Question about Audio Players & Recorders
McIntosh MC7106 Amplifier
When I turn the power switch on,lights come on for a split second,relay clicks,then nothing,any ideas?
Did you resolve this issue? Mine is doing the exact same thing
Posted on Jan 19, 2021
It can be a variety of reasons but I feel that your amplifier is shutting off after powering on. There is nothing that can be done from the outside but If you are familiar with basic electronics and can attempt to take a look I can try. Open the set after you have pulled off the power, then look into the set and tighten all the connectors and cords. Power on and see where the click comes and goes off. If the relay is not holding on then your protect circuit is shutting it off. Armed with a multimeter turn on the power and check if the main +B power is coming to the output stages.If there is momentary swithch on , then disconnect power and test the continuity in the output stages. If hsort open the leads to the output section and then power on. If the relay stays we have found the fault. you can go on to change the failed outputs. If however the outputs were tested ok, then your fault could be the relay or the protect circuit, Hold a rely for a moment to see if the amplifier powers on, if so check the relay drive transistor , the biasing to the stage. Try this out and I hope my advice helps. Good day
Posted on Jul 24, 2010
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Oct 19, 2013 | Mcintosh MC300 Amplifier
Wharfedale pro bx1360sd
I have had problems with this stereo mixer amplifier which had the symptoms of no sound output from either channel .
I opened up the unit and discovered that the amplifier was correctly amplifying my input signal up to a relay which switches the output through to the speakers .
This relay did not activate at all.
When the power switch is turned ON you should hear a click approximately 2 seconds later , if no click then there is a problem with the circuitry associated with this relay .
I traced out all the connections associated with this relay and made a circuit diagram .
The relay is a 24v relay and I will explain the way that I can see that this section of the amplifier works.
It has been designed to ;
This it needed because otherwise there is a current surge and sparks from the relay turning on immediately.
Q804 turns On Q805 which turns On Q806 to activate the relay .
Voltages on transistors
Q802 and Q803 2sc1815
Base 0V Collector 12.9V Emitter 0V
Base 12.9V Collector 0V Emitter 15.1V
Q805 2sc1815 (driver for Q806)
Base 0V Collector 7.2V Emitter 0V
Base 0V at Turn ON then after 2 secs increases to 0.7V
Collector 2.8V ( transistor is activated as a switch Turned Fully ON ( saturated) to turn on the Load which is the relay .
I have replaced the following transistors to fix my amplifier q805 2sc1815 and q806 2sc1815 .If you are going to use a different type of transistor it may not work and also the lead connections of a 2sc1815 for the collector and emitter are different to those such as on a 2n2222( transposed).
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