** Hi,


this week a old customer donated his long out of use Luxman SQ65 integrated, valve amp to me saying maybe I could fix it, sell it and make some money.

What an optimist, the amp is over 50 years old and still has most of the original valves fitted - plus 3 missing. Some of the valves are oddball, like 6DT8s phase splitters and 7868 noval outputs - neither type available in Australia.

The SQ65 is sort of famous for having both " motional feedback " controls and using cathode feedback in the output stage (a la Quad II ) so I persisted.

Put it on the bench for basic tests, gradually winding it up with a Variac and immediately found the main electros had depolarised. Next I found the bridge rectifier was only working half wave and even then with a huge voltage drop.

So I fitted a new bridge across the old one and after half an hour reached full AC supply without smoke so I let it soak for an hour or so.

My ESR meter informed that the main (dual can) filter electro was worn out - various others seemed still functional.

Then I checked the two output transformers with an ohmmeter and got strange readings from the first but the expected ones from the other. The first tranny proved to have an open primary winding - damn.

So fixing the thing for profit was completely out of the question.

I extracted the good output tranny and bench tested it using 240VAC across half the primary and a 16ohm dummy load on the secondary. Ran it for several hours until it got warm and saw no problems. At a pinch it might do as a replacement in my a Quad II workshop amp one day.

Based on Googling, I discovered that if fixed and working well an SQ65 has little value and there is simply no demand.

It will be going out on the next council clean up day.




..... Phil