PCB by Franck78..

Discussions about Sinclair ZX80 and ZX81 Hardware
redhawk668
Posts: 13
Joined: Sun Jun 06, 2021 10:15 pm

PCB by Franck78..

Post by redhawk668 »

So, I bought one of the Issue 3 replica PCB's by Franck78 and I've built it. I can say it has been a satisfying experience. The board is working like a charm :D. Building it was a breeze. I took some pictures while building it. It also has my own design internal 16K modification PCB and composite mod PCB which replaces the modulator box internals.

The ULA, CPU, modulator box and 6.5 Mhz resonator are from a duff ZX81 board, the rest is brand new. I rummaged through my parts bin and found some MPS2369 transistors and a brand new 7805 voltage regulator. MPS2369 is perfect on a ZX81, as a replacement for ZTX313.

The mounting holes are lining up and it fits in a ZX81 case.

I've also compiled a BOM:

Resistors:

R1 : 10K
R2 : 680R
R3 : Not used
R4 : 18K
R5 : 330R
R6 : 2K2
R7 : 470R
R8 : “
R9 : “
R10 : “
R11 : “
R12 : “
R13 : “
R14 : “
R15 : 220K
R16 : 1K
R17 : “
R18 : “
R19 : “
R20 : “
R21 : “
R22 : “
R23 : “
R24 : “
R25 : “
R26 : “
R27 : “
R28 : 680R
R29 : 1M
R30 : Not used
R31 : Not used
R32 : Not used
R33 : 4K7
R34 : 220R
R35 : 10K
R36 : “
R37 : “
R38 : “
R39 : 10K
R40 : “
R41 : “
R42 : “
R43 : 10K
R44 : “
R45 : “
R46 : “
R47 : “

Capacitors:

C1 : 47pF
C2 : 47nF
C3 : 22uF (Electrolytic)
C4 : 47nF
C5 : 1uF (Electrolytic)
C6 : 100pF
C7 : 47pF
C8 : 47nF
C9 : 47nF
C10 : 10nF
C11 : 47nF
C12 : 47pF

IC's:

IC1 : Sinclair ULA (or equivalent like vLA1)
IC2 : Sinclair ROM (2364 or equivalent)
IC3 : Z80A CPU
IC4 : 4118 or 6116 SRAM. For 16KB internal a 62256 with some rewiring can be used too. Or my own design 16KB internal PCB.

Diodes:

D1 : 1N4148 or 1N4448
D2 : “
D3 : “
D4 : “
D5 : “
D6 : “
D7 : “
D8 : “

Transistors:

TR1 : ZTX313 or MPS2369
TR2 : “
REG : 7805 Voltage regulator or switching mode DC/DC converter

Last but not least: Modulator box
Attachments
IMG_20210614_213217_1.jpg
IMG_20210614_213140_1.jpg
IMG_20210612_225155.jpg
IMG_20210612_220106.jpg
User avatar
Paul
Posts: 1511
Joined: Thu May 27, 2010 8:15 am
Location: Germanys west end

Re: PCB by Franck78..

Post by Paul »

Thanks for sharing this.
I'm going to start building it soon and your BOM comes at a perfect time
Kind regards Paul
In theory, there is no difference between theory and practice. But, in practice, there is.
redhawk668
Posts: 13
Joined: Sun Jun 06, 2021 10:15 pm

Re: PCB by Franck78..

Post by redhawk668 »

Most of the components can be bought from Mouser or Digikey. Reichelt has the 6.5 Mhz resonator brand new. article nr. is SFE 6,5.
Orac
Posts: 27
Joined: Sat Dec 15, 2018 10:33 am

Re: PCB by Franck78..

Post by Orac »

Is it possible to get a board still?
Franck78
Posts: 12
Joined: Mon Mar 08, 2021 11:24 am

Re: PCB by Franck78..

Post by Franck78 »

"The mounting holes are lining up and it fits in a ZX81 case."


I was unsure because I don't have any ZX81

Yes I have two or three pcb.
Orac
Posts: 27
Joined: Sat Dec 15, 2018 10:33 am

Re: PCB by Franck78..

Post by Orac »

There is a resistor on the BOM that I just cannot locate on the board.

Is R40 the resistor under IC3, the Z80, it just says R, there is no number.

R41 isn’t marked either, I’m assuming it’s under R42 as that spot shows no marking at all.
Last edited by Orac on Wed Nov 17, 2021 10:12 pm, edited 1 time in total.
Orac
Posts: 27
Joined: Sat Dec 15, 2018 10:33 am

Re: PCB by Franck78..

Post by Orac »

redhawk668 wrote: Thu Jun 17, 2021 6:19 pm Most of the components can be bought from Mouser or Digikey. Reichelt has the 6.5 Mhz resonator brand new. article nr. is SFE 6,5.
Reichelt don’t seem to sell to the UK, the country is missing from their drop down lists. Farrell in the UK have the resonators though.
Orac
Posts: 27
Joined: Sat Dec 15, 2018 10:33 am

Re: PCB by Franck78..

Post by Orac »

I’m one capacitor away from completing the board……….and I ordered the wrong one! 😢😢😢😢😢

Typical! Lol

Just ordered the correct one.

I’ll be over here, crying in the corner, lol
Orac
Posts: 27
Joined: Sat Dec 15, 2018 10:33 am

Re: PCB by Franck78..

Post by Orac »

A new ZX81 was given life!

Thanks for the idea, the board and the help.

The pictures show it running and it just before it was completed with an original rom instead of its new one and no ram, couple of components missing.

No pic of it finished yet as I put it in a case to test it and I’ve not uncased it again yet.

Great little project, lots planned to do with it, watch this space as they say!
Attachments
B008BFD6-7E37-4DED-B077-3AC164FD79EB.jpeg
6CD67184-BC24-4D17-B0A0-5C2F8E7359A3.jpeg
relqasem
Posts: 7
Joined: Fri Oct 29, 2021 10:09 am

Re: PCB by Franck78..

Post by relqasem »

I would still love to get my hands on a PCB
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