exxos's Atari, Amiga & retro forum

stephen_usher wrote: 18 Jan 2023 21:02 The HCT should be the better choice anyway. The 'T' stands for "TTL Level", so it's more compatible with TTL chips. The HC ("High speed CMOS") use the lower CMOS transition voltage levels and are technically incompatible with TTL chips, drawing more current. (I can't remember which chip is stressed and will fail sooner.)

I'll have to wait and see when the HC comes, but it is what is originally called for.

HC arrived in the post this morning, and it really isn't much different to the HCT, if at all.

Power doesn't always come on right away, but I think it's good enough for a machine I don't use often, that I can reassemble now knowing the PSU does at least work to some degree.

There is one last thing I should try. There is a pull down resistor on pin 1 of the 74HC04, and it is 7K in the instructions, but I only had 6.7K available. I'm not convinced it's an issue, but I'll add another resistor (or 2!) in series to bump it up to 7K as expected. You never know, it may make a difference, but I'll do some measuring first, see what the input and output to the inverter are showing.

I'll also replace the CMOS battery when I recap the mainboard.

So, with all the parts in place and the 'new' PSU working, I set to reassemble the machine. Here it is installed:


The main part is a simple 240v-12v PSU. This then supplies a PicoPSU in the middle at the bottom for all the working voltages. The protoboard with a layer of hot glue on it (Just to be sure nothing shorts) is where the 74HC04 is located as I couldn't quite fit it in the PSU itself. There is a nice void in the middle of the machine where it can fit.

What isn't immediately obvious here is that the fan does actually pull air through the PSU module, but clearly not at a rate suitable to keep the original PSU from going thermonuclear!!!

The mainboard also got a full electrolytic recap and a new battery holder for the CMOS battery:


Finally some gratuitous shots of it on the bench with 2 Mega STs to keep it company :)


I also finally got round to testing my CDROM eject button repairs, and I'm happy to say it works brilliantly now :)

One last post on this before I wrap up. I managed to get it onto the internet this morning using one of the two NICs it has:


It doesn't work with DHCP for some reason. I could try and figure it out but for this one machine it's not worth it, so it gets a static IP.

What I won't be doing anytime soon is doing online banking or watching Netflix, it's not the fastest machine in the world, and IE4 isn't what you'd class as a secure trusted browser anymore :)

rubber_jonnie wrote: 24 Jan 2023 10:38 ...and IE4 isn't what you'd class as a secure trusted browser anymore :)

Did we ever? :lol:

derkom wrote: 24 Jan 2023 10:45

rubber_jonnie wrote: 24 Jan 2023 10:38 ...and IE4 isn't what you'd class as a secure trusted browser anymore :)

Did we ever? :lol:

Unlikely :dizzy:

I'm pretty sure that NCSA Mosaic is secure... Mostly 'cos it's HTML V1.1 and doesn't have Javascript. Not sure any web sites will work with it these days anyway.

stephen_usher wrote: 24 Jan 2023 14:08 I'm pretty sure that NCSA Mosaic is secure... Mostly 'cos it's HTML V1.1 and doesn't have Javascript. Not sure any web sites will work with it these days anyway.

It was a struggle to find working sites for sure!