Lynx II Repair

[santac89]

Hello everyone! I just joined the forum since I'm trying to fix 2 Lynx II. I've read a lot of threads in the forum already trying to figure out what could be wrong with these 2 with no luck.

 

Both are C104471 Rev A versions. Both have been recapped and supplied with 5V through C41. One of them I'm pretty sure one of the ICs (or both) is dead since I attached a logic analyzer and also used a logic probe on the D* and A* pins and I see no activity (I only see a High on D0 on Hayato). Black screen, no sound and brightness wheel does nothing. So I kind of lost all hope with this one.

 

The other one shows activity on both Hayato, Suzy and DRAM which is hopeful but still I get this garbled screen (image attached). I've also tried using some headphone with a game inserted to check if its only a video problem but the only thing I get is a buzzing sound. I'm lost with this one since I checked almost everything I've found here in the forum. Does anyone has any idea of how I can continue? 

 

One idea I didn't try yet is to swap Suzy from the dead one (hoping that only Hayato is dead) to this one in hopes that maybe is malfunctioning.

 

Thanks in advance! And glad to be here!

 

 

[santac89]

So, I swapped SUZY and got a black screen, so it is definetly doing something plus I see actvity with the logic probe. Also put a new oscillator but got the same result as the picture. I'm totally lost here.

[santac89]

Also, I see in another thread (linked below) a similar behaviour with my LM386s. Pins GND and V+ have 0 volts. Could be this the cause or having those components broken should not interfere with video? Thanks!

 

Edited May 26, 2022 by santac89

[oski_98]

There's a lot of information on this forum about how to troubleshoot issues like that. You just have to go find it and be persistent.

[santac89]

Yes, I have been scouting the forum long before I created the post but still no luck. I wonder if SUZY is dead, I see with my probe that there is activity but all I get is that frozen "image" with no sound and as far as I know is rare that the IC would fail like that instead of just stop working. 

[santac89]

Leaving here the Voltage measurements for every TP to see if someone spots something.

 

- TP1 4,9v

- TP2 0v

- TP3 0v

- TP4 0v

- TP5 0v

- TP7 0v

- TP8 0v

- TP9 0v

- TP10 0v

- TP11 2,5v

- TP12 18,8v

- TP15 5v

- TP16 0v

- TP17 0v

- TP18 0v

- TP19 4,48v

- TP21 9,63v -> 18,2v (from min brightness to max)

- TP22 6,43v -> 13v (from min brightness to max)

- TP23 -3,8v -> -8,8v (from min brightness to max)

- TP24 1,3v -> 2,48v (from min brightness to max)

- TP25 2,05v -> 4,3v (from min brightness to max)

- TP26 2,5v

- TP28 0,022v