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captianpattson

Lynx voltage test locations

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Hey guys, I got a really nice Lynx 2 that doesn't power on. I replaced the caps with no change. I've read through dozens of threads and I'm not sure which pins on which ICs I need to test to see if I haven't over voltaged the thing. I've read a bunch of threads where people tried the headphone jack-jumper-trick and toasted their stuff. I'd like to go about troubleshooting this the proper way but I haven't found any pics pointing out where to measure from. I know questions like this have been asked over and over, so I appreciate everyone's patience. Thanks!

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It is difficult to produce a single image of the PCB showing where exactly to measure, one image would be required per measurement and take a longtime to produce which is probably why there are none.

The attached image should contain all the components for the power circuits. Find U6 (lower half, just left of centre), pin 1 is on its Top Left corner and as with all DIL IC's pin count increases in an anti clockwise direction so...

Pin 7 (GND) is bottom left corner,

Pin 8, bottom right corner and 

Pin 14 (Vcc), top right corner.

 

For everything else if you are not sure which pin or end of a component is which take a close look at the PCB traces, follow them round and see what else they connect to, if it matches with a connection drawn on the schematic then you are probably looking at the right place.

 

For those components draw on the schematic to the left of the MOSFET (Q12), use Pin 7 of IC6, the applicable connection of the battery connector or TP16 as the GND for your meter when measuring voltages (supply voltage measure 9V when on/using batteries or maybe a bit more when off using a power unit).

For those components drawn on the schematic to the right of Q12 you can use the A (left of the three) pin of Q12, either pin of L15 or the left end of D13 as the GND for your meter when measuring voltage.

 

 

Note:

If you have the COM lead of your meter connected to the GND point for components draw left of the MOSFET but are measuring a voltage on a component drawn right of the MOSFET you will measure 9V not 5V. *** THAT IS CORRECT ***. In normal working operation 4V is dropped across Q12. and consequently you will only read 5V on the 5V parts of the circuit when the COM lead for the meter is placed on one of the indicated GND points for components that are draw to the right of Q12.

The exception to this is the parts of U6 drawn to the right of Q12, when the Lynx is off you should measure 9V or 0V (COM lead on U6, pin 7), when the Lynx is on and working correctly those gates in conjunction with Q8, R72 & C43 form an oscillator. Consequently, an exact voltage for comparison is difficult to get it is dependant on several factors, that said when the Lynx should be on (Pin 10 of U6 approximately 0V) the voltage will not be constant at any of the possible the supply voltages (0, 9 or 5), if it is you have a problem (possibly blown Q8).      

Atari-Lynx-II Power Componets.jpg

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