Quad 405 Tansformer rumble ....
Some older 405's have a problem with the transformer. It produces a rumble (not in the speakers but in the transformer itself).
There is no way to fix this problem except by replacing the transformer.
Of course you can order a new transformer from Quad but this is a quite expensive solution. Therefor this alternative: one can fit a toroidal transformer (300VA 2x 35V). This also offers the advantage of better stability and somewhat less noise, limiting the cost to about 90 Euro.
The only problem: to fit it in you will need a special mounting plate. I found one on Ebay in the UK, Stuart Adamson had them made by a steel manufacturer. I also had to move the fuse because it was in the way (see the picture).
But now my 405 works fine again ;-)
PS. The transformer you need is a Toroidal 2x 35 or 2x 36 Volt, 300 VA (not less!). Make sure it will fit in.
A 300VA toroïdal transformer and the mounting-plate are now available in the Dada Electronics Webshop.