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Sansui AU-919 Needs Love.

I stll have 4 cables on F-2839 (driver board) connected. This is another board that has been worked on by someone else so it is also very suspect. Will look at removing those 4 when I get back home.
 
Ok so the last 2 wires that I haven't disconnected are 2 blue ones to F-2928.

PCB-revision.png

So I'm thinking that it is these 2 wires with the brown one being I guess 240 input to the transformers.
P1040220.JPG

So of disconnected then this should be the last of the secondary windings connected? The fuses are confusing me because they suggest to me that the blue wires should be mains power to the primary coils. Then there is a blue wire on the top left of F-2928.
Just need to be sure I am disconnecting all of the secondaries.
 
Oh well, even with the 2 blue wires disconnected I still get a bright bulb. I don't think there are any more wires from the transformers to disconnect.
Looks like a bad transformer then.
Any ideas how to definitively confirm this.
Should I kook at pulling the transformers from the chassis?
 
So, all the secondaries are literally disconnected (not just 'fuses removed') - in other words all those you can see in the posted snip of the power supply - for both transformers?

PT701 - 2 x Yellow, 2 x Purple, 2 x Blue

PT702 - 2 x Orange, 2 x Yellow

And the bulb is 'full bright'? - not dimming at all?
 
Hyperion said:
So, all the secondaries are literally disconnected (not just 'fuses removed') - in other words all those you can see in the posted snip of the power supply - for both transformers?

PT701 - 2 x Yellow, 2 x Purple, 2 x Blue

PT702 - 2 x Orange, 2 x Yellow

And the bulb is 'full bright'? - not dimming at all?
Click to expand...


Yes all the above wires disconnected. Bulb is at what looks to be full brightness.
 
Sorry for all the stupid questions. :(

Finally, Are you sure the voltage selector plug is correctly orientated.

Check the resistance reading for the primary winding again?
 
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Hyperion said:
Sorry for all the stupid questions. :(

Finally, Are you sure the voltage selector plug is correctly orientated.

And the 2 blues and 1 brown - unplugged?
Click to expand...

2 blues unplugged brown plugged in and the bulb is bright. (all other wires unplugged)
Brown unplugged and bulb does not come on.
Voltage selector is set to 240v should be fine.
 
Unless there is something weird happening, like a modification to the mains wiring done by persons unknown, it does indeed look like the transformer is damaged.

As this is such an unfortunate possible outcome - I open this to the floor (always was), - does anyone else have any ideas?
 
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Hyperion said:
Unless there is something weird happening, like a modification to the mains wiring done by persons unknown, it does indeed look like the transformer is damaged.
Click to expand...

I wouldn't rule out anything at this point, but the transformer is looking like the culprit.

Hyperion said:
As this is such an unfortunate possible outcome - I open this to the floor (it always was) - does anyone else have any ideas?
Click to expand...

I will get a 100w bulb for the DBT, more to rule it out than anything else.
Well I did want a project. This is a chance I took when getting a non working amplifier, you have too loose sometime.
I still intend to get it working.
 
Not much doubt that the toroidal transformer is faulty.
Getting 0.0ohms on both the yellow and purple wires.

aHF5qoA4T2W0bfeeOSP44Q_thumb_4b.jpg

Just for fun these are the readings I got.

PT701
Yellow 01 0.0ohms + beep on meter
Yellow 03 0.0ohms + beep on meter

Purple 02 0.4ohms + beep on meter
Purple 04 0.8ohms + beep on meter

Blue x 3.7ohms
Blue y 3.7ohms

PT702
Orange 11 15.7ohms
Orange 12 15.4ohms

Yellow 01 4.1ohms
Yellow 02 3.9ohms
 
Man that really sucks.
Your thread has been a good read, and has produced great information.
I feel bad for you and wish the outcome was more positive.
Hope you find a power supply.
 
Oh dear, that really makes me angry, because it was caused by simple block-headed incompetence, you have to abuse a Sansui transformer very badly to cause that kind of damage.

Replacement transformers are not impossible to find, but you might have to wait a while.

I really feel for you and the disappointment you must be feeling.
 
Hyperion said:
Oh dear, that really makes me angry, because it was caused by simple block-headed incompetence, you have to abuse a Sansui transformer very badly to cause that kind of damage.
Click to expand...

She certainly has been through a tough time.

Hyperion said:
Replacement transformers are not impossible to find, but you might have to wait a while.
Click to expand...

I will certainly be keeping a lookout for a replacement just incase. I found a post from 2016 a while ago about an AU-20000 transformer, @miromustang helped a member get a new toroidal made for very reasonable price. I doubt that particular option is available now but it is just a case of finding someone who can make a new one or rewind the old one.

Honestly I was half convinced that the power supply is bad so that cushioned the blow once I found out for sure.
I'm only doing this for fun and to have a couple of nice amplifiers in the end (mission accomplished already with my 517 and 717).
I'm just imagining how satisfying it will be if I manage to eventually repair this 919.
 
DB-7 said:
Man that really sucks.
Your thread has been a good read, and has produced great information.
I feel bad for you and wish the outcome was more positive.
Hope you find a power supply.
Click to expand...

Thanks for your kind words.
Hopefully this thread will return triumphant sometime in the future,
 
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