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Re: 16K RAM Pack photos

Posted: Fri Jun 04, 2021 5:27 pm
by Lardo Boffin
And a Stonechip Panda 16K RAM pack:

018E6CAB-E44A-4267-8781-D4FF3C449749.jpeg

Close up of RAM chip:
499DB884-7A93-4DBE-90B2-E18A221D087E.jpeg

Re: JRS 16K RAM Pack

Posted: Sat Jun 05, 2021 5:42 am
by bola_dor
1024MAK wrote: Thu Oct 24, 2019 5:19 pm 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,

Re: JRS 16K RAM Pack

Posted: Sat Jun 05, 2021 11:43 am
by Lardo Boffin
bola_dor wrote: Sat Jun 05, 2021 5:42 am
1024MAK wrote: Thu Oct 24, 2019 5:19 pm 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?

Re: JRS 16K RAM Pack

Posted: Mon Jun 07, 2021 6:50 pm
by bola_dor
Lardo Boffin wrote: Sat Jun 05, 2021 11:43 am

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

Re: 16K RAM Pack photos - please add yours

Posted: Fri Jun 11, 2021 4:28 am
by 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).
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Re: 16K RAM Pack photos - please add yours

Posted: Fri Jun 11, 2021 3:42 pm
by McKlaud
I did a tiny board with SMD components.

Image