Mission DAD7000 CD Player (Philips CD104) No Audio....Do I or Don't I ?

Well, you've covered the griplets, now it's time to measure voltages. I would warn you that if this player has TDA1541s in it as the DACs, they are incredibly intolerant of wrong/excess voltages and die at the drop of a hat. I don't think they do though. 

Hi Catho,

It has a pair of TDA 1540P

What I do recall is that CD104s have muting relays: can you hear them operating? 

Yes it does, a pair of reed switches inside a coil. I can't hear them operate but that said I'm not sure I could physically hear the reeds anyway. I've put a meter across the coil but there doesn't seem to be any voltage there ......

EDIT... scrap that, 4.8v at the coil (meter lead issue)

Well well well, in the early 90's I worked at Mission Electronics in the serviced dept. and these were almost a daily item in for repair. Back then, the only faults were no TOC, no sound and intermittent operation. It was always dry joints. They are on the through-pcb earth points as you know. There is no need to drill as a piece of wire should fit through. But there are load's of them so be prepared for some work. You may also see a potted grey box that was a Mission add-on to filter the sound, to help smooth off the rather stepped sinewave from the decoder. Worth checking to see if normal audio is going into it from the decoder pcb.

Another thing was broken wires at the connector plugs, but only if a unit had been serviced too frequently. Dry joints on the PSU regulators can also give trouble.

Hi Andrew,

Memory lane for you then  ? 

When I say 'drilled' the griplets out I actually meant clearing the holes of excess solder with a precision screwdriver so I could get the new wire link through. 

I've just tried the audio before the filter but nothing there. 

The one thing that made the CD104 stand out from its contemporaries was its use of 4x oversampling, which was an improvement over just about everyone else at the time who were using 14-bit DACs as the output device.

Marc, unlikely I know, but does this player have a digital output? If it's reading the TOC and 'playing' then there's really very little to stop audio coming out, unless it's muted in some way but connecting a digital output to an external DAC would prove a lot. I'm still minded to think 'vias'. 

Buried in the store, I have the manual for the CD104. I'd still be inclined to measure voltages. 

Hi Catho,

Unfortunately this player doesn't have a digital outlet but I think 'muting' is part of the story as it appears to be playing fine and it's both analogue outputs that are affected.

I've checked and checked again and again for dry joints on both boards and the PSU and done some re-flowing just to make sure, still no joy.

'vias'  through connections ? sorry if being thick  ? 

Hi Marc, if soldering the joints and vias makes no difference, then I'm inclined to agree with Catho and say it's time to check for some voltages. It could be that the output is muted, and I think a couple of transistors short the outputs during mute. You really need the manual for fault-finding to be honest though. It is strange how swapping the decoder panel didn't change things, bit of a coincidence for both panels to have the same fault. It could even be worth soldering up the other machine and see if the laser comes to life.

BTW, you are using a standard "red book" CD to play aren't you?

I've just uploaded the Philips CD104 service manual to the data library, which I believe has been stated to be an equivalent. 

Posted by: PYE625

It could be that the output is muted, and I think a couple of transistors short the outputs during mute.

It appears to be a couple of reed relays opening.

Also, the CD104 didn't have remote control, but there was a model above it that did.

Excellent Chris, thanks.  ? 

Also just uploaded the May 1992 'Television' mag servicing guide for the Philips CD104

Posted by: PYE625

BTW, you are using a standard "red book" CD to play aren't you?

Not being any expert here I presume you mean 'standard pre recorded' CD ? if so, yes.

I had a CD104 for years and it was a lovely machine but in the end, not only did excessive griplet failure become an issue but mine had a dead spot on the turntable motor, which I worked around by opening the tray and pushing the turntable around with the rubber end of a pencil!

Thing is, those damned griplets/vias were becoming an issue even in the late 80s.

Looking at the service data (page 54) I can see that it appears to have 10 griplets on the decoder board, is that correct or have I missed some ?

Posted by: Marc

Posted by: PYE625

BTW, you are using a standard "red book" CD to play aren't you?

Not being any expert here I presume you mean 'standard pre recorded' CD ? if so, yes.

Yes, just a bog standard CD.

I remember the reed-relays now ! Little glass cylinders within a coil. Been so long lol.

It's been stated about voltages...that has to be your next move. It's also worth scoping the supplies to see if there is excess noise on them. Sometimes the regulators can produce noise on the supplies, sometimes caps.....I never had cap failure but that was 30 years ago....when you look at the circuit, it's worth trying to disable the mute circuit...but get those supplies checked first.

I shall recommence battle tomorrow and start by checking the voltages from the PSU.