Throttle Keyboard Membranes.

The throttle's keypad rubber membranes are similar to what's inside for remote controls we use for so many things these days, including our TVs etc.

Under the button is a "dome" with a carbon impregnated "cap". When the button is pressed down, these caps contact the circuit board and complete a circuit via a matrix to tell the microcontroller that a button has been pressed.

These "domes" can be a source of intermittent keyboard operation with an accumulation of moisture from our hands and dirt/dust can cause intermittent operation of the keypad. If the throttle works normally when plugged in, then there is no problem with the membrane and circuit board.

I have "fixed" a few TV remotes by cleaning the black residue that accumulates on the circuit board. This residue comprises of carbon and moisture that builds up in the remote while we are holding the remote. If my kids are any indication, they hold the remote while "surfing" the channels during add breaks etc, for hours. Seems they have to watch 10 channels at once.

In the end they fail, as this carbon is necessary to provide the circuit for the microcontroller that the button has been pressed. Cleaning this residue away, that by now has become an "insulator" over the circuit board tracks, does restore operation for a while. The loss of this carbon is the problem that eventually will cause total failure, but the TV might die or is replaced in the meantime, so this interim "fix" is seen as a permanent repair. The rubber "dome" without carbon is an "insulator".

The NCE Procabs and Cab04/5s have a similar arrangement, as shown left.

I figured I needed to “add” some carbon to the dome caps to improve the “circuit”.

Kadee “Greas-em” (Kadee No.231) that many of us already have for maintenance of our couplers, came to mind, to try as a fix.

Using a Cotton Bud, I applied some some “Greas-em” powder to my well used “original” Procab, but obviously too much. After pressing the button, the display locked on to this selection. The “Greas-em” powder left on the circuit board after contact, was enough to keep telling the "electronics" that I was still pressing the button. Obviously too much powder, I wiped the domes clean and tried it again. Eureka – it worked.

Try using some Greas-em but if you cannot get it to work correctly, NCE sells the membrane as a spare part. Some of the real early throttles like the System One units, there are no spare parts, so persevere with the “Greas-em” to get them to work.

Good Luck.