Model 1 Sega CD LED problem

Hello, I’m looking for some help with my model 1 SCD. Everything works perfectly except for the green “READY” LED, which never comes on. The red “ACCESS” LED works perfectly, disc drive works perfectly, it reads games perfectly, but I need that green LED to work! We tried testing some resistors after reading up as much as we could on the issue but our multimeter sucks. However when we touched the legs of the green LED, it illuminated. So I think the actual LED is fine. I’m hoping someone can help me figure out how to get it working whether it’s replacing a resistor or transistor (and where to buy them) or just jumping the board with a wire and a resistor in case a trace isn’t working. Any help would be greatly appreciated. I’m located in Maryland and am also interested in having someone experienced Re-cap this thing if anyone is in the area. Part of the reason the model 1 is so awesome is the green and red LEDs and it’s driving me crazy.

 

Unless someone tells me some other solution, I guess I'm going to try to replace the resistor R5. Service manual says it is 160ohm, 1/10W, 5% tolerance. Will any of these products work?
https://www.digikey.com/products/en...k=1&rohs=1&quantity=0&ptm=0&fid=0&pageSize=25

Using the same searching function on mouser,
https://www.mouser.com/Passive-Components/Resistors/_/N-5g9n?P=1z0wnk8Z1yxpkfvZ1z0x6fr
The products are listed as 50v, 75v and 150v "voltage rating." What does this mean? The service manual doesn't list a voltage rating for the part.

Am I going about this the right way? I can't seem to find the other kind of resistor (oval thing with stripes on it that goes above the board using long legs) with the correct values. Nor do I know what "VCC2" is.

For the record, I've tried cleaning the shit out of the genesis and cd connectors, the a/c adaptors are all first party and functioning properly, I've tried using other genesis consoles, the green light still never comes on.

 

The first thing u need to do is get a working multimeter. Then check R5 and R7 to make sure they work and meet the listed spec. Also using the diode function on your multimeter is a good way to check LED are working. The voltage rating on resistors just tells u the maximum they can handle. As these are 5V leds, anything rating above that is fine.

Don't go blindly replacing components until u have identified the broken part.

 

Thanks for the reply. Can you tell me what exactly a transistor does and how to test/replace it? The service manual doesn’t list specs, just a part number. (TR1 and TR2)

 

TR1 and 2 part numbers are shown on the pic you posted. You would just replace with the same thing (or look up its datasheets and check the specs there).

Transistors basically work as a switch.

 

So like this?

https://alltransistors.com/transistor.php?transistor=59952
https://www.mouser.com/Semiconducto...0z7ptZ1z0y4diZ1z0w6xvZ1z0wa4fZ1z0wajcZ1yyzhud

 

As above. The transistor here is acting as and internal switch. When a small current is applied the base, current is allowed to flow from the collector to the emitter. In this case, a signal from pin 65 on IC2 passes through a 4.7k resistor (R7) to the base of TR1 and allows current to flow through R5 and LED2 to ground.

First get a digital multimeter and test the resistance of R5 and R7 to rule out bad resistors, then use the diode test function to test TR1. Here's the data sheet for TR1 http://pdf1.alldatasheet.com/datasheet-pdf/view/5852/NEC/2SC1623/+_7W_uICzZ8yE9vtY+/datasheet.pdf
Also use the diode test function to test the LED
R5 and R7 are 160 Ohm 1/10w and 4.7k 1/10w respectively.

Good luck.

 

Thank you very much for the replies. I’ll report back!

 

Ok so I’m talking to this guy who says he had a similar issue that had to do with the console not detecting his AV cable. Does the green READY LED have anything to do with the AV cable being plugged in? I remember the original Xbox flashed orange if the AV cable was unplugged. I already tried plugging in a different cable and it still doesn’t come on.

 

No that has nothing to do with it. The console has no way of knowing if you have an AV cable plugged in.

If the LED works I would check the transistor next.

 

Replaced R5, R7 and TR1 still no luck. Trying new caps on C45 and C46 just cuz they are close to the components. Kind of at a loss here...

 

While you’re at it you should replace all the caps in the unit. Both the main board and power supply. They will go bad if they haven’t already.

 

Yeah we’re going to just not tonight. I got a cap kit from console5.com They gave me a huge line of 10uf 50v caps but I don’t know what they’re for. The most common original caps are 10uf 16v so we’re using the supplied 10uf 25v ones for c45 and c46 just bcuz they’re close in voltage rating. Duno why they gave me so many big 10uf 50v ones...

 

In other news the fluke multimeter just arrived. We still don’t really understand how to test transistors if anyone wants to give detailed instructions I’d appreciate it. R5 and R7 are both reading accurate resistance now after replacement

 

Still no luck. Only way we can get the green LED to illuminate is while powered on, connect a small wire from the negative pin of the LED to the ground border. What the hell? But then it stays on even if a genesis game is inserted which I don’t think is correct. I think if a genesis or 32x game is inserted then no Sega CD lights should be on

 

That sounds like either the transistor is dead or the pin that drives it.

 

The light stays on because u have bypassed the switch (TR1) and directly grounded the LED.

Use u'r multimeter to test for a voltage at R7 when the mega CD should be displaying a green light. If u get a voltage then th IC pin is working.

The voltage rating on caps needs to be above the voltage applied to them. In this case it's usually 5V so either a 16v or a 50v cap is fine.

Use the diode function to test the legs of the transistor. On an npn transistor (unpowered) connect positive to Base and negative to either collector or emitter, both should display a voltage. Now reverse the probes (positive to emitter or collector, negative to base) both should read open circuit. Now place the probes on collector and emitter. This should also read open circuit.

 

The transistors have 3 legs, two on one side and one on the other, which legs are which?

Before we quit last night, we could have swore that the service manual is wrong and that pin 65 goes to a different resistor and transistor. If I recall correctly, it appeared that following the traces it goes to R3 and then TR2 and then to the LED. Could the service manual be wrong? Very frustrating

A big sincere THANK YOU to everyone replying to this thread by the way. I appreciate the help so much and look forward to being able to learn more about circuitry especially regarding these old consoles that I love so much.

 

What if I Jerry rigged a big wire going from the LED attached to a transistor, resistor, and to pin 65, bypassing the board? I know my components are SMD but we could probably make it work...

 

The service manual should be correct. Don't go altering your console until u have identified the problem.

Do u get a voltage on R7 when the console is powered and the green led is expected to be on? Check this first.

The transistor is an npn transistor in a sot-23 package so the pins should be as follows