Interesting Problem

[Sonoma76]

Hi gentle people:

I'm rebuilding an old system to control the X-10 modules scattered throughout the house. IT doesn't need to be much, so I blew the dust bunnies off of the following:

EFTX 5 Mobo (Don't ask, I don't know who made it, it's over 1 year old though. It has a 66mhz bus, SDRAM modules, and can support up to a 233mmx or K6 300)

Pentium 120
32mb EDO RAM
4mb graphx card
1.5gb IDE hard drive, 40x cdrom
AT Keyboard connection, serial mouse, one parallel port.

I've configured the jumpers to accept a p120, and hard drive and cdrom are set to master/slave respectively. When I boot up the system, the AMI bios works just fine. The ram counts up, the disks are recognized, and I proceed through the boot up.

HOwever, the moment I attach a keyboard, either a PS2 keyboard with an old AT adapter, or an old AT keyboard directly to the system, the speaker beeps in pulses as if someone is holding down a key for a long period of time. THe keyboard will not function, and I cannot get into BIOS to check things out. I've tried this with two different PS2 keyboards, two different PS2 to AT adapters, and finally an old AT keyboard. It starts beeping right when the ram test is going on, and if I remove the keyboard, it will stop beeping. I"ve swapped RAM and moved the video card around (not likely, I know, but you never know). I've tried it with a mouse plugged in and without a mouse (serial). Every jumper seems to be in the right place, according to the manual. And yes, this system has worked just fine before with a PS2 and AT keyboard. Still no dice. Any ideas learned fellows?

[Legoboy]

Either the keyboard encoder has died an awful death or there is a short (possibly between data and clk if the short was between +5v and Gnd then your keyboard will now be dead as well) on the AT socket on the board. If you have access to a multi-meter, you might try checking each AT input with all of the other inputs with the meter in continuity mode. Unfortunately, the path from the encoder to the rest of the board is a little too hard to test in this manner.

Good Luck!

Legoboy

[Sonoma76]

Legoboy,

Thanks for the input. I'm gonna try the multimeter tomorrow, see if your idea is correct.

Last week, I had this computer up and running on my keyboard, video, monitor switch. The KVM switch is designed for PS2 style keyboards and mice, both of which this computer doesn't have. So I simply used the ps2/at adapter and was able to type through the switch. Could this have shorted it out? Thanks.

[tlwhite76]

Sonoma76: Make sure the thin piece of metal between the motherboard and the case is extended where your mouse and keyboard are plugged in. I believe you are unknowingly grounding your motherboard. Extend the metal so it flexes. Your problem should then go away.