Sinclair ZX80 / ZX81 / Z88 Forums

I’m so used to the ZX81 and Spectrum I never even thought for one minute to do that! Ha! How conditioned am I?! Lol Thanks, I knew it had to be fairly obvious but I never thought it would be that obvious! Lol See, I knew I was going to make a fool out of myself, still thank you for answering and at ...

On a ZX80 it shows some commands on a sticker on the case named INTEGRAL FUNCTIONS how do you enter those on the keyboard? How do you PEEK or CHR$ for example? They're not printed on the keyboard and i couldn't even find out how in the manual I read. Do I need to utter a magical incantation while wh...

Paul wrote: ↑Fri Jan 13, 2023 12:46 pm 4148
Sorry, meant 4816

PERFECT! That was exactly what I needed to know, thank you so much!

I found the pin outs here:

https://www.applefritter.com/appleii-bo ... Matrix.htm

Hi,

On the ZX81 there are three memory sockets on the Issue 3 board.

Two small memory chips in sockets IC4a and IC4b

One 24 or 28 pin chip in IC4

Does anyone have the pinout of IC4 when configured for 28 pin use? (LK2 connected)

What chip was meant for use in the 28 pin configuration?

Here is what I did: I fitted a, tested, 62256 with pulled out pins, wired them up. Links to images showing work done: https://photos.app.goo.gl/mCGRTMNBEWUPqw9u7 https://photos.app.goo.gl/q7knjv2ndxTf2M329 Here is what I got: https://youtu.be/GazbsM2r9wM Doesn’t matter how I set the memory switches,...

Paul wrote: ↑Fri Jan 06, 2023 8:41 am The manual of the vLA81 makes all this very clear.

It doesn’t answer the questions I posted or I wouldn’t have posted them.

The instructions also appeared….appeared….to contradict themselves in relation to A13 and the oscillator. So I thought it best to ask before ploughing ahead.

I’ve got myself in a right tizzy over adding this ram upgrade, can someone help me out. I’ve got a ZX81 Iss.3 At present it has a VLA81 fitted and no RAM. Works ok with a RAM Pack fitted. I have a 62256 chip, tested, working. Fitted a socket to the ZX81. I’d like 32K internally and the ability to us...

Anyone have any experience of sticking one of these down?

What’s a good modern adhesive strip that fits and sticks well?

What have you actually used on your ZX81?

I’ve now removed the new ram and put in an HM6116 in the lower part of the socket and changed the link back to LK1.

That doesn’t work either. Lol

So it’s a memory fault on the board somewhere, any tips?

16k external ram pack still works so the address and data lines must be ok. What might not be?

It depends on if the replica is wired with A0 to the A0 pin on the RAM, A1 to A1, A2 to A2 etc. Only the original Sinclair boards are not wired like this, they take advantage of the fact that it does not matter which address line from the Z80 goes to which address pin on the RAM chip, as long as th...