I’ll buy new probes. Then will calibrate and adjust the scope and will try again.
Even though the hf signal is not good, the player works.
Thanks for your help, really.
Hi again!! Yes it’s the correct test point. It wasn’t an issue with the oscilloscope or the probe. The problem was me. I had configured the oscilloscope to display the wave inverted (using a button that switches between a + and - for normal or inverted waveforms). Once I corrected it, a lot of the noise in the signal disappeared. That said, it still doesn’t look perfect, but that’s definitely the oscilloscope’s fault… it lacks sharpness:
Here’s the setup during audio testing:
It’s not in its final spot yet, but it’s sounding so good it knocked my socks off. In the upper left of the photo, you can see its sibling, the CD202 (and many other cd players I’ve repaired thanks to this forum.
Hello again,
After a few days of testing (I thought the player was completely fixed), it has failed again. While playing a disc (almost at the end), it stopped reading, and the disc stopped spinning. Even when I pressed PLAY, the disc wouldn’t spin anymore. I had to open it again and slightly readjust the focus offset and gain potentiometers, and it started reading properly again. The eye pattern looks like this (considering that my oscilloscope is not very good):
What could be causing this? Could it be defective potentiometers? Or perhaps a failing resistor in the focus circuit? I’m not sure where to start looking... Any suggestions would be greatly appreciated.
It is really difficult to diagnose faults like this at a distance. Given that it failed while playing and then crucially still wouldn't play at all makes me wonder if something like the laser driver transistor is failing... its a very long shot but its not unknown and I've had two or three fail in years gone by.
I'm not sure which version of RAFOC yours will use but they are all fairly similar. Some use a small T092 style transistor.
It is real stab in the dark but worth a try. This is from a CDM 1
I'm not sure which version of RAFOC yours will use but they are all fairly similar. Some use a small T092 style transistor.
It is real stab in the dark but worth a try. This is from a CDM 1
Thank you for your suggestion! It’s an interesting idea. However, I’ve noticed that when the issue occurs and I readjust the potentiometers, the ones I adjust are related to focus (focus offset and gain), not the laser. If the laser driver transistor is failing, how could that affect the adjustments related to the optics?
The transistor tends to fail in an intermittent way and so the laser current and output would alter. You can think up all kinds of scenario but that doesn't mean it happens. So laser output varies and you partially compensate by altering other things... its plausible but doesn't mean it happens.
I just know I've had those transistors fail, and while it seems an unlikely fault it does happen. Its quick and easy to replace and if nothing else it removes it from suspicion. As I say though, its a long shot.
I just know I've had those transistors fail, and while it seems an unlikely fault it does happen. Its quick and easy to replace and if nothing else it removes it from suspicion. As I say though, its a long shot.
Your reasoning makes perfect sense, and it really seems likely that the issue lies with this transistor. In fact, when I adjusted the eye pattern a few days ago, its amplitude was 1.5V (as you can see in the photos, where each division on the oscilloscope corresponds to 500mV).
Yesterday, when I adjusted it again, the amplitude was around 1.2V.
This morning, after the reader failed again and I readjusted the focus, the eye pattern was back to 1.5V.
So it’s clear that something is causing fluctuations in the laser's power, which makes your suggestion about the transistor very logical.
That said, I understand that it's not ideal to mess with the output of this transistor since it directly drives the laser. I've also been warned multiple times that any static discharge could damage the laser.
Is there a real risk of damaging the laser due to static or any other issue when replacing this transistor?
2 cents ...
If I'm not mistaken, the CD303 is perhaps the most 'romantically nostalgic' CD player in the world 🙂
If I'm not mistaken, the CD303 is perhaps the most 'romantically nostalgic' CD player in the world 🙂
Probably hehe 😄 I already have a working CD202 unit (and I hope it lasts for many years), but this CD303, even though internally it's the same machine, has something magical about it.
Providing you use good practice there should be no issue. Make sure the player is totally disconnected from both mains and its RCA outputs and that the soldering iron is proper mains earthed one (or use a gas iron).
I know you mentioned recapping. That cap on the base of the transistor is actually the number one failure item but I'm assuming that one was replaced.
Thanks for the soldering advice. I have a gas soldering iron, so I'll use it for this task.
Regarding the capacitor, yes, I replaced it. It's an electrolytic 68µF one.
Next stop: transistor replacement!
Just a quick follow-up question... The transistor in question, according to the service manual, is a BD226. If I can’t find this exact model, I’ve identified a few potential replacements based on its specifications:
BD139 (lower current handling, but seems common)
TIP41C (higher current and power dissipation, TO-220 package)
MJE3055T (similar to the TIP41C, also TO-220)
Would any of these be a viable replacement? Or is there a better option I should consider? I want to ensure the replacement works reliably without risking damage to other components. Thanks again.
It's the original value:
Please take another look at my previous post; I have a question about which transistor to use.
Also, I've spent the whole morning turning the player on and off, and so far (with the current focus potentiometer settings) it hasn't failed, and the eye pattern looks nice with a 1.5V amplitude.
The only downside is that the gain potentiometer is getting closer to the extreme end. If it keeps going like this, there will come a point where it can't be adjusted anymore. I have faith it's all related to the transistor hehe.
Also, it might be worth mentioning that these focus misalignment issues started after I reflowed the cold solder joints on the servo board. When I did that, a problem I had with the board (the player would stop working when I moved it) disappeared. After reworking the solder joints, that issue was fixed, but the lens misalignment issues appeared.
Last edited:
Hello again! I've been very busy over the holidays and haven’t been able to work on the 303. Today, I finally managed to replace the laser power transistor, but unfortunately, the issue still hasn’t been resolved...
It seems the player randomly goes out of adjustment depending on the time of day. The only way to get it working again is by tweaking the focus potentiometers. Once adjusted, the eye pattern looks incredible (I now have new probes).
I’d bet these issues are related to a fault in the servo. As I mentioned in earlier posts, these random misalignment problems started after I reflowed all the solder joints on the servo board. Could it be overheating of a component?
Right now, it’s playing a disc without any problems, so it seems the player itself is fine. The only thing I can think of is a component that heats up or cools down over time and changes its characteristics.
What a headache, haha!
I’ve noticed that when I remove the metal chassis from the bottom of the CDM0, all the issues seem to disappear. I’ve played some discs with the chassis in place, and in every playback, there have been moments when the player completely stopped (although pressing play would restart the disc). However, if I remove that bottom chassis, the discs seem to play without any problems.
I’m not referring to the bottom chassis of the player itself, but rather a very thin metal plate that protects the underside of the CDM0.
It’s really strange, to be honest... I'm going to play a few discs with that chassis removed... I hope there are no issues so I can confirm my theory.
I’m not referring to the bottom chassis of the player itself, but rather a very thin metal plate that protects the underside of the CDM0.
It’s really strange, to be honest... I'm going to play a few discs with that chassis removed... I hope there are no issues so I can confirm my theory.
It does sound an odd fault. I guess you need to be 100% certain it is related to this plate... which I can't just visualise tbh
First disc played with the chassis in place -> Playback stopped at a random moment (this time during track 2).
Played the same disc again but without the bottom chassis -> Played all the way through without any issues.
Third disc played without the bottom chassis (a different album this time) -> Played all the way through without any issues.
It’s likely that this metal plate is creating some kind of contact or short somewhere that I can't see. At first glance, it doesn’t seem to be touching or bridging anything.
As you said, it’s a strange issue. At least I’ve gone a week without experiencing the issue where I had to constantly adjust the focus gain and offset potentiometers.
I'm taking it easy... I have many Philips players, and the one I'm using the most is the CD202, which you yourself helped me repair. Once I figure out what on earth is wrong with this CD303, I'll place them together so I can use both. They’re wonderful machines, despite the headaches they bring, haha!
That would be the only thing that would make sense. Maybe try covering it with thin card or paper on the side that goes to the PCB as a test.