Problem with vintage player

[Juien]

Hi all!

I have a very old Philips CD104, that has the following problem when connected to the amplifier: when I turn the amplifier's volume knob up or down I can see the right speaker's cone moving. This does not happen with any other player I have so it cant be amplifier related.
Apart from that, the player sounds beautifully, and I cant hear any hum or strange noise.
Any ideas what can it be and what can be done?
And can I use it like this until I get it repaired? I mean is there any danger for the amplifier or speaker?
I really love this player's sound and would hate to part with it.
Thank you very much! Any advice would be much appreciated.

 

[poynton]

Change over the audio leads from the cd player.

Does it still happen with the same speaker or has the effect also changed sides?

If the effect changes sides then you have a problem with the cd player - probably a small amount of DC voltage on the channel.

If it does not change sides then the fault is in the amplifier.


Andy

 

[Juien]

Thank you for answering!
I will try to do that once I get home from work.
Anyway, if it proves that the effect changes sides and there is that amount of dc voltage - is there any danger? And what can be done?
Thank you again!

 

[Juien]

So, I swaped the audio leads and the effect went to the left speaker, it's definitely the player

 

[poynton]

Do you have a test meter ?

If you do, then measure across the output of the affected channel and see what the voltage is. It should be zero but may be a few millivolts.


Andy

 

[Mooly]

Before you do anything I would try and measure any DC offset coming from the players output sockets. There should be zero volts.

I haven't got the manual in front of me but this just might be something fairly simple as I think the player will have an AC coupled output which means that should always be no DC voltage at the output.

Didn't these players suffer from 'griplet' issues, called rivets or bushes here:

~ Classic CD Player Modification & Modernisation ~

 

[Juien]

Unfortunately, I dont have a test meter.
Searching on similar issues on the internet, I also found out that it may be a dc offset and a dead output coupling capacitor?
Can it be fixed or is this player dead?

 

[Mooly]

Yes, it should be fixable assuming that its a 'normal' fault, and that it is not caused by something like spillage or the unit having an unknown history such as having been bought second-hand.

Without basic test equipment it all becomes guesswork. You have to be able to measure.

 

[Juien]

I will get a guy to do some measurements.
Anyway, the more I read about it the more I am convinced that this is related to the output coupling caps. How do I know which are those?

 

[Mooly]

You look at the service manual, thats how

https://www.hifiengine.com/manual_library/philips/cd104.shtml

 

[QSerraTico_Tico]

Output caps could be leaky. It is a VERY old player.

 

[Mooly]

Have you owned this player from new or does it have an unknown history ?

I'm wondering if someone had made a misguided attempt at modifying this by possibly shorting out the caps.

 

[Juien]

No, I bought it second hand, so I dont know its history, but the player looks very clean on the inside, as well as on the outside.
I also read that some people use to remove the output coupling caps to "improve" the sound.
I wonder if this is the case with this player.
Unfortunately, my tech knowledge is zero and I am having a hard time finding someone who really knows how to troubleshoot a cd player.
Now I noticed that I mistakenly said cd104 in the thread title, in fact is cd304. Anyway, they're kind of similar inside.
The player has a volume control on the rca output, and when I lower the output volume, the effect does not happen.

 

[Mooly]

The service manual will show the location of those parts on the circuit board and it should be easy to see if they have been linked out.

 

[Mooly]

This is the CD304. You need to look and see if these have been linked out.

 

[Mooly]

If are confident to take the top off and have a look and if you also have a multimeter then we can tell you how to test it and check if those caps are linked out.

If they are linked under the board then you may still see them in place, but the meter tests will show if they are shorted out.

There is also a slim possibility that DC offset could be caused by a faulty muting transistor. Again with a meter its easy to test what is happening.

 

[Juien]

Thank you very much, Mooly. I will have a look and let you know.

 

[Juien]

I didnt open the player yet, but just noticed something: until now, I used the amplifier with source direct enabled. If I disable source direct, I dont notice that effect anymore.
I suppose the amplifier engages some protection circuits once I disable source direct.

 

[Mooly]

Most likely the source direct signal path employs DC coupling, and defeating it introduces a series cap into the signal path within the amp.

 

[Juien]

Well, I didnt get to inspect the player anymore, as an acquintance of mine bought it from me that very same day.

Instead, I got a CD303, fully functional, however I noticed the following anomaly: after about ten or maybe more minutes from starting to play, I noticed that the top cover starts to somehow vibrate. I can sense this while touching it. It is strange that aside from that faint noise from the transformer I cant hear anything once I lift the cover. That vibrations occur regardless if the player plays a disc or not.
I suppose that vibration is somewhere inside and the cover, being very thin, amplifies it, so to speak.
Any ideas what can it be?