hi - im using the above - all line ins ok but no phono- are there different types of card for MM etc?
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That looks to be what Quad call the 'Disc Adapter' which is just a passive circuit. It is the left hand section shown here. The passives look to be the feedback network and RIAA equalisation.
The active high gain stage is the module on the right. Is that fitted?
The active high gain stage is the module on the right. Is that fitted?
I've no easy answers I'm afraid. You are going to have to trace the signal through, ideally using a scope and generator. At the very least check the DC conditions are correct on the transistors and check for continuity from the disc input to the input caps on the transtor board. Then check the output line from C304 and 305 back through the board of passives and finally to the input selector switch.
Of course also check the supplies to the board before doing anything.
Of course also check the supplies to the board before doing anything.
Carefully locate and measure the DC voltage on the collector of TR302 and TR303 on that preamp board. The collector is the 'top' terminal of TR302 on the diagram with 5.4 volts on it. That one voltage will tell you if that stage is essentially powered up and operating correctly.
There are 4 preamp boards with 2 transistors each. If both channels are not working , look at the power supply
If one channel is working or high level inputs working , a transistor may be dead.
Does the power ind light up?
Check dc voltages on the large caps by the transformer.
If one channel is working or high level inputs working , a transistor may be dead.
Does the power ind light up?
Check dc voltages on the large caps by the transformer.
this might sound dense - but i cant get to that board - i assume it needs to be plugged in to measure
It does need to be plugged in and on 🙂
It looks possible to measure on the 330nF caps, one end of which does go to the collector. Just be careful not to short anything although you would be unlucky to do damage around there even if you did.
It looks possible to measure on the 330nF caps, one end of which does go to the collector. Just be careful not to short anything although you would be unlucky to do damage around there even if you did.
many thanks for your patience sir - so i can measure from the cap to earth/chassis ? ac voltage?