Hey guys, I have a Sega CDX I am trying to fix for a friend. The CDX is in great condition and even has the actual Sega power cord with it. The problem I'm having is the system does not turn on. When the power button is pressed the LCD does not light up, but the disc will spin a tiny amount. I checked the fuse using a multimeter and it seems fine, power goes through it. After looking around I wired the 5v source from the power board to the 3rd pin on the AV port and the system turns on when plugged in. In this state the system works, but the front switch does nothing. It seems like the 5v source is shorting somewhere on the board I'm just not sure where. I have tried replacing some of the basic capacitors on the top side of the board just to rule those out. Any advice is appreciated, thanks!
Walkman mode seems to work, i also noticed that when plugged in with the adapter and i press the play button track number 1 comes up on the LCD. Still no orange back light however.
I have one which has similar problems. I think it's the 5660 chip which is dead as it doesn't heat up or the z80 ram chip which has bad scope outputs. I haven't got round to swopping either yet. I did buy a m2 for parts but it was in too good condition to strip just a dry joint on the dc jack.
Did you try jumping 5v to the av port to see if it works that way? I was almost positive the board was just dead completely until I tried that, in that condition with a wire jumped from the 5v to the third pin on the av port it works. Only issue is the power button has no effect when pressed, the system is just automatically on. I'm trying to figure out what is shorting the system on the bottom board, I'm trying to figure out if there are any others with this problem that have identified a common resistor or chip that causes this no power issue.
Lucky you then getting it working. This one here is outputting video but it's just a black screen dead but stuck in game mode. All electrolytic caps are new. All chips are getting voltage but I may double check that. To be honest I have spent too much time on it already. There's no schematics available either.
I repaired a CDX unit with a similar fault couple months ago and it was issues with capacitors on the power board. (the power board is detachable so it wasn't too hard to work with it)
Oh can someone check c50 smt cap value for me mine was dead short it was a very grey colour. I have managed to loose it lol.
can you provide a pic of this cap / what you are talking about? I can look into it. I've had the problem before with the power board and it is a fairly simple fix. There is also a workaround solution I have used over the years. Here's what you do: 1) replace all power board caps. This is often the culprit but not always. I've never seen any other caps go bad in a CDX as contrary to popular belief they are very good quality and do not usually leak (like a Game Gear). 2) The power switching it controlled by one tiny SMD transistor and one of the large PNPs. The SMD transistor rarely goes bad but you can check it out. It is a tiny 3-pin (SOT package) near the large multi pin connector for the daughter CD board. If you are looking at the male pins of that connector, it is on the upper left side, closest to the cart slot. 3) This transistor switches a larger PNP when the power button is pressed. That PNP connects the DC-DC output to the +5v rail mains, which is connected to the AV out pin, like you mentioned. You are seeing it work because you are simply bypassing this circuitry. I have a pinout of the power board, this transistor, and more info I can maybe dig up later. The PNP outputs along the main power board connector. You can measure those 10 pins and you will see that when +5v is given to the AV port that +5v will appear on one or two pins from that power board. That is your PNP output that you can trace to the PNP on the power board. One of its pins is wired through another pin directly to that transistor. Replace both if you have to and it will work. Alternatively, if you want a super easy workaround, you can cut both traces to the power plug (there are 2, and they travel on the ASIC-chips top side of the PCB, above the metal housing for the power switch). Then wire your +5v from the DC-DC output to one pin and your AV_out +5v or (preferably) the actual +5v input on the power board to it. If you aren't getting +5v anywhere on your power board (less common issue), then you should definitely be OK with a recap. The reason your CD "walkman" mode works is because your DC-DC 3v output is still working OK. -Segasonicfan
OK...did you measure the pins on your power output board? Finding +5v on the DC-DC reg would be a GREAT place to start...
Awesome suggestion segasonicfan. I'll check the power to the transistor tonight and post tomorrow about what I find. It makes sense that something in that circuitry is faulty since there seems to be a short when switched on. If you come across the pinout let me know, would like to take a look and see if it helps me identify where the short is.
OK here's a complete pinout for you as well as a picture of the mini NPN (labelled Q1 on the PCB). The pinout reads from left to right, looking at the solder side of the boeard. http://i18.photobucket.com/albums/b134/Segasonicfan/Sega CDX/PSU Pinout CDX_zpszpdatsp7.jpg http://i18.photobucket.com/albums/b134/Segasonicfan/Sega CDX/PSU pins top CDX_zpsjxs2ga52.jpg http://i18.photobucket.com/albums/b134/Segasonicfan/Sega CDX/Q1 PSU Transistor CDX_zpszznpevda.jpg I checked c50 on a two boards and both show a 1.0ohm or less resistance. I think that is probably the way it is supposed to be. -Segasonicfan
Did you get my PM? If you are tired or pouring time into this I'd be interested in buying or trading for it. It sounds really friend and I could use the parts for another unit I'm attempting a repair on. -Segasonicfan
