Dead Turbo Grafx 16 Pad?

[backtoskooldaze]

Hi,Does anyone know how to fix a dead turbo grafx 16 pad?
There is no response from the pad what so ever? When i start a game and i have to press run to play the game nothing happens? There does not seem to be anything wrong with the cable or the wires inside the pad? The pad is like new hardly used?

[xolik]

This may seem like an obvious question, but have you tried using a different controller? I would be best to eliminate the acutal joypad input port as the culprit.

[rolins]

Most likely the rubber pads are either out of alignment or the contacts are dirty.

You should take the controller apart and clean the contacts and make sure the rubber pads are seated properly.

This usually solves my problem when my controllers fail to work.

[zborgerd]

The Turbo pads have a 74HC157 quad-2 input multiplexer IC in them.  If that fails, then the whole controller is bombed (unless you replace the chip).  If you're sure that the controller has a problem, and you are certain that it is not the cable, you may be able to test the chip with a multimeter and oscilliscope.  I've personally never seen one fail though, but I guess that this is the most likely place since it does all of the "work" in the controller.

http://www.gamesx.com/controldata/turbocont.htm
http://www.semiconductors.philips.com/acrobat/datasheets/74HC_HCT157_CNV_2.pdf

If you check the pins of U/D/L/R, and they are all "high" until a button is pressed (judging by this information), then you should check the outputs as well.  The multiplexer outputs are on pins 4/7/9/12.  You should see a logic change on these outputs if you press a button on the controller, but it might be hard to test (depending on how fast the Turbo polls the controller if you don't have the right tools).  Looks to me like it sets a line high to do one half of the buttons, and then sets it low to do the other half (on pin 1 on the IC).

The most simple thing, I guess, would be to make sure that a voltage (+5 v on pin 16) is there when the controller is plugged in.  Just be careful not to short your system.  Should be okay though, since all of the wires to the Turbo should be okay with 5V logic levels.

[backtoskooldaze]

Hi all thanks for your replies:) I have since bought another brandnew pad and it works a treat.I have opened the pad and reseated the rubber buttons etc...like the select+run but the pad has no response still? The little wires that go in to the pad look fine and the plug on the end looks fine? I have an electrical screw driver that has a red light inside and when touching something live and your thumb on the screw driver handle is lights red.So after touching the little round parts were the rubber button would press i get a red light on the screwdriver so that must mean there is life in the pad were the buttons are pressed? If i was to clean the circuit board parts were the buttons go what should i use?

[Keranu]

The Turbo pads have a 74HC157 quad-2 input multiplexer IC in them.

That's a mouthfull!

[zborgerd]

Hi all thanks for your replies:) I have since bought another brandnew pad and it works a treat.I have opened the pad and reseated the rubber buttons etc...like the select+run but the pad has no response still? The little wires that go in to the pad look fine and the plug on the end looks fine? I have an electrical screw driver that has a red light inside and when touching something live and your thumb on the screw driver handle is lights red.So after touching the little round parts were the rubber button would press i get a red light on the screwdriver so that must mean there is life in the pad were the buttons are pressed? If i was to clean the circuit board parts were the buttons go what should i use?

If you're cleaning some coated button contacts, you can simply do it with some rubbing alcohol and a cotton swap (Q-tip).

If the controller isn't very old though, then it's not likely the problem.

Sounds like you screwdriver has some sort of a logic probe or something.  The buttons will of course make it flash red, because I believe that they are always left "high"with a voltage (jusding by what the link says).  However, because of the way the multiplexer chip functions, even if the buttons have a voltage, it's still likely that the problem is the multiplexer IC.  I really don't know though because I've never opened one up.  I'm just basing my assumptions off of the limited info that I know about its design.

The odds of all buttons failing due to dirty contacts it pretty slim, unless you happened to dump a soda on the controller.