Sinclair ZX80 / ZX81 / Z88 Forums

Finally got my hands on a running Your Computer.

I will ad the computer to the the thread regarding chip version, soon.
First i have a question:
Does the Lambda have a command, showing the available amount of RAM (internal or expand)?
Something like DIR ot CHKDSK in Windows….
Could be nice to check if the 16K RAM module is working.

No it does not.

I think you could PEEK the RAMTOP addresses.

Hej Martin

"I think you could PEEK the RAMTOP addresses."

Exactly what i did, but thought that a quicker way was possible...Thx for reply!

In this thread, a zx81 made “RAMTOP program” showing the amount of available RAM.
Works fine on my Lambda 8300 / Your Computer.
viewtopic.php?f=7&t=3876&p=47230&hilit=ramtop+8300#top

Great

Next step: save/load programs.

Dont have a mono casette recorder (anymore), so the obvious: use a laptop soundcard as casette recorder. Unfortunately without any luck.
Until now i have not had a scope on the MIC signal, but the PC recording SW shows only noise, and when SAVE- ENTER, a little change is noticed to the signal, but not looking as “data”.
Also noticed that the phono socket does not transfer the computer GROUND to the computer phono socket, so tried to connect computer ground to phono-jack cable - but this stresses the PC soundcard, so a restart is nessasary to have it running again.

Have searched the forum, for any clues, but found very little.

Is it possible to use a laptop as “casette recorder”?
Or shall i visit a second hand shop for a real casette recorder?

One important thing. Mono 3.5mm audio “jack” sockets have their contacts in different positions to stereo 3.5mm audio “jack” sockets. It’s the same with mono 3.5mm “jack” plugs and stereo 3.5mm “jack” plugs.

To be clear, a mono plug is NOT compatible with a stereo socket, and a stereo plug is NOT compatible with a mono socket.

So for the 8 bit computer end, you MUST use a 3.5mm mono “jack” plug. But at the PC/laptop end you MUST use a stereo 3.5mm “jack” plug.

I use a lead described as “3.5mm STEREO Jack Plug to 2 x MONO Jack Plugs SPLITTER Converter Cable Lead 1m” like this one.

Only connect ONE of the 3.5mm mono plugs. Leave the other one unconnected. Traditionally when only one stereo channel is being used, it’s the left channel that is used.

Also, if the Lambda 8300 / Your Computer has a similar output level as a ZX81, it will be a VERY low level signal. Hence a PC/laptop will only pick up a signal if it’s connected to a microphone level input. A line input is no good, as it is not sensitive enough.

Mark

Hi Mark

Thanks for your reply - I am aware the differnce between mono/stereo Jack plugs/sockets.

PC soundcard: stereo 3,5mm jack socket.
Your Computer: 2 phono plugs (note MIC/EAR phono sockets without gnd connection, as the case is for the monitor socket)

I used the microphone input on the soundcard, as you wrote, its more sensitive.

The 2 attached pictures shows, that no metal is covering the circular plastic outside of the phono socket in the Your Computer.
Thats why my "missing GND" question.

As I for know, do not have any programs as soundfiles, i will for now, focus on saving some code via the MIC socket to a PC soundcard.
If anyone could point to a Lambda 8300 sound file, I could try loading a program from PC soundcard to the EAR socket on my "Your Computer".

Next step will be putting a scope on ULA pin 35, and see if any data is generated at all when SAVE.

It looks like the is a ground plane beneath the EAR and MIC sockets, so it would make sense they are connected.

I'm not at home now to check my Lambda PCB.

Hi all

"The 2 attached pictures shows, that no metal is covering the circular plastic outside of the phono socket in the Your Computer.
Thats why my "missing GND" question."

Disregard this question/issue.
The computer sockets are NOT Phono, but JACK SOCKETS!
I am on the right track again and will return when further testing is done.