16K RAM Pack photos - please add yours

[Lardo Boffin]

And a Stonechip Panda 16K RAM pack:

Close up of RAM chip:

[bola_dor]

This is about the sixth design of ZX81 RAM pack that I have seen. Each one uses a different method or different variation of design for obtaining a -5V supply. Some use a transistor oscillator driving an inductor like the Sinclair 16k RAM pack. Some use a CMOS logic chip and capacitors to do it. Some use an audio amplifier chip. IIRC, I think I have seen one using a NE555.


Mark

Microdigital and TK90X-A (Argentinian market versions at least) uses NE555 to make -5v and CZ Spectrum/Plus uses NE555 to make 12v. On the main board as all those are 16KB,

[Lardo Boffin]

This is about the sixth design of ZX81 RAM pack that I have seen. Each one uses a different method or different variation of design for obtaining a -5V supply. Some use a transistor oscillator driving an inductor like the Sinclair 16k RAM pack. Some use a CMOS logic chip and capacitors to do it. Some use an audio amplifier chip. IIRC, I think I have seen one using a NE555.


Mark

Microdigital and TK90X-A (Argentinian market versions at least) uses NE555 to make -5v and CZ Spectrum/Plus uses NE555 to make 12v. On the main board as all those are 16KB,

Can you add some photos if you any please?

[bola_dor]

Can you add some photos if you any please?

Later I ll take some. But I am talking about twhe main board RAM not the packs.. those are 16KB TS1500 clones

[jsweinrich]

I went with a perf board using wire wrap to connect it all. Flat cable from ZX81 edge connector to the perf board. Perf board also has I/O. SRAM is actually 32kx8 (MT5C2568-30).

[McKlaud]

I did a tiny board with SMD components.

[bola_dor]

This I picked up from the trash. Sold as Czerweny CZ1016, argentina, 99.99% Timex Portugal hardware but note the transistor..

[Lardo Boffin]

A SPECIAL RAMPACK by Audio Computers:

Although the board suggests it made by Solidisk.

I wonder what goes in the socket?

[XavSnap]

Seem to be a STL like card:
http://zx81.ordi5.free.fr/CartesZx81/STL/

A buzzer ?

[Lardo Boffin]

Interesting! The boards are pretty much identical apart from the green wire from the edge connector being replaced with a resistor and not having the buzzer attached.

I wonder if the buzzer requires the EPROM or just a buzzer to be physically connected?