16K RAM pack

Discussions about Sinclair ZX80 and ZX81 Hardware
sP1d3r
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Re: 16K RAM pack

Post by sP1d3r »

Moggy wrote: Sat Mar 11, 2023 10:10 pm Is this of any use?
OMG that's what I couldn't find anywhere! :o

Could I possibly ask from whence it came?
Moggy
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Re: 16K RAM pack

Post by Moggy »

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
Moggy
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Re: 16K RAM pack

Post by Moggy »

Another schematic possibly issue one.
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SQ Syntax Quarterly 1-1_0051.jpg
sP1d3r
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Re: 16K RAM pack

Post by sP1d3r »

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.
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1024MAK
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Re: 16K RAM pack

Post by 1024MAK »

Sinclair 16K RAM pack issue 3

Photo of mine:
Sinclair 16K RAM pack issue 3
Sinclair 16K RAM pack issue 3
Component parts

Code: Select all

Ref  Value/Number  Notes
R1   100Ω ¼W 5%    Carbon film
R2   2.2Ω ¼W 5%    Carbon film
R3   2.2Ω ¼W 5%    Carbon film

C1 to
C10  47nF axial    Marked 473, 100nF can be used as well
C11  22µF 16V
C12  22µF 16V
C13  100µF 16V
C14  1µF 63V       A multilayer ceramic type can be used, voltage 50V
C15  1µF 63V       A multilayer ceramic type can be used, voltage 50V

D1   BA157
D2   1N4002        Or 1N4003 to 1N4007
D3   1N4148
D4   BZY88C12      Zener, any 500mW 12V should be okay
D5   1N4002        Or 1N4003 to 1N4007
D6   1N4148
D7   1N4148
D8   BZY88C5V1     Zener, any 500mW 5.1V should be okay

TR1  ZTX750        Use a ZTX751 or ZXT753 as a replacement
[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
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sP1d3r
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Re: 16K RAM pack

Post by sP1d3r »

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!
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1024MAK
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Re: 16K RAM pack

Post by 1024MAK »

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
ZX81 Variations
ZX81 Chip Pin-outs
ZX81 Video Transistor Amp

:!: Standby alert :!:
There are four lights!
Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
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sP1d3r
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Re: 16K RAM pack

Post by sP1d3r »

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


Bad tracks cut back
Bad tracks cut back
Chips socketed
Chips socketed
All rear tracks ok, damaged front tracks overlaid
All rear tracks ok, damaged front tracks overlaid
sP1d3r
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Re: 16K RAM pack

Post by sP1d3r »

I've gone over the PCB with a continuity tester now, the transistor and RAM chip are fitted so hopefully it'll be working.
Circuits tested
Circuits tested
Parts fitted
Parts fitted
sP1d3r
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Re: 16K RAM pack

Post by sP1d3r »

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!
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