Fault Casio PV-7 keyboard

By jltursan

Prophet (2619)

jltursan's picture

11-06-2009, 15:02

I'm trying to diagnose a faulty PV-7 and I'm a bit stuck.

After replacing some VRAM ICs only a problem remains in the machine, the keyboard doesn't work at all. At first and after replacing its keyboard with 2 other (untested) ones (one from a PV-16 and another from a PV-7) I wasn't able to see any progress, no working keyboard.

I quickly started to think that the I/O controller was faulty (I forgot to mention that joysticks doesn't work neither); but the mainboard, although simple, was strange to me and I wasn't able to find the IC in charge of I/O; there's only a SMD IC named MB64H131 that looks suspicious to me, maybe it's the I/O controller; but I haven't found any info related.

As a last resort, I tried a PC keyboard adapter that plugs into the cart slot an bingo!, the keyboard works fine; so, anyone knows if the slot data lines are routed through the controller IC?, I guess so; but I'm a total noob on electronics theory.

Could it be that all the 3 keyboard membranes are faulty?

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By Manuel

Ascended (18855)

Manuel's picture

11-06-2009, 18:43

Doesn't the joystickwork via the PSG and the keyboard via the PPI?

By Sonic_aka_T

Enlighted (4130)

Sonic_aka_T's picture

11-06-2009, 19:48

The PC keyboard adapter doesn't route through the controller IC. I doubt all 3 membranes are faulty, you'd expect at least some keys to work on one of 'em. Most likely the PPI is faulty. It's quite possible this affects the PSG as well, as they're linked iirc.

By jltursan

Prophet (2619)

jltursan's picture

12-06-2009, 00:05

Well, it's fully working now! Big smile


1) Joysticks work fine. Seems that the cartridge selected to make the tests doesn't have a game start implemented by pressing fire...Eek!

2) I was able to found some working keys on 1 keyboard; so I started to check the membrane and found that the connector end was pretty dirty, also seems that the tracks conductive substance vanish easily. Once cleaned, all keys worked fine; even the integrated joystick works very softly Smile

Another Casio PV-7 that comes again to the arena! Running Naked in a Field of Flowers

Btw, the PSG has two bits that control the direction of the joysticks ports (input/output); but I suposse the data is readed by means of the PPI.

Thanks for the hints!