Let’s build a brand new MSX computer – Part 2

PCB and components arrived. So many packages, from US, Spain, Czech Republic and China. I bought two sets of PCBs, and they are slightly different. Checking the components and comparing with the PCB footprints I figured out the DIN8 connectors will not fit and need to order new ones. The rest seems to be OK.

The only package that actually costed me a lot of taxes was the one sent by Mouser Electronics. That is because they only use Fedex to send their packages and there is no way around import taxes when using Fedex, the delivery guy comes with a portable credit card machine to charge you 110% of taxes before handle you the package.

<sarcasm>Thanks DRF, love you!</sarcasm>. Anyways, we can start building the MSX now.

I’ll start building the Keyboard, and in this post I’ll document every component I had to buy for the whole build. If you are interested in building a MSX computer or just need a reference for a specific component, you can use the lists I’m documenting here.

Building The Keyboard

For the keyboard I will start building the leveling elements, connecting them to the board and then soldering all resistors, diodes, capacitors, sockets, connectors, and key switches. Then we will fit the key caps appropriately.

First step is to setup the leveling kit that is used with the big keys on the keyboard as well as with the space key. First thing I need to say is that it is not a super easy thing. Those kits are formed by small plastic pieces that need to be mounted in a specific order and side, then the metal bars need to slide into those in the right way, so you get the expected leveling without breaking the plastic.

There is a way to connect the keys to the keyboard that you don’t need force anything. If you are forcing the connection, you are doing the wrong way and the plastic may break.

Keep in mind that you need to slide the small piece of plastic into the big one in a way that you keep the side with the two holes pointing to the place where you will hold the bar. The metal bar slides into the lowest hole.

A good video to understand how to build the stabilizer is available below. I just ignored the tip to cut parts of the pieces. My kit worked very well without any of those recommended changes.

When setting up the stabilizers into the board, connect the big part to the larger hole and gently push the other side of the plastic piece against the smaller hole. You will hear a click and the stabilizer will be mounted to the board.

After setting up the stabilizers and mount those into the board, we can move forward and start soldering the three through-hole 470 ohm resistors to the keyboard. Those are specific as R1, R2 and R3 and have no polarity.

The resistor array (RN1) is a 6 pin 4.7K ohm component that also goes into the board. Go ahead and solder it. As a tip use a piece of tape to hold it and turn the board, solder the first and the last pin, turn over remove the tape, make sure everything is aligned and then solder the rest of the pins.

There are three capacitors to be soldered. Two 0.1 uF, MLCC (C1 and C2) and one 10uF MLCC (C3). Those are not polarized and are located on the superior part of the board.

You will need to solder a 16dip300 socket and a 14dip300 socket to the board. They are also located on the superior part and will hold the logic chips used by the keyboard. The same strategy I explained for the resistor array can be used here. Just use a piece of tape to hold the sockets in place, turn the board and solder the first and the last pin.

Then remove the tape, adjust the socket to the right position (you may need to de-solder a pin) and solder the rest.

The picture below shows the keyboard so far.

Use the same strategy used for the sockets to solder the connector as well. It is a 2×8 pin header, right angle shrouded connector with 2.54mm pitch. It will be used to connect the keyboard to the mainboard using a flat table.

LEDs have polarity and need to be soldered in the right way. Usually, boards are marked with a squared sign where you need to solder the cathode (negative) but the thing is that some boards I soldered before were just the inverse. Apparently, there is no real standard and I usually use my multimeter to detect where is the cathode, putting a probe on the ground and checking the place where the led needs to be soldered. I could only do that to the LED indicated as D1 on the board.

I believe the other LEDs are only activated when you have power on the board and are used to indicate status of specific keys as they are located just under two of them. I’ll come back later and solder those when the boards are connected.

For the space key I bought a better switch from Mouser and that one was super easy to solder. It has small plastic connectors that fit perfectly to the board and leave just the connectors to solder. But the rest of the keys I purchased from AliExpress, and they don’t have those connectors.

They are just fixed by the contacts, and it is a problem to keep them aligned when soldering. The strategy I used was to go four by four using a tape to hold them in position, then turning the board and soldering just one pin. Then I used the solder iron and my hand to kind of align then before soldering the other pin.

It was just a lot of work to get everything aligned but the result was good.

I also didn’t like the fact that my AliExpress source provided different tons of brown for the switches. I believe they are all from the same quality (not super good), and after placing the keycaps nobody is going to notice, but it is annoying to see different tonalities when it is supposed to be just one.

Here is a picture of the almost finished keyboard and a time lapse of the whole process.

Bill of Materials (Reference)

To help others that may be interested on the project I’m pasting Sergey’s BoM here with the links I used to buy the components. Most of them are available from Mouser, UTSource and/or AliExpress. For the main board, I decided to use the Mouser automatic project cart shared by Sergey on his website here, but I’m also including links to the same components on AliExpress if you prefer to deal with them.

Keyboard components I purchased from AliExpress following the links I’m providing below.


TypeReferenceDescriptionQuantityPossible sources and notes
PCBOmega Keyboard PCB1You have multiple options here. (1) You can download the Gerber files from Sergey’s GitHub repo, create a zip and order minimum of 5 PCBs from PCBWay. (2) You can buy one of the spare boards from MSXMakers. (3) You can buy from eBay sellers, like those option 1/option 2.
Integrated CircuitU174LS145 Octal D-Type Latch1AliExpress
Mouser 595-SN74LS145N
Integrated CircuitU274LS07 Octal Bus Transceiver1AliExpress
Mouser 595-SN74LS07N
LED              D1      3 mm, green LED indicator1      AliExpress
Mouser 593-VAOL-3HDE4
LED              D2      3 mm, yellow LED indicator1      AliExpress
Mouser 593-VAOL-3HCE4
LED              D3      3 mm, red LED indicator1      AliExpress
Mouser 593-VAOL-3HAE4
Mouser 512-1N4148TR
Keyboard SwitchSW1-SW73MX Cherry – Linear73Make sure you purchase the 5 pin version as it is going to be easier to align the keys on the keyboard when soldering.

Mouser 540-MX1A-11NW
Switch Leveling KitSW13, SW49, SW64, SW65, SW73Leveling kit for MX 1×2, 1×2.25, 1×2.755AliExpress
Mouser 540-G99-0742
KeycapsSW1-SW73104 Keycaps kit for Cherry MX Keyboard1You have a lot of options here, here are a few alternatives on AliExpress:

Option 1
Option 2
ConnectorJ12×8 pin header, right angle, shrouded, 2.54 mm pitch1AliExpress
Mouser 710-61201621721 or use 2×8 pin female header to plug the keyboard directly to the mainboard using 15 mm standoffs between them: Mouser 200-ESQ10812LD
CapacitorC1, C20.1 uF, MLCC, 5 mm lead spacing2AliExpress
Mouser 594-K104K15X7RF53H5
CapacitorC310 uF, MLCC, 5 mm lead spacing1AliExpress
Mouser 810-FG28X5R1E106MR00
Resistor ArrayRN14.7 kohm, bussed, 6 pin SIP1AliExpress
Mouser 264-4.7K-RC
ResistorR1 – R3470 ohm, through hole3AliExpress
Mouser 291-470-RC

Main Board

TypeReferenceDescriptionQuantitySource and notes
PCBOmega Mainboard PCB1You have multiple options here. (1) You can download the Gerber files from Sergey’s GitHub repo, create a zip and order minimum of 5 PCBs from PCBWay. (2) You can buy one of the spare boards from MSXMakers. (3) You can buy from eBay sellers, like those option 1/option 2. Either way, pay attention to the footprints to make sure you are buying the correct connectors (specially the DIN8 used for RGB and Cassette ports)
Integrated CircuitU1Z80 CPU, CMOS, 40 pin DIP – Z84C00xxPEG1Take care here. I bought one Z80 from an eBay package that was supposed to have all Omega MSX “hard to find” components and it didn’t work. Then I bought two from UTSource that worked flawlessly. I would recommend UTSource to buy the Z80 (make sure you get the new ones, not used).
Mouser 692-Z84C0010PEG
Integrated CircuitU282C55 PPI, CMOS, 40 pin DIP – CP82C55AZ1eBay package, AliExpress
Mouser 968-CP82C55A-5Z
Integrated CircuitU3V9958 VDP, 64 pin DIP1I bought mine from an eBay package. But just figured out the seller is not including VDPs anymore. That is a hard one to buy cause there are lots of defective chips, used, in bad condition, etc. I recommend UTSource or trusted AliExpress sellers. Don’t choose the cheapest ones in AliExpress or you will have to return them.
Integrated CircuitU4YM2149 PSG, 40 pin DIP or AY-3-89101eBay package, AliExpress
Integrated CircuitU5RP5C01 RTC, 18 pin DIP1eBay package, AliExpress
Integrated CircuitU6512 KiB Flash ROM, 32 pin DIP – SST39SF0401AliExpress
Mouser 804-39SF0407CPHE
Integrated CircuitU7512 KiB SRAM, 32 pin DIP – AS6C40081AliExpress
Mouser 913-AS6C4008-55PCN
Integrated CircuitU8 – U11D41464, 64K x 4 DRAM, 18 pin DIP4eBay package, AliExpress
Integrated CircuitU12 – U14Simple Programmable Logic Device – ATF16V8B3AliExpress
Mouser 556-AF16V8B15PU
Integrated CircuitU15 – U184-by-4 Register File – 74HC670, 16 pin DIP4AliExpress
Mouser 595-CD74HC670E
Integrated CircuitU19 – U2174F541, 20 pin DIP3AliExpress
Mouser 595-SN74F541N
Integrated CircuitU2274HCT540, 20 pin DIP1AliExpress
Mouser 595-SN74HCT540N
Integrated CircuitU23, U2474HCT273, 20 pin DIP2AliExpress
Mouser 595-SN74HCT273N. Note U24 is optional – printer port support.
Integrated CircuitU25, U2674F245, 20 pin DIP2AliExpress
Mouser 595-SN74F245N
Integrated CircuitU2774HCT175, 16 pin DIP1AliExpress
Mouser 595-CD74HCT175E
Integrated CircuitU28, U2974HCT157, 16 pin DIP2AliExpress
Mouser 595-SN74HCT157N
Integrated CircuitU30, U3174HCT153, 16 pin DIP2AliExpress
Mouser 595-CD74HCT153E
Integrated CircuitU3274AHCT138, 16 pin DIP1AliExpress
Mouser 595-SN74AHCT138N
Integrated CircuitU3374AHCT125, 14 pin DIP1AliExpress
Mouser 595-SN74AHCT125N. Note U33 is optional – printer port support.
Integrated CircuitU34 – U36Dual Flip Flop – 74HCT74, 14 pin DIP3AliExpress
Mouser 595-SN74HCT74N
Integrated CircuitU37 – U3974AHCT32, 14 pin DIP3AliExpress
Mouser 595-SN74AHCT32N
Integrated CircuitU40, U4174HCT30, 14 pin DIP2AliExpress
Mouser 595-CD74HCT30E
Integrated CircuitU4274LS07, 14 pin DIP1AliExpress
Mouser 595-SN74LS07N
Integrated CircuitU4374HCT04, 14 pin DIP1AliExpress
Mouser 595-SN74HCT04N
Integrated CircuitU4474AHCT02, 14 pin DIP1AliExpress
Mouser 595-SN74AHCT02N
Integrated CircuitU4574HCT00, 14 pin DIP1AliExpress
Mouser 595-SN74HCT00N
Integrated CircuitU46Microprocessor Supervisory Circuit – ADM691A1AliExpress
Mouser 584-ADM691AANZ; Possible alternatives: MAX691, LTC691, ADM691
Integrated CircuitU47Sony CXA1645P RGB Encoder, 24 pin DIP-4001eBay package, AliExpress
Integrated CircuitU48MCP6281-E/P Operational Amplifier, 8 pin DIP1AliExpress
Mouser 579-MCP6281-E-P
Integrated CircuitU49LM311N, Voltage Comparator, 8 pin DIP1AliExpress
Mouser 926-LM311N-NOPB. Note U49 is optional – cassette recorder support.
CapacitorC1 – C580.1 uF, MLCC, 5 mm Pitch58AliExpress
Mouser 594-K104K15X7RF53H5
CapacitorC59 – C64220 uF, Electrolytic6AliExpress
Mouser 647-UBW1E221MPD. Note C62 – C64 optional – RGB output support
CapacitorC65 – C67100 uF, 16V, Aluminum Organic Polymer3Part of the kit bought previously (AliExpress)
Mouser 80-A750EK107M1CAAE18
CapacitorC68 – C7010 uF, MLCC, 5 mm Pitch3AliExpress
Mouser 810-FG28X5R1E106MR00. Note C71 optional – cassette recorder support.
CapacitorC71 – C7710 uF, Electrolytic7Part of the kit bought previously (AliExpress)
Mouser 647-UPW1E100MDD1TD. Note C71 optional – cassette recorder support.
CapacitorC781 uF, Electrolytic1Part of the kit bought previously (AliExpress)
Mouser 710-860020672005. Note C78 optional – cassette recorder support.
CapacitorC79, C8022 nF, MLCC, 5 mm Pitch2AliExpress
Mouser 810-FG28X7R1H223KNT0. Note C79, C80 optional – cassette recorder support.
CapacitorC811.5 nF, MLCC, 5 mm Pitch1AliExpress
Mouser 810-FG28C0G1H152JNT0
CapacitorC82 – C84330 pF, MLCC, 5 mm Pitch3AliExpress
Mouser 810-FG28C0G1H331JNT0
CapacitorC8547 pF, MLCC, 5 mm Pitch1AliExpress
Mouser 810-FG28C0G1H470JNT0
CapacitorC86, C8733 pF, MLCC, 5 mm Pitch2AliExpress
Mouser 810-FG28C0G1H330JNT0
CapacitorC88 – C9030 pF, Trim Capactiors, 5 mm Pitch3AliExpress
Mouser 659-GKG30015. Note: Can be replaced with Mouser 810-FG28C0G2A270JNT0 if color subcarrier frequency tunning is not required.
CapacitorC9127 pF, MLCC, 5 mm Pitch1AliExpress
Mouser 810-FG28C0G2A270JNT0. Note C91 should be 18 pF for PAL support.
CapacitorC92, C9322 pF, MLCC, 5 mm Pitch2AliExpress
Mouser 810-FG28C0G1H220JNT0
CapacitorC944.7 pF, MLCC, 5 mm Pitch1AliExpress
Mouser 810-FG28C0G1H4R7CNT0
Resistor ArrayRR1 – RR410 kohm, bussed, 10 pin SIP4AliExpress
Mouser 652-4610X-1LF-10K or Mouser 652-4610X-AP1-103LF
Resistor ArrayRR5 – RR74.7 kohm, bussed, 10 pin SIP3AliExpress
Mouser 652-4610X-1LF-4.7K or Mouser 652-4610X-AP1-472LF
Resistor ArrayRR8, RR104.7 kohm, bussed, 6 pin SIP1 (2)AliExpress
Mouser 652-4606X-1LF-4.7K or Mouser 652-4606X-AP1-472LF. Note RR10 is optional – Memory pager size workaround.
Resistor ArrayRR9470 ohm, bussed, 6 pin SIP1AliExpress
Mouser 652-4606X-1LF-470 or Mouser 652-4606X-AP1-471LF
ResistorR11 Mohm, axial1AliExpress
Mouser 603-MFR-25FBF52-1M. Note R1 is optional – PAL support.
ResistorR2, R3470 kohm, axial2AliExpress
Mouser 603-MFR-25FBF52-470K
ResistorR4220 kohm, axial1AliExpress
Mouser 603-MFR-25FBF52-220K
ResistorR5, R6100 kohm, axial2AliExpress
Mouser 603-MFR-25FBF52-100K
ResistorR7, R847 kohm, axial2AliExpress
Mouser 603-MFR-25FBF52-47K
ResistorR9, R1020 kohm, 1% tolerance, axial2AliExpress
Mouser 603-MFR-25FBF52-20K. Note R9 should be 16 kohm, 1% for PAL support.
ResistorR11 – R1410 kohm, axial4AliExpress
Mouser 603-MFR-25FBF52-10K. Note R11, R12 are optional – cassette recorder support. Note R14 is optional – RGB output support.
ResistorR155.6 kohm, axial1AliExpress
Mouser 603-MFR-25FBF52-5K6
ResistorR16 – R224.7 kohm, axial7AliExpress
Mouser 603-MFR-25FBF52-4K7. Note R18 – R20 are optional – cassette recorder support.
ResistorR23, R242.7 kohm, axial2AliExpress
Mouser 603-MFR-25FBF52-2K7. Note R23, R24 are optional – cassette recorder support.
ResistorR25, R262.2 kohm, axial2AliExpress
Mouser 603-MFR-25FBF52-2K2
ResistorR27 – R331 kohm, axial7AliExpress
Mouser 603-MFR-25FBF52-1K. Note R31, R32 are optional – cassette recorder support. Note R33 is optional – RGB output support.
ResistorR34470 ohm, axial1AliExpress
Mouser 603-MFR-25FBF52-470R
ResistorR35180 ohm, axial1AliExpress
Mouser 603-MFR-25FBF52-180R. Note R35 is optional – RGB output support.
ResistorR36120 ohm, axial1AliExpress
Mouser 603-MFR-25FBF52-120R. Note R36 is optional – RGB output support.
ResistorR37 – R42100 ohm, axial6AliExpress
Mouser 603-MFR-25FBF52-100R. Note R42 is optional – cassette recorder support.
ResistorR43 – R4875 ohm, axial6AliExpress
Mouser 603-MFR-25FBF52-75R. Note R46 – R48 are optional – RGB output support.
RelayRY15V SPDT relay1AliExpress
Mouser 653-G5V-1-DC5 or Mouser 653-G5V-1-T90-DC5
InductorL168 uH, axial1AliExpress
Mouser 542-78F680-RC
InductorL2, L35.6 uH, axial2AliExpress
Mouser 542-78F5R6J-RC
Mouser 512-1N4148TR. Note D1 is optional – cassette recorder support.
TransistorQ1, Q2PN2907A2AliExpress
Mouser 512-PN2907ATF. Note Q1 is optional – cassette recorder support; Q2 is required for V9938 VDP only
CrystalY121.477270 MHz1AliExpress
Mouser 695-HC49US-214-U
CrystalY232768 Hz1AliExpress
Mouser 815-AB38T-32.768KHZ
CrystalY34.433618 MHz1AliExpress
Mouser 520-HCU443-20X. Note Y3 is optional – PAL support.
PolyfuseF1750 mA, radial, 5 mm pitch1AliExpress
Mouser 650-RUSBF075-2
ConnectorJ1DC Power Jack, 2mm1AliExpress
Mouser 806-KLDX-0202-A
ConnectorJ2RCA Phono connector, Yellow1AliExpress
Mouser 490-RCJ-014
ConnectorJ2RCA Phono connector, White1AliExpress
Mouser 490-RCJ-013
ConnectorJ4Mini DIN 4-pos, Right Angle, PCB mount1AliExpress
Mouser 490-MD-40SM
ConnectorJ5, J6DIN 8-pos, Right Angle, PCB mount2This is a problematic connector. Depending on which PCB you get, you may need to purchase connectors from Mouser or AliExpress. Check the PCB before you buy it.

Mouser 490-SDF-80J. Note J5 is optional – RGB support; J6 is optional – cassette recorder support.
ConnectorJ7, J8Sub-D DE9M, Right Angle, PCB mount2AliExpress
Mouser 523-L717SDE09P1ACH3R
ConnectorJ9Micro Ribbon 14-pos, Female, Right Angle, PCB mount1AliExpress
Mouser 636-112-014-213R001. Note J9 is optional – printer port support.
ConnectorJ108 pin friction lock connector1
Mouser 571-6404568
ConnectorJ112×8 pin header, shrouded1AliExpress
Mouser 710-61201621621
ConnectorJ122×20 pin socket1AliExpress
Mouser 517-929852-01-20-RB
ConnectorJ132×2 pin header1AliExpress
Note: Optional /RESET and /NMI header
ConnectorJ141×13 pin header1AliExpress
Note: Optional Color Bus header
ConnectorSLOT1, SLOT250 pin card edge connector2AliExpress
Mouser 571-5530843-5
Battery HolderBT1CR2032 Battery holder1AliExpress
Mouser 122-2420-GR
BatteryBT1CR2032 Battery1You can purchase from your local convenience store.
IC SocketU1, U2, U440 pin DIP3AliExpress
Mouser 517-4840-6000-CP
IC SocketU364 pin DIP1AliExpress
IC SocketU6, U732 pin DIP2AliExpress
Mouser 517-4832-6000-CP
IC SocketU4724 pin DIP, 400 mil spacing1Mouser 517-4824-6000-CP or 517-4824-3000-CP. Note: Cut the socket in the middle. If using a socket with 600 mil spacing, remove excess material. Alternatively, solder U47 (CXA1645P) without using a socket.
IC SocketU12 – U14, U19 – U2620 pin DIP11AliExpress
Mouser 517-4820-3000-CP
IC SocketU5, U8 – U1118 pin DIP5AliExpress
Mouser 517-4818-3000-CP
IC SocketU15 – U18, U27 – U32, U4616 pin DIP11AliExpress
Mouser 517-4816-3000-CP
IC SocketU33 – U4514 pin DIP13AliExpress
Mouser 517-4814-3000-CP
IC SocketU48, U498 pin DIP2AliExpress
Mouser 517-4808-3000-CP

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