Sega CDX woes, CD player works but not games?

I'd say he meant the transistor that definitely has solder between two pins:



You CAN adjust a laser with trial and error, but you SHOULDN'T. The correct way is with an oscilloscope and the correct test CD.

 

They said pin 3, so I think they meant the MCU. The transistor is not shorted either, its designed that way. In fact, I dont think those are transistors. Its very odd, they are all over the board but they do not check out as transistors with a meter. I'm very curious to know what they may be- I get nothing with a diode check and resistance check just gives an open circuit.

As for laser adjustments...*shrug* I've had some success with it over the years. The pots on the CDX are much easier to safely adjust than the laser itself and I fixed a couple units adjusting them without a scope. Ideally, a scope is the way to go of course.

-Segasonicfan

 

They can be diodes. If the pins are shorted that way in the board layout, the part then is definitely a diode.

 

Thanks for this great reply. Got a little burned out and busy with other stuff but I'm taking a stab again at fixing this (fixed another CDX too in the meantime, woot).

Thing is, the CDX doesn't have a LC8951x chip, it has this: http://console5.com/wiki/LC78681E
I see LRCLK on there but that's all right now...do you know what the equivalents would be for SDATA and BCLK? looks like the MCD2 equivalent CXA1082 and CXD1161 have been combined in the LC78681E (I guess its a servo driver and CD DSP in one). Then this talks to the LC78681E. I just don't know how, exactly.

EDIT: looked at the LC78681 datasheet and I guess the D/A outputs are DACLK, DFOUT, LRCLK, and WLCK. So I should check these, yeah?

I'll have to figure out with traces talk to the Sega ASIC...a little tricky for I can trace from the ASIC itself I guess through the board connections

Also, I traced P32 and it does indeed connect with pic 87 on the 315-5632.

Thanks for your help!

-Segasonicfan

 

ah, actually nevermind. this repair is just wayyyy too hard. gonna keep this unit around for spare parts.

-Segasonicfan

 

Hi mates,

I take this thread to ask if anybody knows where to buy the right lens for a CDX, because I've tried several without suscess. I also do the same question here

http://www.neo-geo.com/forums/showthread.php?256815-Sega-CDX-dim-RGB-Issue&p=3855825#post3855825

help much appreciated.

Un saludo

 

Please don't divert the thread here. Just start your own or ask on sega-16 forums. That's a common issue.

 

Hi mate,

I'm sorry to post in the wrong place, I'll open a new thread on the sega-16 forums.

Un saludo

 

Got it Working!
so this long story finally has a happy ending. Thank you eke, Oliveira, and Retro! I thought this one was really toast but after countless hours troubleshooting I discovered the 74HC245 was the culprit. It was fried internally and thus kept the MCU and other stuff from switching the data mode (I presume). Swapped in a new one tonight (a 74LS245 from a broken Saturn, heh) and it boots and runs games like a charm!
...rise from your grave!

 

Wow! Breezed through/reviewed your thread after you posted this update. Congrats on your fix. These are typically the fixes where I stand up, point to the device, and yell "BOOOM!" when I see it working.