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Help in diagnosing issue in Lynx 2


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#1 hexcor OFFLINE  

hexcor

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Posted Sun Jan 13, 2019 7:31 PM

Recently got a Lynx 2.  When powered on, the screen was white and there was no sound.  I ended up ordering a cap kit and the Voltage Regulator Rebuild from Console 5.  Everything went fine, but when powering on, the screen turns on for a second and off.  The power light turns on for MAYBE 0.5 seconds, then just flashes.

 

I looked over my work and everything looked ok. One weird thing, C11 shows continuity at both vias... this... this is odd, no? I have a working Lynx 2, but I have not had the time to open it up and check this.

 

Any ideas?



#2 Stephen Moss OFFLINE  

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Posted Mon Jan 14, 2019 3:16 AM

As I recall a flashing power led means low voltage which probably explains why the Lynx turns off. I suggest rechecking your work for errors, particularly inserting D13 in the wrong way around.



#3 hexcor OFFLINE  

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Posted Mon Jan 14, 2019 6:13 AM

I will check that tonight, as I remember, the stripe (per console 5) should be facing to R74,which I THOUGHT I double checked.

 

Should I not be concerned with the continuity between the vias for a capacitor?  Wouldn't that mean power would be bypassing the capacitor?  I used 91% IPA (although it's old) wonder if I did a poor job cleaning the flux there too.

 

 

I will also take apart my other Lynx 2 that works and check there.  There does seem to be a bunch of vias for caps that are going to the grounds, I don't know if thats correct either, again, i'll check that too



#4 Stephen Moss OFFLINE  

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Posted Tue Jan 15, 2019 2:22 AM

My D13 has 3 stripes Green, White & Gold, the gold is nearest to R74, if your diode has only one black stripe then that should be nearest R74.

 

I cannot locate C11 so am not certain where you are measuring, particularly in reference to the via's, I would try measuring across C11 directly in case you are measuring across the wrong places & if it still looks wrong compare it with your working Lynx to be certain if that is a correct or incorrect reading.

Note: You will usually read something across an electrolytic capacitor, usually a varying value as the power used for the continuity measurement charges the capacitor so it may well be that you are seeing, if it is a fixed value regardless of whatever way round you place your meter probes that could indicate an issue but there may just be something with a low ohmic value in parallel somewhere hence checking against the other Lynx  


Edited by Stephen Moss, Tue Jan 15, 2019 2:37 AM.


#5 hexcor OFFLINE  

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Posted Tue Jan 15, 2019 6:06 AM

I am using the map from console 5 ( I removed all the caps, D13 and the mosfet and checked some of the vias the caps would be in and still have a short to ground

 

my guess here is that a chip must have fried, which is causing the error.  I'm glad I only paid $30 for the lynx and whatever console 5 charges for the caps/regulator kit.. 



#6 -^CrožBow^- OFFLINE  

-^CrožBow^-

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Posted Tue Jan 15, 2019 4:27 PM

Some of the caps are tied to ground for their negative polarity. So that isn't unusual. My guess is perhaps the mosfet isn't quite in place properly?



#7 karri ONLINE  

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Posted Tue Jan 15, 2019 9:15 PM

If I remember correctly there is zero ohm resistors that separate areas on the pcb. You could remove them to pinpoint the area that is shorted. Another choice is to feed 5V from a regulated supply and see which part heats up. I located broken RAM chips that acted as a fuse this way on a Lynx I




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