WP-34s USB PCB Board

[Sadsilence]

Hi,

I feel you ordered one or two DIY WP-34s USB Addon boards from me some time ago. An enlarged CAD print of assembled board and wire scheme should have been included. When not: shame on me.

Here they are together with short description.

1. Assemble and test WP34S USB Addon PCB
- Component names are printed on PCB, orientation of R1-R5 and C1-C4 does not matter, D1 and T1 SOT23-3 housing orientation is obvious
- Assemble R1, R2 27 Ohm
- Assemble R3, R4 3k3
- Assemble R5 390 Ohm
- Assemble C1, C2 47p
- Assemble C3, C4 100n
- Assemble D1 & T1
- Assemble FTDI-Chip IC1, take care that dot of housing is on same position as dot on PCB
- Assemble micro usb connector
(last two components require a little solder experience, a fine solder tip and a magnifier)

Connect PCB to a PC, check if RS232/COM port is seen by computer. No danger as PC switches off USB port in case of short curcuit. In case of unknown USB device or no reaction at all check solder points at R1, R2, USB micro connector solder points and FTDI-Chip solder points, rework and repeat.

2. Flash HP-20B/HP-30B

described @ free available WP34S manual Rev. 3.1. It is easier to do it with housing.

3. Open HP-30B housing

described @ free available WP34S manual Rev. 3.1. pages 190ff

Remove batteries first.

There are 5 screws with 2 screws hidden below bottom rubber line.

For separating front and bottom part of kernel housing with all the clips I would suggest a plastics "smartphone opener tool" often advertised for little budget. Using a screwdriver or swiss army knife will result in a lot of scratches on visible front side of calculator.

4. Remove LB1 & LB2 ferrits from calculator PCB

described with picture @free available WP34S manual Rev. 3.1 pages 190ff

5. Assemble crystal + crystal capacitors

see picture attached below (picture(s) are taken from WP34S manual Rev. 3.1 pages 190ff and slightly modified)

6. Cut away screw holder fixtures

described with picture @free available WP34S manual Rev. 3.1 pages 190ff

8. Do wiring between WP34S USB Addon and calculator PCB

I prefer doing that before I glue in PCB for obvious reasons. Wiring picture is attached (taken from WP34S Rev. 3.1 manual and slightly enhanced). I prefer enamelled wires but anything up to AWG28 is ok.

You can use two enamelled wires for connection of IR LED, too. That makes IR LED assembly more flexible and disassembly of housing easier. For test purpose I would not shorten IR LED pins at the moment. Just let IR LED "hang around" on wires which are connected to USB Addon board pads.

Do not forget wire between CR2032 battery holders. Without you will not get immediate impact, but only one battery is actually used and there will most probably a memory loss during battery exchange.

Now wiring can be tested by connecting USB board with micro USB cable to PC and playing around with WP34S features.

9. Glue in PCB

described with picture @free available WP34S manual Rev. 3.1 pages 190ff

10. Cut & drill outlets for USB connector and IR-LED in back part of calculator housing

described with picture @free available WP34S manual Rev. 3.1 pages 190ff

desolder IR LED from wires when using "wired IR LED solution", glue it in and shorten pins afterwards

11. Resolder wires to IR-LED pins when necessary and close housing

12. Assemble overlay when not done before.