exxos's Atari, Amiga & retro forum

HigashiJun wrote: 08 Jan 2022 12:37

rubber_jonnie wrote: 08 Jan 2022 12:26

I'm buying a Toshiba HX-10, just need to wait until February for the funds as Christmas was a bit expensive :dizzy:

This one ?

https://page.auctions.yahoo.co.jp/jp/au ... 1019469247

Yep that's the machine I'm after. Talking to one of the guys on the forum as he has one for sale.

So I'd forgotten just how solid the Aquarius was. The case plastic is quite heavy duty, and there is a metal plate in the base which adds to the weight and doubles as a heatsink for the 7805:


And the top case has more metal too to support the keyboard:


As for the mainboard, it was pretty grubby, so I gave it a clean. The underside had a lot of flux on the connectors and switch, plus the spring contacts that touch the metal base plate for RF shielding:


As for RF shielding, it is quite a bit more sensible than some contemporary machines, and overall it is a weighty little machine with a nice solid feel to it. PCB isn't the greatest, but neither is it the worst.


I'll hopefully start troubleshooting soon, but there is quite a lack of documentation, though that's never stopped me before!

A bit more digging and I found this:


Looking at the memory map, the colour information is stored in the 2nd 1K block above screen RAM, and just before user RAM.

It has 4k of RAM across 2 chips, so I need to work out which of the 2 6116's is the potential bad chip.

Looking at the schematic, and the way the character ROM is only connected to U3, and the fact that colour information is held in the first 2k block, and U3 is also labelled as VD RAM, I am taking that as a sign that that is the chip I need to replace!

I have 2 replacements on the way, but the post round here at the moment is frankly abysmal. We seem to only be getting post 3 days a week and since I am waiting on parts to actually fix things, it's rather frustrating!

Well, U3 is now socketed, and I get no display on power up with it out, so I think I have the correct IC, I just need to wait for the parts.

If they take a while, I may consider socketing U4 as well and swapping the RAM over, see if it makes a difference.

rubber_jonnie wrote: 08 Jan 2022 15:44 If they take a while, I may consider socketing U4 as well and swapping the RAM over, see if it makes a difference.

You know you want to ;)

exxos wrote: 08 Jan 2022 16:10

rubber_jonnie wrote: 08 Jan 2022 15:44 If they take a while, I may consider socketing U4 as well and swapping the RAM over, see if it makes a difference.

You know you want to ;)

I might tomorow!

exxos wrote: 08 Jan 2022 16:10

rubber_jonnie wrote: 08 Jan 2022 15:44 If they take a while, I may consider socketing U4 as well and swapping the RAM over, see if it makes a difference.

You know you want to ;)

Swapped them over, it seems like U4 is dead, as it doesn't work in place of U3. Could be both are bad.

U3 is a 6116 and U4 is a 4016, and the schematic says both should be 6116, which is what I have coming.

rubber_jonnie wrote: 09 Jan 2022 11:30 Swapped them over, it seems like U4 is dead, as it doesn't work in place of U3. Could be both are bad.

U3 is a 6116 and U4 is a 4016, and the schematic says both should be 6116, which is what I have coming.

Oh wow 6116 RAM used to be on most of the z80 systems I used to work on.

exxos wrote: 09 Jan 2022 11:38

rubber_jonnie wrote: 09 Jan 2022 11:30 Swapped them over, it seems like U4 is dead, as it doesn't work in place of U3. Could be both are bad.

U3 is a 6116 and U4 is a 4016, and the schematic says both should be 6116, which is what I have coming.

Oh wow 6116 RAM used to be on most of the z80 systems I used to work on.

The Aquarius is Z80 based, so that fits in nicely 😁

6116 and 4016 datasheets acquired, all pins match which is good, so I'll get the 'scope out and see if I can see what's going on on the address/data lines since the 4016 should be able to replace the 6116 (Both are 200ns), but it doesn't work.