Lynx II D-Pad Issues?

[Phlibbit]

Hey everyone,

 

I just got my Lynx II back with a newly-installed McWill LCD and speaker, but upon playing the games, I noticed that something felt off with the D-pad.

 

So, I fired up the Lynx diagnostic program and did the button test, and--that confirmed it--yep, something's up with the D-pad.

 

The down and right directions are just fine, but left and up both register as left and up *combined*:

 

 

It was probably always like this since I picked this system up, but I didn't play with the system much before having the mod installed. Before I open up the case and start blindly messing with stuff, does anyone have any ideas? Much appreciated!

Edited April 26, 2018 by Phlibbit

[BadPricey]

Most probably the membrane is faulty. The bit between the front cover and pcb. I had a similar issue. Replacing it fixed it.

Hope this helps.

Rgds

BadPricey

[Phlibbit]

Most probably the membrane is faulty. The bit between the front cover and pcb. I had a similar issue. Replacing it fixed it.

Hope this helps.

Rgds

BadPricey

 

Do you know of a place that sells replacements?

[BadPricey]

 

Do you know of a place that sells replacements?

I got mine from a user on this site. Try pm'ing LX.NET, he helped me out. Other users have bought from Best Electronics I think.

Rgds

BadPricey

[moff000]

 

Do you know of a place that sells replacements?

 

 

Do you know of a place that sells replacements?

 

I got mine from here:-

https://www.ebay.co.uk/itm/10-Atari-Lynx-MK-2-hand-held-console-direction-button-rubber-pad-replacement-NEW/152657129174?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649

[Phlibbit]

Oh, fantastic! I just got a set of those. I'll try cleaning the contacts as well, but it'll be good to have some backup pads in case this issue comes back.

[BadPricey]

Oh, fantastic! I just got a set of those. I'll try cleaning the contacts as well, but it'll be good to have some backup pads in case this issue comes back.

It's the flexible membrane these things sit on that you need.

Edited April 26, 2018 by BadPricey

[+Stephen Moss]

Whoever fitted the new screen and speaker may have damaged the flex circuit as has already been suggested, however I can see how that would result in a button not operating as the flex circuit goes open circuit, but two buttons appearing to operate together would be an unlike result, that sounds more like a short circuit, particularly as Left and Up are side by side in the flex circuit.

 

Consequently I would think it more likely to be either...

a) If the d-pad and conductive contacts were removed during the LDC install it was not replaced correctly resulting in a Left or Up press causing both contacts to close at the same time.

b) The flex circuit was incorrectly inserted into the FCC connector causing a short between the Left and Up contacts which are side by side. Although an unlikely event try removing and re-inserting the flex circuit anyway.

c) A solder splash either on the FCC connector or flex circuit causing a short circuit between Left and Up - if you have access to a multi-meter remove the flex circuit from the FCC connector and measure the resistance between the 2nd & 3rd contacts both on the flex circuit and on the connector. If you do not have access to a multi-meter then try a visual inspection.

 

 

[Phlibbit]

Whoever fitted the new screen and speaker may have damaged the flex circuit as has already been suggested, however I can see how that would result in a button not operating as the flex circuit goes open circuit, but two buttons appearing to operate together would be an unlike result, that sounds more like a short circuit, particularly as Left and Up are side by side in the flex circuit.

 

Consequently I would think it more likely to be either...

a) If the d-pad and conductive contacts were removed during the LDC install it was not replaced correctly resulting in a Left or Up press causing both contacts to close at the same time.

b) The flex circuit was incorrectly inserted into the FCC connector causing a short between the Left and Up contacts which are side by side. Although an unlikely event try removing and re-inserting the flex circuit anyway.

c) A solder splash either on the FCC connector or flex circuit causing a short circuit between Left and Up - if you have access to a multi-meter remove the flex circuit from the FCC connector and measure the resistance between the 2nd & 3rd contacts both on the flex circuit and on the connector. If you do not have access to a multi-meter then try a visual inspection.

 

 

 

Is the "flex circuit" located underneath the D-Pad membrane? I've removed and reinstalled the FCC connector as well as the membrane and I'm getting the same results.

 

I did also notice that the screw that goes into the battery holder compartment was screwed in pretty tight, enough to warp the connector underneath. It didn't poke a hole through it, but it's pretty close. Could that be the cause?

[+karri]

You could have a look at the Lynx Wiki page https://console5.com/wiki/Atari_Lynx

 

There is good schematics.

You can see that the UP pin goes to TP3 and at the bottom of the flex connector the last pin goes to +5V.

The other joypad pins go to TP2 (DOWN), TP5 (LEFT), TP4 (RIGHT).

If you grab a multimeter and put one wire to +5V on the Lynx and another pin on th TP you should see how many ohms there is when you press a button. There is no need to apply power on the Lynx you can just measure the operation of the pins by measuring the resistance. You can also measure the resistance between the test points to see that they do not interfere with each other.

 

If this appears to be ok you can then power up the lynx and use a wire connected to +5V to poke the test points. When you put the +5 to UP you should receive an UP effect on the cart.

 

Edit: My guess is that the joypad shares the cart port. When Lynx reads something from the cart the 4.7k resistors let Suzy see the byte from the cart. When the Suzy does not read the cart it can see the buttons. The 4.7K resistors are weak enough not to interfere with reading the cart. I may be wrong here but this is my guess of how the Lynx works.

The signals on the Suzy are also named ROM0..ROM7 which kind of gives this away.

Edited April 29, 2018 by karri

[+Stephen Moss]

 

Is the "flex circuit" located underneath the D-Pad membrane? I've removed and reinstalled the FCC connector as well as the membrane and I'm getting the same results.

 

I think what you are referring to as the membrane and I am referring to as the Flex Circuit are the same thing, the thin plastic sheet with conductive tracks on it that plugs into the FCC connector.

[Phlibbit]

Thanks for the help, everyone!

 

I think I got this fixed--it was probably a combination of everything everyone has mentioned. The contacts on the flex circuit seemed just fine, so I kept the casing off and powered the Lynx on. It turned out that the membrane wasn't positioned *perfectly* so I was able to use the diagnostic program to adjust the membrane in real time until the D-Pad directions registered correctly.