Well the title of the thread says it all really. It powers up but there is no sound. Connected an FM aeriel and from the tuning lights it seems to be picking up stations ok. When you try to adjust the volume the light on the right side gets slowly brighter, but then it suddenly goes back again. If that makes sense?

Craig

It makes sense alright.
You will probably find the lamp inside the LDR housing burned.
The lamp regulates the volume through the LDR's in a way so that less light gives higher volume.
Fortunately, a clever little circuit mutes the amp inputs if the lamp draws no current (burned filament), otherwise it would give max volume constantly.

Martin

So it could be down to just a blown bulb then? both the left and right bulbs on the volume do light up. Although the one for the Trebel does not. What does LDR stand for?

Craig

Peter :

Light Dependent Resistor?

Thanks Peter.

Craig

Exactly !

There are four of them housed in a little metal shielding together with a lamp.
Two for each channel (volume and loudness).

Martin

Martin, I can find two bulbs for the volume. these are in one section that is held in by two screws. Then there is a similar section which houses threee bulbs, for the Balance, Treble & Bass. All the bulbs are solder in place. or have I missed another set of bulbs?

Craig

Thats what I have found two of. As I say one has two bulbs in it the other has three. On both there is a small PCB which has the bulbs on. Nowhere can I find one with four as Martin mentions.

Craig

You will find it on the large main board, lift away the tonecontrol board and look for a little metal box, apprx 25mm square.

You can't see the light from the lamp, it's shielded to keep ambient light out or it would mess up the volume.

You can see it here (main board shown without the plastic frames etc.) 

Martin

Thanks for the picture Martin it helped a lot. So I have now found the box which houses the lamps. How do I get inside it? Don't want to go breaking anything else. What I have noticed is the box sits on a small PCB which is soldered to the main PCB. The box is very loose on the small PCB. Should it be like this? Tried to pull it up gently but did not want to use to much force.

Craig

You can solder out the box for an easier handling but you will have to use a little "controlled force" to open it.

Put an ohm-meter to the lamp first to confirm the diagnose first.

Martin

Well I tried to open the top of the box with it in place. Bad idea, I now have 4 broken LDR's. Are these all the same or do they vary in resistence? If they are standard I can just replace the old ones and the bulb at the same time.

Craig

Oh,

I think they are of the same value but I'm not 100% sure. If everything else fails I may be able to help you find a complete and working part but let's first know if the lamp was burned.

Martin

That would be the lamp that is now shatteredWell I did find these LDR'S on the web.

Craig