Visitors to my site will already know how much I like the Quad 405. A recent conversation with a customer inspired him to acquire some Quad gear, including this lovely, original 405. In this article, I cover servicing a Quad 405, the Liquid Audio way.
Talk about great sounding amps, and this particular 405 is completely original, with its original capacitors and connectors. The owner wanted me to freshen her up and fit some RCA connectors, so that’s what I’ve done. Let’s look briefly at what’s involved in a Quad 405 service like this.
I try to keep this simple, a freshen up is not a full restoration. A service like this focuses on reliability improvement and bang-per-buck sonic gains. I start by carefully inspecting the 405 and looking for any signs of parts failure or earlier poorly executed work.
The Thermal Interface
the next step involves removing both amplifier modules and cleaning all the old thermal compound from modules and heatsink.
Refreshing the Modules
The modules themselves just needed a little freshening up in this amp. Depending on what my customer asks for, I’ll do more or less at this stage of the overhaul. In this case, the original ERO capacitors came out, two of which were absolutely dead.
I pay careful attention to fasteners. In this amp, some of the transistor mounting fasteners were not tight, and the module fasteners were barely finger tight. I remake the solder joints under each transistor after doing this, to remove stresses. Lastly, I clean each board, removing flux where necessary.
If the customer wants something more like a restoration, I’ll remove the output devices, possibly replace them, and remake the thermal interface with silicon thermal pads.
Installing RCA Connectors
Finally, I installed some RCA connectors on the back panel. Whilst not strictly necessary, the owner requested it here.