Anyway, I'm out of time for now, so maybe a bit more progress at the weekend....

:sigh:

JezC wrote: 08 May 2025 21:46 Or do all the reset switches now have two rows of 3 pin contacts in the centre of the switch?

:WTF:

No idea how that happened. I buy them in lots of 100 from mouser.. :roll: I'll send u a new one...

Mine had two rows of pins too. I initially used an old ST reset switch but it was old and flimsy. I finally ended up using the two rows ones, and it fits ok. Just bend all the pins from one of the rows so they are flat agains the bottom of the switch and resting against their counterpart on the other row.
Now gently bend the pins from the remaining ow at a 45 degrees angle and solder it to the board while pushing firmly on the switch. Et voilà...

Worked fine on my 2 H5C1, if you had the bent enclosure soldered to GND, the switch is firmly seated and looks like a normal one.

ah damn, nobody said the switches were wrong :( It looks like I ordered them originally from RS, but was discontinued, so I ordered from mouser, and the wrong ones somehow.. totally different part number :roll: The ones in stock are wrong as well :roll:

I've ordered the proper switches. I will have to cut a slot in the motherboard boxes and push the new switches in when the come. I don't fancy undoing and redoing up all the motherboard boxes again.

@olivier.jan Good you managed to make them fit regardless! :thumbup: Others will have to do the same thing also.

So, a long time later and some small bits of progress.

I found that both of my remaining Hitachi 27C4096 actual EPROMs had already been programmed with the wrong images (and why can I never find the UV eraser when I need it), so I pulled one out of the H5C1 board I have built (with weird floppy issues) and checked the byte swap in that one, then programmed an OTP with TOA 1.04 and 2.06.

Then I finally dug out most of the spare parts & fitted them & robbed the last few (GLUE, MMU, 2x 6850, YM2149F) from the H5C1 build.

Well, it boots TOS 1.04 to the desktop but reports either 0 or 2 floppy drives when I have the Epson FDD (from an STE) connected...and no activity from the floppy when I try to open it.

I'll dig a bit further this evening when time allows and get some pictures up there.

It must be either a faulty component (or more than one) and/or a jumper configuration issue!

:(

What are you doing to those poor boards @JezC :(

exxos wrote: 03 Jun 2025 17:43 What are you doing to those poor boards @JezC :(

Dunno, gifted I guess.... :roll: