Sinclair ZX80 / ZX81 / Z88 Forums

Moggy wrote: ↑Sat Mar 11, 2023 10:10 pm Is this of any use?

OMG that's what I couldn't find anywhere!

Could I possibly ask from whence it came?

I found it stuck in the middle of this publication,some info further on to build your own 64k board.

https://archive.org/details/sq-syntax-q ... 6/mode/2up

Another schematic possibly issue one.

Moggy wrote: ↑Sun Mar 12, 2023 9:47 pm Another schematic possibly issue one.

I think the issue one diagram isn't difficult to find, I saw a version drawn with a CAD program searching this forum but again, without any of the component identifiers.

You'd have to go through the circuit manually to determine which component is which if you didn't know, so that saves a fair bit of time.

Thanks Moggy, I just hope that the wrong diode problem with my RAM pack hasn't borked the ULA.
I'd have thought that using the RAM pack with no case would mean that there wouldn't be any wobble problems.

Sinclair 16K RAM pack issue 3

Photo of mine: Component parts
[table]
[tr]
[th]Ref[/th]
[th]Value/Number[/th]
[th]Notes[/th]
[/tr]
[tr]
[td]R1[/td]
[td]100Ω ¼W 5%[/td]
[td]Carbon film[/td]
[/tr]
[tr]
[td]R2[/td]
[td]2.2Ω ¼W 5%[/td]
[td]Carbon film[/td]
[/tr]
[tr]
[td]R3[/td]
[td]2.2Ω ¼W 5%[/td]
[td]Carbon film[/td]
[/tr]
[tr]
[td]C1 to C10[/td]
[td]47nF axial[/td]
[td]Marked 473
100nF can be used as well[/td]
[/tr]
[tr]
[td]C11[/td]
[td]22µF 16V[/td]
[td][/td]
[/tr]
[tr]
[td]C12[/td]
[td]22µF 16V[/td]
[td][/td]
[/tr]
[tr]
[td]C13[/td]
[td]100µF 16V[/td]
[td][/td]
[/tr]
[tr]
[td]C14[/td]
[td]1µF 63V[/td]
[td]A multilayer ceramic type can be used, voltage 50V.[/td]
[/tr]
[tr]
[td]C15[/td]
[td]1µF 63V[/td]
[td]A multilayer ceramic type can be used, voltage 50V.[/td]
[/tr]
[tr]
[td]D1[/td]
[td]BA157[/td]
[td][/td]
[/tr]
[tr]
[td]D2[/td]
[td]1N4002[/td]
[td]Or 1N4003 to 1N4007[/td]
[/tr]
[tr]
[td]D3[/td]
[td]1N4148[/td]
[td][/td]
[/tr]
[tr]
[td]D4[/td]
[td]BZY88C12[/td]
[td]Zener, any 500mW 12V should be okay[/td]
[/tr]
[tr]
[td]D5[/td]
[td]1N4002[/td]
[td]Or 1N4003 to 1N4007[/td]
[/tr]
[tr]
[td]D6[/td]
[td]1N4148[/td]
[td][/td]
[/tr]
[tr]
[td]D7[/td]
[td]1N4148[/td]
[td][/td]
[/tr]
[tr]
[td]D8[/td]
[td]BZY88C5V1 zener [/td]
[td]Zener, any 500mW 5.1V should be okay[/td]
[/tr]
[tr]
[td]TR1[/td]
[td]ZTX750[/td]
[td]Use a ZTX751 or ZXT753 as a replacement.[/td]
[/tr]
[/table]

Mark

1024MAK wrote: ↑Mon Mar 13, 2023 9:14 pm Sinclair 16K RAM pack issue 3

Photo of mine:

Thanks Mark, your 'raw' version of the table seems to have come out too!

sP1d3r wrote: ↑Tue Mar 14, 2023 10:09 am Thanks Mark, your 'raw' version of the table seems to have come out too!

That’s provided ready for when the forum software will correctly process tables.

Mark

I've rewired the PCB and I'm hoping to get some parts for it so I'll be able to test it soon.

I've gone over the PCB with a continuity tester now, the transistor and RAM chip are fitted so hopefully it'll be working.

Since the cannibalised issue 3 RAM pack came into my possession, I've found an old issue 2 or Timex Sinclair 1016 RAM pack which although it has the same logic as the issue 3 version, has a substantially different configuration.

The issue 3 version is a single PCB version of the issue 2, which has no ULA but instead several chips on an additional PCB in addition to the DC-DC converter and the array of 4116 memory chips.

Because of the replacement of the memory array manipulation chips with a ULA in the issue 3, it's not possible to modify an issue 3 RAM pack in the same way as an issue 2, which can be expanded to 64K using 4164 chips by piggybacking some extra array manipulation chips on the additional PCB.

More on this soon!