Lynx 1 (Model I) Right D Pad button pressing at random

[apr2499]

I have a Lynx model 1 that has started acting strangely. The right D-Pad button starts to press at random times. I even took off the D-pad magnets or contacts (whatever you call them) so that you just see the lynx i motherboard, and the right button still presses down. This is really easy to see in Klax as it will change difficulty from Easy to hard without me pressing anything.

 

I have not done the 5 Volt mod yet but the voltage to the screen is at 4.97 volts. None of the capacitors look swollen. Do you have any idea what this could be?

 

I just put in the McWill screen and really love this thing.

 

Any advice you can give would be greatly appreciated!

[7800fan]

https://atariage.com/Lynx/archives/schematics/Schematic_Lynx_UR_Low.html

 

Something is shorting out the line. Check the contact for anything on the controller panel. If it still acts up and you are sure it is not in the controller panel, then you may need to check the mainboard for loose metal bits or flaky component pulling the specific line high at random.

 

Worse case, you need a replacement Suzy chip.

[apr2499]

Thank you 7800fan for the reply. Call me a newbie, but I'm looking at that schematic and having trouble making heads or tails of it.

 

Where is the controller panel and what is a Suzy chip? I really not an idiot, just not familiar with the Lynx lingo yet!

[Trew]

I had this problem with my Lynx II just recently. I took it apart and gave the ribbon under and around the dpad a clean. The Lynx one doesn't appear to have the same ribbon... but did you give the dpad contacts etc a bit of a (gentle) rub? (Guessing you tried that though)

Edited May 12, 2016 by Trew

[apr2499]

I beginning to thing there is some sort of hardware failure. I have looked over this lynx motherboard many times and I don't see anything obvious. I even took the soldering iron and put it across the chips again just in case there are some old solder joint that were breaking a part.

 

The only thing i can think of would be to take a knife and cut the lead on board that goes to the chip and solder a wire there instead.

[apr2499]

I had this problem with my Lynx II just recently. I took it apart and gave the ribbon under and around the dpad a clean. The Lynx one doesn't appear to have the same ribbon... but did you give the dpad contacts etc a bit of a (gentle) rub? (Guessing you tried that though)

 

Trew, I tried cleaning all of the contacts. Unfortunately the dpad is build into the lynx mainboard. So I'm pretty much out of luck.

[Mojado]

 

Trew, I tried cleaning all of the contacts. Unfortunately the dpad is build into the lynx mainboard. So I'm pretty much out of luck.

Measure TP4 to see if it goes low when it presses at random. Also clean your cartridge slot. The right d pad signal can be shorting to ground there too. Inspect/clean your cartridge also.

Edited June 12, 2016 by Mojado

[+Stephen Moss]

Thank you 7800fan for the reply. Call me a newbie, but I'm looking at that schematic and having trouble making heads or tails of it.

 

Where is the controller panel and what is a Suzy chip? I really not an idiot, just not familiar with the Lynx lingo yet!

 

I have an electronic background and I think the Lynx schematic it is a hard to read mess so a non electrical person would have difficulty, Suzy is U2 as shown in the circuit linked to in the 1st reply.

If the problem was constant it would be easier to find, the problem with intermittent faults is that you can inadvertently reconnect bad joints as you make measurements meaning that you could be looking in the right place but not finding the right answer!

 

As Mojado said measure the voltage between U2 pin 1 or 2 (Gnd/0V) and TP4, if the voltage is fluctuating when the Lynx is seeing false right presses then the problem probably lies with the connectors, cables and their solder connections somewhere between TP4 up to and including the Right Switch.

 

If the voltage at TP4 is stable then the problem probably lies between TP4 and Pin 39 of U2 (Suzy), you could try following it through but it may be simpler to just try resoldering Pins 1 & 8 of RP2 and pin 39 of U2 first to see if that cures the problem.