I have purchased a "faulty" Kenwood A-47 amp from E-Bay. The amp is now functional, I have put larger heatsinks on the dreaded main amp driver chips. My only problem now is that the electronic selector switch doesn't work. I input a signal to the Aux input, move the selector switch (the indicator lights change) but the input continues across all the inputs selected by the switch. Anyone any ideas?
Stuart Preston.
Stuart Preston.
A quick look at the circuit shows this uses common CMOS bilateral switches like the 4016/66 and 4053 etc etc but your problem may be elsewhere.
You need to look at the switch handling say the Aux Input and check if the logic control signals are changing state as you operate the selector...... but I also see this unit looks like part of an integrated system where everything connects via multiway ribbons. Could it be that it all needs to be connected up to the rest of the system.
I can't see a normal Aux input (or CD input or Tuner input) on the amp unless you mean the one marked Record/Play in although the circuit shows an Aux In.
I suspect this will not be easy to trace.
You need to look at the switch handling say the Aux Input and check if the logic control signals are changing state as you operate the selector...... but I also see this unit looks like part of an integrated system where everything connects via multiway ribbons. Could it be that it all needs to be connected up to the rest of the system.
I can't see a normal Aux input (or CD input or Tuner input) on the amp unless you mean the one marked Record/Play in although the circuit shows an Aux In.
I suspect this will not be easy to trace.
Thank you for your valuable comments. My unit does not have the jumpers on the adapter input, and I omitted to say that the input that works, is the adapter in. I bought this as a single unit and as you say I do not know whether the other units need to be connected or whether the system control needs to be connected. It looks like a no go situation, I may just use an input selector box with the single input that works!! I just thought someone else may have encountered the same problem. Thanks again, I have searched the web for a solution but because it was part of a "system" there seems to be no information.
If you fit the link I think you might find the other sockets to the left might at least work. The adapter in/out looks to be a link between the pre and power amp sections.
Will give it a try!!
Thanks again for your suggestions, I have the service manual but there doesn't seem to be a mention of the link on the adapter sockets.
Thanks again for your suggestions, I have the service manual but there doesn't seem to be a mention of the link on the adapter sockets.
I can see the sockets on the diagram but after that the scanned copy I have (and you are probably looking at the same) is so spread out and with bits missing that I can't trace it through. I would say if you are feeding a signal into the adapter sockets then that is probably feeding after all the input selection.
The block diagram seems to confirm that. The adapter link is between the preamp/input selector and power amp. So it behaving as expected I'm afraid.
The block diagram seems to confirm that. The adapter link is between the preamp/input selector and power amp. So it behaving as expected I'm afraid.
Thanks for taking the time to look at this for me. I will try connecting the adapter in and out to see what happens. Same poor quality service manual as yours! If I have no joy I have an old RCA switched input box which I can connect up and use as a selector. Doesn't seem a bad amp except for the very hot chips in the main amp.
One possible option might to be experiment with adding input sockets (or flying leads and RCA socket which would be easier) to what look like the inputs that come in via the ribbon. There are Tuner, CD and Tape inputs on there.
Adapter connected, input selector works!! I will now implement your suggestions, I will find the inputs on the connectors on the back ie Tape A and
B and CD connector and re route them to either unused or new RCA sockets. Things are looking much better thanks.
B and CD connector and re route them to either unused or new RCA sockets. Things are looking much better thanks.