tashtwenty/pcb/TashTwenty Tiny

TashTwenty Tiny

This is a dual PCB design, using mostly through hole components (with the exeption of the SD connector). It's designed this way to be period correct and easy to build for people who don't like soldering SMT components

This folder contains the source KiKad files for the main board. Please check the DB19_IDC20 subfolder for the DB19 to IDC20 adapter.

BOM

BOM (main board)

Here is the BOM for the main board. Part number are what was tested on prototypes board but you may find alternatives easily, especially resistors and sockets

Reference(s)	Value	Quantity	Notes	Part number
C1, C2	2.2uF	2	radial electrolytic capacitors 4x1.5mm	Jamicon SHR2R2M1HC07M
C3, C4	100nF	2	ceramic capacitor 5.08mm	Weltron 453358
D1	Green	1	5mm green LED	Kingbright L-53SGD
D2	Yellow+Red	1	5mm dual color common cathode LED	Kingbright L-59EYW
J1	SD Card	1	SD Card connector	TE 2041021-1
J2	IDC20	1	IDC 2x10 Header	BLK 10120560
Q1	BC337	1	NPN BJT Transistor	BC337
R10, R11	330Ω	2	standard 0.25W carbon film resistor	TRU TC-CFR0W4J0331
R1, R3, R5, R8	1200Ω	4	standard 0.25W carbon film resistor	TRU TC-CFR0W4J0122
R2, R4, R6	2200Ω	3	standard 0.25W carbon film resistor	TRU TC-CFR0W4J0222
R7, R9, R12, R13, R14	10kΩ	5	standard 0.25W carbon film resistor	TRU TC-CFR0W4J0103
U1	PIC16F1825	1	PIC 8-bit Microcontroller (DIP-14)	PIC16F1825-I/P
U2	74ACT08	1	Quad TTL 2-Input AND Gate	SN74ACT08N
U3	3.3V LDO	1	3.3V LDO voltage regulator	MCP1700-3302E/TO

Optional

Reference(s)	Value	Quantity	Notes	Part number
J1	-	1	1x2 header + jumper or wire	-
U1, U2	socket	2	DIP-14 socket	TRU 14-LC-TT
Case	ABS	1	Instrument Case, ABS 2.6x2.6"	HM 1593K(TBU|GY|BK)

Using sockets is recommended because it will allow you to reclaim the gates and microcontroler if your board is broken. This will also allow you to upgrade the firmware if a future firmware is released.

Bridging J3 connects the !ENBL pin on the microcontroller to the !ENBL pin on the 2x20 header, which is what you want for the overwhelming majority of cases where you're connecting the board to an external/secondary floppy drive port that has !ENBL2 in the connector where it should be. It's fine to bridge the two pins with a piece of wire, but if you want this expandability available to you, it'd be better to solder a two-pin header and stick a jumper on it when not in use. The pin closest to the center of the board is the one connected to the microcontroller.

BOM (adapter board)

This is a matching board for TashTwenty. Please use this one to avoid any damage to your computer or TashTwenty. Others adapters boards are wired differently

Reference(s)	Value	Quantity	Notes	Part number
J1	IDC20	1	IDC 2x10 Header	BLK 10120560
J2	DB19	1	DB19 wire male connector	Good luck.

BOM (external links)

Here is a mouser link (without the case):

• https://www.mouser.fr/ProjectManager/ProjectDetail.aspx?AccessID=f711e74993

IDC cable

You need a cable to connect both boards Any straight IDC-20 cable should work (pin 1 to pin 1, etc). Macintosh floppy cables are compatible. We used a Quadra 800 cable for prototyping (Apple P/N 590-0862-B).

PCBs

the PCBs are simple 2 layers boards. The gerbers are avaible in the release section. Check for the following files:

• TTT_10.zip: main board revision 1.0
• DB19_IDC20.zip: adapter board revision 1.0

You should be use any mainstream PCB manufacturer for theses. Nothing special about them. PCB thickness should FR-4 with a 1.6mm thickness On JLCPCB, select "Specify a location" to the option "Remove Order Number"

Building

Building is straightworfard. It's recommended to start with the SD Card connector, then components, and headers + sockets last.