been asked about this problem with a Quad 405-2 amplifier
thought some of the boffins here might know whats wrong so first



I have a lovely old Quad 405/405 Mrk 2 amps which I had biamped with an Audiolab 8000C I wanted to upgrade
so bought 2 of their upgrade kits containing capcitors and new opamps, etc, the Quad 405/2 works like a dream,
although not technically minded, if shown where and how to solder and replace its not a problem. Dare i say that
this problem is nothing to do with Net AUdio. The guy has been very helpful with me and very patient. But on
first power up. It wailed very loudly in the right speaker, coughed , spluttered and died. So I sent the whole
boards back this time to Dave at Net Audio, and he fixed for a minimum price. I got the boards back yesterday and
fitted them back into the chassis connected to the heatsink, all correct and seated properly The boards were
checked by Dave and so no problems there.
He has told me to check the ohm readings with a multimeter to the negative and positive teminals on the
speakers. The right side reads, 3.12 ohms, and the left side 0.9ohms. The DC voltage on either side left and
right, into the boards from the transformer is 105 volts, so no probs. But Since the wailing was down to my wrong
placement of some Capacitors i knew that the first time it wailed it was my fault. But I think to add into the
equation, that the right sided speaker terminals are shorting themselves?? . Might that account for the different
readings , left and right. It is an old 405 with those spring clip terminals, so if a short peice of wire has
somehow jammed inside the housing snd is causing a problem, would this reading of 3.12 ohms, be an indication of
that?



so to check if its the clips wire unsoldered and checked

With the wires removed from the boards, (where the spade connectors fit in to each seperate board for left or
right)

the readings without wires on the left is 0.21 Ohm and Right 3.20 Ohm

and connected is left 0.15 Ohm, and right 0.48 ohm




any ideas?


--
Dave
www.davewhitter.myby.co.uk

Music is Art - Audio is Engineering
Steam is Fun