FS-A1FX/WX/WSX memory area PCB repair

Champion (325)

09-03-2005, 21:22

Wow, this will be a tough one!!!

Got today some parts from an old FX with a WSX case. The motherboard has almost no traces on the user RAM area, since someone tried to upgrade from 64 to 256K and pulled almost all the PCB traces. Of course, the machine doesn't work anymore

My first thought: Redo the entire memore section in a separate board, and try to solder it on the puter. Of course this is not the prefered solution, but a "more-or-less" one.

So I need the following help:
- Can someone take a good high-resolution picture of the BOTTOM of the user memory area of a FX, WX or WSX motherboard?
- Can someone tell me which signals from the T9769A are used on the memories (I can guess that, but is safer to ask)
- Anyone has schematics or a service manual from the FX/WX/WSX panasonic computer?
- any advice you think I should have?

Also, to "complete" my puter, I need the following items:

- Power transformer (any voltage input) and/or info of what voltages does it outputs, so I can test here with another transformer
- Two small knobs from the front panel (ren-sha-turbo speed control and the other besides it)
- Small key left of space bar, or better, entire keyboard assembly
- 720K floppy drive (I wouldn't like to use an external drive).

Anyone can help?

Thanks a lot,
Alexandre Souza
Brazil

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By dhau

Paragon (1570)

09-03-2005, 21:36

I'll provide shots of WSX board and help you out with signal locations. From your request is does sound like it is better to re-house your motherboard (after repair that is) in a baby-AT case. I used hot glue to repair WSX keyboard, brutalized in transportation (very bad packaging).

By Alexandre_Taito

Champion (325)

09-03-2005, 21:46

Thanks a lot dhau! I have the entire case of the WSX and love that, The keyboard SEEMS to be working, missing only the key top between the space bar and GRAPH key, but I can only test with a working motherboard. This is one of the most confortable keyboards I've ever seen!!! I can live with an external floppie (and the circuit to use common PC floppies), but would love to have the entire FX/WSX working again. This is one of the most beautiful computers I've ever seen!!!!

BTW, if you could measure the output voltages of the power transformer, would also be great. Looking at the connector, seems that it is:

1 - AC
2 - GND
3 - AC
4 - AC

Looking at the board, it seems that:

1 - 8VAC
2 - GND
3 - 8VAC
4 - 15VAC

because 1 and 3 pass thru diodes and join toghether. 4 goes to two diodes, one feeding a 78L12 and another (reversed) feeding a 79L12. Seems easy to spot, but would be good to have some advice on that. The safe man died old enough

Greetings!

By [D-Tail]

Ascended (8263)

09-03-2005, 23:58

The key between Graph and Space, and the key between Space and Kana, are the Japanese Yes/No keys. They don't particularly mean anything and cannot be read (normally) as input keys. They're only used by the internal software

So your keyboard is perfect, that's always nice to hear

By Alexandre_Taito

Champion (325)

10-03-2005, 00:14

GOOD NEWS!!!

Solved the memory problem. I'll put a step-by-step tutorial in www.tabajara-labs.com.br/msx2plus still this night. Some tips for someone having a problem like this:

- Take magic tape and isolate with plastic or paper the area you are working, because the rest WILL be a mess
- Use steel wool to clean the topmost layer of paint of the PCB, so you can see the traces of the board going back and forth
- study how the ICs are connected, it can help a lot.
- clean everything and use very thin wire to connect the pads and the traces
- If there are empty IC spaces, populate it with sockets - it helps you to hang the wires to solder
- See how I did, and you will understand :)

Now, my problems are almost over. I still need to:
- discover the right voltages of the AC Transformer
- Find the rensha-turbo and the button at its right
- it would be great if I could find the yes key to make the keyboard complete
- test the keyboard with the lid closed and everything working
- install the "second source" FM chip (U3567A) with the adapter board
- Understand what all that rom space is for (any expanded slots inside avaiable for expansion?????) and make some use of that
- understand HOW the floppy drive is fixed inside it (I'll try to adapt a PC drive using a circuit I have here)
- Put everything back on the case, close it, and be happy with my dream puter :)

Thanks you all
Alexandre
(PS: I know, my english is sucking today, I'm waaaaayyyyy tired)

By Alexandre_Taito

Champion (325)

10-03-2005, 01:16

Update:
Running with a 24 + 24 transformer on place of the original (still without floppy)

Pinout: transformer gives me 24 - gnd - 24
So it is
1 - 24V (tap 1)
2 - GND
3 - 24V (tap 2)
4 - 24V (from tap 1 or 2)
Still working half an hour, maybe I'll put a small heatsink on the main switching transistor

EEEHHH, my WSX!!!

By Alexandre_Taito

Champion (325)

10-03-2005, 04:48

Another update:
Everything running fine Just need to find the internal bracket for the drive (I'll put a PC drive converted to 720K), to know the voltages of the power transformer and some cosmetic thingies.

But one question: My motherboard is the FX one. There is ONE rom on the board. Can I get rid of that inicial menu? Can I burn EPROMs and put it there? Do I have /sltselx lines for expanded slots inside the FX? How that EPROMs works? A special kind of mapper or simple expanded slot?

Thanks!

By dhau

Paragon (1570)

10-03-2005, 15:43

Initial menu can be switched by external switch. If it's off - you get menu, if it's on - you get MSX BASIC

By dhau

Paragon (1570)

10-03-2005, 22:03

Do you still need the shots of the board?

By Alexandre_Taito

Champion (325)

11-03-2005, 00:38

No dhau, thanks a lot! But would apreciate if you could do a simple voltage measurement on the transformer connector on the motherboard...

By Alexandre_Taito

Champion (325)

11-03-2005, 04:23

Just to keep you informed:
Installed the (at this moment external) PC-Modified floppy disk. I used Hans' pinout conversion for the turbo-r computer, and everything is working fine! Thanks Hans!

Still to do:
- Install the U3567A clone FM chip (since the YM2413 is impossible to be found here and I have some U3567A)
- Find someone with a spare FDD internal support (buááá, I don't want my floppy to be external!!!)
- Fit the CORRECT transformer in place. I'm still using the 24+24V, but it is too much voltage, the internal power supply (specially the main switching transistor) is getting too hot. What a service manual would help here....
- Close the lid and hope to never open it anymore

Greetz from Brazil!