On 25/06/2017 9:16 PM, Phil Allison wrote:

** 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.


**Weird. Most Luxman valve stuff fetches really good money.


--
Trevor Wilson
www.rageaudio.com.au

Trouble is though fixing a transformer is not a trivial thing, and if the
system has valves no longer made it is going to be a nightmare as well.Was
this the one which was one of the first pcb mounted valve devices that
tended to get warped boards due to heat? It was a long long time ago. My old
Rogers was point to point wired, in fact still is and still works, but then
its a much lower powered device and although itsounds nice I doubt it would
cut it against relatively cheap units today, but is good as a foot warmer!
Brian

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"Trevor Wilson" wrote in message
...
On 25/06/2017 9:16 PM, Phil Allison wrote:

** 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.


**Weird. Most Luxman valve stuff fetches really good money.


--
Trevor Wilson
www.rageaudio.com.au

Brian Gaff wrote:

------------------------

Trouble is though fixing a transformer is not a trivial thing, and if the
system has valves no longer made it is going to be a nightmare as well.



** The valves are not the issue - 7868s ( 9 pin ) have an equivalent, the 7199 octal type. Means fitting new sockets.

The 6DT8 appears to be a 6.3V heater version of the 12AT7 - so rewiring the sockets is all you need to do.

The output tranny is a deal breaker, but the overall parts cost and time needed are way out of the ball park.


Was
this the one which was one of the first pcb mounted valve devices that
tended to get warped boards due to heat?


** All point to point hand wired - very nice IMO.


It was a long long time ago. My old
Rogers was point to point wired, in fact still is and still works, but then
its a much lower powered device and although itsounds nice I doubt it would
cut it against relatively cheap units today, but is good as a foot warmer!
Brian



** Did some repairs on a Rogers Cadet II amp and pre late last year.

Neat little system.


..... Phil

"Trevor Wilson" wrote in message
...
On 25/06/2017 9:16 PM, Phil Allison wrote:

** 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.


**Weird. Most Luxman valve stuff fetches really good money.


There is one currently on e-Bay for GBP 1954.29

Iain

Iain Churches wrote:



There is one currently on e-Bay for GBP 1954.29



** Stale news.

TW mentioned it and I answered him.

Pays to read a thread before posting.