Trying to fix a Kinergetics Research kcd40

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The tray motor definitely should not be active at all when you press play. That sounds an odd issue. Given that many weird faults like that end up being mechanical in nature then it would be worth checking the operation of all the 'load' and 'after load' switches related to the drawer and loader. Clean them, run a bit of paper soaked in ISO through the contacts.

If it plays, even for a second or two then the laser is at least working up to a point. That scope shot looks more noise than anything else but as I say, if it plays then the RF must be present, at least in some or other.
 
The door switch is a push button mounted on the board which gets 5V through a 22K resistor and shorts pin 33 of the MC68HC05 to ground when it is open and when it is closed. Voltages readings indicate that it is functioning properly.

The player definitely reads after I only fire it up for less than a minute then unplug it and let it sit for about 10-15 minutes. Getting it to play for a second seems to have no consistent pattern yet... I will keep trying to see if I can get it to put out audio for a brief moment when I do get it to play.

*update* I got it to read out again after I let it sit for just that amount of time and then held down the play switch as soon as I plugged it in... couldn't get any audio but the player was making very unhappy noises for about 5 seconds before quitting and doing its usual symptoms... like wtf? I wish I had some cold spray.
 
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At this point it would be worth identifying all the rails and looking at them on a scope to make sure they are all clean and correct and this being Philips based means there are going to be several.

Tbh this should really be the first thing to do with any fault, and this one has passed the point of inspired (or otherwise :D) guessing as to what the problems may be.
 
Voltages and ripple all look fine, the only rails that seem a bit odd are the +/-10V ones which read +12.35 and -13.35. The rails drop a couple volts when the player reads a disc and tries to play it. These rails have some ripple on them since they are "raw" supply. I will check to see how good the main filter caps are.
 
So get this now... I took a look at the schematic again and based on the symptoms I have been getting still concluded to a bad IC but as you said a disk readout likely suggested otherwise. But what about a transistor? Remember earlier I found an axial lead cap that was not reading very good? "2521 47uF"

Turns out that capacitor is coupled to pin 17 of the 8808 which is for the laser drive. Then there is a transistor CCS "6527 BC338". So my thought was what if this transistor was going bad after it warmed up? Nothing would work just as well obviously. I had a ZTX450 on hand which is the closest match I got to a BC338 and bingo!

The player is now playing CD's... well other than having the laser adjustment and focus now messed up in some sense and the RF out still just looks like a bunch of "noise" with some faint wave form in between.

But it works, thanks for the tips Mooly! This has been a big adventure, and hopefully this will thread will help others hunt down similar problems since this is not the first time I have found bad transistors in these players.
 
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If you have followed the manual to reset the presets you altered then that is about as much as you can do tbh.

Laser power is always an odd one with Philips, if they suggest using glass discs and looking for 50mv (or whatever) across a resistor on the photodiode array then I usually substitute that for setting the RF to around 1.2 volts peak to peak... but you need to see the RF clearly to do that ;)
 
If you have followed the manual to reset the presets you altered then that is about as much as you can do tbh.

Laser power is always an odd one with Philips, if they suggest using glass discs and looking for 50mv (or whatever) across a resistor on the photodiode array then I usually substitute that for setting the RF to around 1.2 volts peak to peak... but you need to see the RF clearly to do that ;)

Thanks Mooly! I decided to recap the DAC board while I had the player all apart, really opened things up! The player seems to skip on the first to second track every now and then so something is still off but other than that it sounds really good!
 
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