1 plus 1, interface 121-c playing about 6db lower

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Gary Smith2007-07-05 08:30

Hi Andy I have a pair of 1+1\'s with the red medallion interface. One side is playing 6db than the other. As there aren\'t any repair places in my area that have even heard of Acoustat let alone repaired one it\'s been a challenge to get this repaired. I tried sounds like new without any response and after reading some of your answers it may seem that possibly a transformer has gone or is it possible some capacitor or resistor has. Not sure who to ask. I see the parts on ebay listed by sound valves and am thining of bidding on the bias transformer or high frequency..or what would an educated guess be to look at? I have checked all the fuses..put another 121c on the speaker...works fine with that from a pair of threes I have but would like to get this one working if I can so I don\'t have have 1/2 a pair not working. Any suggestions?? Gary


Andy Szabo2007-07-27 23:30

If one speaker is playing lower in volume than the other, but otherwise sounds ok (no distortion or break-up) then I would suspect a problem in the bias power supply. It could be the bias transformer, but I doubt it. Those usually fail completely, rather than operating at a reduced level. I would concentrate on the 5 diodes and 5 capacitors in the bias multiplier. If one or more of those components is bad, it will reduce the bias voltage, and hence reduce the volume. There are some technical briefs on the bias power supply on this website, with instructions on measuring the bias supply. Your first step should be to determine if the bias voltage is low. Under \"available parts\", a source is listed for the diodes, and the capacitors are not generally too difficult to find (try Newark.com) Good Luck, and write again if you need further help. This problem can be fixed!

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