Sansui AU-317 restoration project - 56k warning

[destroyer X]

into 4 ohms.... evaluating by the maximum power consumption (If real) it cannot... the maximum efficiency into Class AB use to be less than 65 percent.

So.... this means... 130 or 140 watts maximum usefull audio power (65 percent of the maximum consumption)...and this is left channel plus rigth channel...or 65 to 70 plus 70 watts maximum....of course this will be into 8 ohms loads.

And why so small?

I imagine the supply is not huge enougth... the Dc voltage is falling down in a big ammount....so.... not to change the supply, some help can be big condensers, as they load enormous quantity of electrons and will supply them when the supply DC voltage fell down because of consumption.... the average voltage during hard use will be sligtly bigger, and the peaks or power will also be bigger...this means more dinamics and better power into 4 ohms.

Also old rectifiers... i love to put more in parallel....under the board.. a lot of 1N4007 in parallel... they are lovely, small and each one of them can hold one ampere...very nice folks..very cheap ones.

If they had used decent transformers, this same amplifier could produce 120 watts each channel, both channels driving, continuous and over 4 ohms speakers.... the consumption, in that case would be something more than 450 watts.

Under specified, this may result in nice dinamics into 8 ohms with interesting decay of power....interesting effect... i like it.

regards,

Carlos

[Nordic]

Hi Carlos if you look at specs on service manual cover you will see it is not rated for 4 ohms at all.

Only other relavent rateing on there says.
Max consumption 365W
Rated consumption 215W (265VA)

Weight 9.7kg (21.4lbs)

Saw the one channel has 241mV offset, lets hope it is just drift.
Other cahnnel at more respectable 30mV.

Offset is adjusted via 4 trimpots, 2 for rough setting, 2 for fine adjustment.

These boards are realy a work of art in places... Found very interesting, almost no ground traces... they would wire all the the groundbus, with wires. The traces are beautifully drawn by hand... realy arty in a zen way.

[destroyer X]

The bias was drift.... also the trimpot... put a dot into the trimpot

and other dot of alignment around, as reference to return the trimpot to almost the same previous position.... and turn it many times from maximum to minimum and opposite.... i use WD40 while doing that... it is good to remove dust, oxide and to check the trimpot..if bad...you will see this fast... and better to discover that before sniff smoke.

You will be able to zero the offset.... and it will have drift because heat.... but...better not to give another touch.... adjust it almost cold after 2 minutes of warm up.....

You will see that we do not perceive small offset differences...but bias differences are easy to perceive.

Have you watched thread...our threads about Dx?.... the Speaker Sansuí...hehehe...sounding very nice..... i like it.

To clean your panel the WD also works....but..... have to be removed with a dry cloth...as if stay too much long my melt the white printed names you have over your panel.... test it in advance.... a little bit oiled and polished turns beautifull.

Have to apply and remove, it is able to remove dirty, but has to be removed...not entirelly removed, just a very thing surface will remain that will dry after a couple of days.

Also too much friction with cloth produces static that attracts dust into it too...so..... is able to make it pretty, but not for too much long as dust will "land" into your panel.

Using some times each month things goes fine.... easier to remove dust with a soft brush after cleaning this way...also finger prints will disappear... pieces of cake, biscuit and so on..ahahahah

WD40 and turning potentiometer many times use to remove almost all noises from the unit.

regards,

Carlos

[zeonrider]

Nordic, don't use WD40 it is not for electronic.

Eating cooper.Better way is some contact cleaner, and the best way is to change bias trimpot.

For front use hot watter & dish soap, good result.

I, don't belave only 3 of us tolking about old Sansui.

Regards zeoN_Rider

[Nordic]

Thanks for the practical advice

[zeonrider]

I, see service manual is helpful, go my son,go!

Regards zeoN_Rider

[Nordic]

Offset was easy to adjust, and is pretty stable...

I am scared of touching the bias pots though...

The service manual says it should be adjusted until 10mV between probe points indicated... but it seems to currently be at 25mV give or take a fraction on either channel... I find it odd that 2 pots would drift so far yet stay so close to each other...

Do you think it is possible the factory adjusted this to 25mV?

[destroyer X]

Dear Nordic... Let's put Dx Speaker to play together your Sansui.

Dx Speaker is Sansui too.

regards,

Carlos

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Dear Zeon

I am using WD40 since the sixties... never melt nothing important...uoops!.... i use it to detach those adhesive hard to remove...contact glue.

hehehe.

Maybe Zeón WD had some nuclear power..ahahahaha!

never mind..take your WD and i will take mine.

regards,

Carlos

[zeonrider]

If it's a WD40 war you want, a WD40 war you get.

Ha , Ha , Ha .

The force is strong in your WD40.


Regards zeoN_Rider

[destroyer X]

Also hot to make love...temperature is good to do nothing

ahahahahah!

regards,

Carlos