exxos wrote: ↑

Sun Sep 27, 2020 9:46 pm

Takes years to be this good

I thought it took "SEGA" ...sorry obscure reference to the old TV adverts

exxos wrote: ↑

Sun Sep 27, 2020 4:14 pm

There's a rule that every board has to have at least 1 bodge wire

Just seen the post about the A3 fix...which makes your comment above seem strangely prophetic!

PhilC The trick for me was to trim some 'rubbish' from the end of the image (some comment in the binary about the brutal end... which was present in more than one place!) Without doing that, the files were too big for the pair of 27C512 EPROMS I had (courtesy of rubber_jonnie)...but they may fit in...

@exxos No pressure intended

The adaptors are £12 for the exxos store but you also need a decoder for 256k Roms. Either that or two 32 pin to 28 pin adaptors and burn the boot rom that Agranlund used to load too from hard disk or floppy? The Boot ROM image from agranlund is 192k, so another option might be to use 6x 27C256 EPR...

exxos wrote: ↑

Sun Sep 27, 2020 2:50 pm

I think there is just the LS02 and MAX238 not fitted.

Great... should be a much easier build than the H4 then!

Awaiting your BOM with interest...and hope there aren't any more issues with the boards!

Looking good - looks as if the MFP in the PLCC package is pretty much the only package change (other than the various logic/level shifters...most of which will be pre-fitted)?

True...but there are lots of inherent noise issues with the older boards as well, so mixing older/aged ICs with the extra noise can easily tip the old boards from (just) working to giving lots of problems/unreliability. It's pretty impressive how many of these 30+ year old computers work at all - I ...

Welcome on board!

Glad to hear that you sorted it out...though all these problems are one of the major driving forces behind the H4/H5 etc.

I've already seen how diagnosing one or two faulty machines can take more time than building the H4...