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Another Lynx I needs repair


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#1 Nop90 OFFLINE  

Nop90

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Posted Sun Mar 3, 2019 3:34 PM

I was very lucky buying two months ago a not working Lynx II. It had only dirty contacts on all the 4 carts coming with it and a dpad stuck on right direction (still have to fix it, but sould be only a dirty contact).

 

Some days ago bought a Lynx I for 30 € and this time there is something broken (already tryed to short the battery minus with the audio jack mass).

 

Probing the circuit, the +5V point and the mass are in short circuit (measured it at the ends of D14). The zener diode and the mosfet, tested without desoldering them, seems ok.

 

Now I should start desoldering components in the hope that there is a fault component before mickey os suzie. Or I could connect the power supply and check if there is a transistor or IC heating.

 

But before doing anything I'd like to know if someone else experienced such an issue, what are the most common points of failure and how to check them.

 

 



#2 karri OFFLINE  

karri

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Posted Sun Mar 3, 2019 10:57 PM

I had a RAM chio that worked as a fuse. Replacing it fixed my Lynx.

#3 Stephen Moss OFFLINE  

Stephen Moss

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Posted Mon Mar 4, 2019 2:28 AM



Some days ago bought a Lynx I for 30 € and this time there is something broken (already tryed to short the battery minus with the audio jack mass).

Connecting what should and thus could be at 4V to 0V is not a good idea!

 

 

Probing the circuit, the +5V point and the mass are in short circuit (measured it at the ends of D14). The zener diode and the mosfet, tested without desoldering them, seems ok.

 

 

Not quite sure what you mean by "the mass".

When you say D14 is that D14 from the the schematic diagram on AA or have you transposed the component reference to that of the AA schematic because I am sure that schematic is for a Lynx 1, D14 on a Lynx 2 has nothing to do with the power stage at all. On the Lynx 2 D12 is the diode drawn immediately to the right of the MOSFET connected across the 5V power rails.  

 

There have been many posts here regarding Lynx's that do not turn on/off, I suggest using the search facility to find them as they will at least get you started.



#4 Nop90 OFFLINE  

Nop90

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Posted Mon Mar 4, 2019 4:32 AM

Not quite sure what you mean by "the mass".

Wrong translation from an ialin term Read "ground"

 

 

When you say D14 is that D14 from the the schematic diagram on AA or have you transposed the component reference to that of the AA schematic because I am sure that schematic is for a Lynx 1

 

I'm using the schematics on AA for the Lynx 1 (the one not working) where D14 is drawn just after the MOSFET and is good poiint for testing the voltage.

 

Anyway already found some broken components. First one is the L15 at the power supply input. The MOSFET too seems gone. I'll continue probing.



#5 Nop90 OFFLINE  

Nop90

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Posted Mon Mar 4, 2019 6:58 AM

After some small fixing I can power the circuit with 4 batteries.

 

Zener and MOSFET are gone. Bypassing the MOSFET the LCD backlight turns on, but there is no other sign of life.


Edited by Nop90, Mon Mar 4, 2019 7:14 AM.


#6 Nop90 OFFLINE  

Nop90

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Posted Mon Mar 4, 2019 7:48 AM

In the end found that powering the circuit the two ram modules became very hot.

 

Now I'll try replacing he MOSFET, the zener, the capacitors and the two ram modules.

 

This will take some time.






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