Sansui Au7900 or G7700 ?

[Eros69]

Hi Guys

Hi all My first post here seeing as i am now a sansui addict and casualty, I have recently purchased a sansui AU7900 which i have had restored by a sound Professor which works fine i have it connected to a pair or celestion ditton 44s and a apair of celestion ditton 33s, I love thsi amo but it has always seemed a little lacking in the bass department.
2 days ago i came across a sansui g7700 which has 120 w per channel while the au7900 is lots less in comparrison i havent collected the G7700 yet and well just after your thoughts as to which will be better i iwll take it for full restoration if need be.

any input welcome

Thanks

Richard

 

[Sriskie]

I had both and to me the AU-7900 is the hands down the keeper. The G-7700 is good...and pretty, but the AU-7900 is something special.

 

[tarior]

G-7700 is a great sounding receiver, very clean, good power. Be aware that it will need to be restored. The bias string is a ticking bomb, not tough to fix, but the tech needs to know what he is doing. The heatsink compound Sansui used on the output transistors in those also has a serious tendency to completely dry out.

 

[Eros69]

I had both and to me the AU-7900 is the hands down the keeper. The G-7700 is good...and pretty, but the AU-7900 is something special.

Hi Sriskie well while i was writing the post the g7700 arrived so i went to collect it .. the g7700 took me a while to work out how to rig it up, but the bass is incredible compared to the au7900 and also sounds much better, the treble just flutters away and sounds incredible.. thats before a proper test... as i had to hide it from the wife before she got home and found me with it ..... she will kill me when she knows i have bought it for sure so if i dont write back you know to send a search party out for me.
But for 150 pounds i could not say no
.
The lamps on the tuner section dont work and the quartz lock part too presume thats the chip thats gone faulty but we will see will take it to my professor guy.
The other lamps work fine

Considering shes never been worked on im very very impressed with the sound she makes so far.well i havent looked inside as i normally break things when i try to be clever and get roasted by the professor.

Although i must admit i did have my speakers wired up wrong to the au7900 which i have now rectified.. even so the bass is not there no punch at all compared to the g7700...






Couple of pics attached for your viewing

 

[SoCal Sam]

AU-7900 is the winner. Successive Sansui receivers suffered from cost cutting culminating in the G-x700 series. They do not sound bad but when compared to the previous year's G-x000, the cheapness is apparent.

 

[tarior]

If the quartz lock isn't working, the first thing to do is thoroughly clean the tuning capacitor and lube the contact points in it with either Deoxit Gold or F100. Second thing (or first, both need to be done) is check the points where the tuning capacitor is soldered to the board for cracked solder joints. Even a barely visible crack will mess with the tuner function.

DO NOT TOUCH, or even breathe on, the bias trimmers.

 

[Eros69]

If the quartz lock isn't working, the first thing to do is thoroughly clean the tuning capacitor and lube the contact points in it with either Deoxit Gold or F100. Second thing (or first, both need to be done) is check the points where the tuning capacitor is soldered to the board for cracked solder joints. Even a barely visible crack will mess with the tuner function.

DO NOT TOUCH, or even breathe on, the bias trimmers.

Ok but there aint no way i would dare to start doing that will show the professor guy your recomendations

Thankyou !!

 

[spark1]

Yes...bias problems can be very difficult to deal with - I've been trying to find help with one just recently.

If the 7900 has been restored and doesn't outperform the 7700, I would say that something wrong was done in the rebuild of the 7900.

The power difference between the two is not very significant. But if you like the 7700 more than the 7900, then you don't need to ask which one is better!

 

[Eros69]

Hi Well
Took the lid off the beast just to have a look inside pictures below its very very dirty and a few fried things in there i reckon, i dont even think the power supply is original looking at other G7700s on the net compared to this one.

Yep the power transformer is definatley not the original one can see the clean area where the old one was removed damn
Also when the stereo mode button is on stereo only plays on left hand channel
Press mono and it plays on both.

Not sure how much this will cost or even if it will be possible to restore

How someone can let such a machine get in such condition is beyond me

 

[tarior]

That is some ugly work in there. Just think how great it will sound when it is functioning properly.

 

[Eros69]

That is some ugly work in there. Just think how great it will sound when it is functioning properly.

What i dont get is how this thing actually powers up and works in the condtion its in ....unbelievable

will take it to my professor guy but been looking all over for a replacement psu transformer cant understand which part number it is as there seems to be 2 different ones for the g7700 looking all over the web at pictures one part number is 4003090 and the other is 4003092. rare as unicorn poo by the looks of it ..not going to be easy to find

 

[Zekeman]

I have never heard a 7900 lacking in the bass dept....you must be more of a bass freak than I am.

 

[tarior]

What i dont get is how this thing actually powers up and works in the condtion its in ....unbelievable

will take it to my professor guy but been looking all over for a replacement psu transformer cant understand which part number it is as there seems to be 2 different ones for the g7700 looking all over the web at pictures one part number is 4003090 and the other is 4003092. rare as unicorn poo by the looks of it ..not going to be easy to find

He definitely has his work cut out for him. If the present transformer has the proper secondary voltages, within 10% of the values noted in the service manual (you need one) I would leave it be for now and concentrate upon everything else. Save a search on ebay for the correct transformer. One will turn up eventually.

 

[Eros69]

I have never heard a 7900 lacking in the bass dept....you must be more of a bass freak than I am.

Hi maybe i have the filters wrong or something the bass is there but there is just no punch to it and its not deep at all..
sstrange thats why i saw the g7700 and bought it ..

 

[ghazzer]

This G-7700 has definitely been "rode hard and put away wet"!

It has the later version of the Digital Display board (F-3220 vs F-3000) so it may be a "newer" G-7700, and not conform to all the schematics & P/Ns in the SM. Please post the S/N of this G-7700 and pics showing the inside and outside heat sinks.

See Dcook154's thread about some of the differences:
http://www.audiokarma.org/forums/index.php?threads/sansui-g-7700.808272/

As Tarior mentioned, these F-2980 bds have a hair trigger. The four single turn 100Ω trimmer pots should be replaced before doing any other work on this bd - make sure you read up on the precautions.

 

[Eros69]

He definitely has his work cut out for him. If the present transformer has the proper secondary voltages, within 10% of the values noted in the service manual (you need one) I would leave it be for now and concentrate upon everything else. Save a search on ebay for the correct transformer. One will turn up eventually.

Thanks Tarior yes that sounds like a plan will keep you updated...

 

[Eros69]

This G-7700 has definitely been "rode hard and put away wet"!

It has the later version of the Digital Display board (F-3220 vs F-3000) so it may be a "newer" G-7700, and not conform to all the schematics & P/Ns in the SM. Please post the S/N of this G-7700 and pics showing the inside and outside heat sinks.

See Dcook154's thread about some of the differences:
http://www.audiokarma.org/forums/index.php?threads/sansui-g-7700.808272/

As Tarior mentioned, these F-2980 bds have a hair trigger. The four single turn 100Ω trimmer pots should be replaced before doing any other work on this bd - make sure you read up on the precautions.

Hi the serial number is 81003070722 will post pictures tommrow as the wife came home and i had to hide it fast...
I presume that was made 1980 or 81 ? month 3 ?

thanks for the link too

 

[Eros69]

Hi the serial number is 81003070722 will post pictures tommrow as the wife came home and i had to hide it fast...
I presume that was made 1980 or 81 ? month 3 ?

thanks for the link too

And this beast aint easy to hide .. even under all my fishing equipment very hard work

 

[spark1]

Might be easier to figure out what's wrong with the 7900...by your description, something is definitely not right with it.

 

[Eros69]

Might be easier to figure out what's wrong with the 7900...by your description, something is definitely not right with it.

Hi Actually have some graph readings taht were performed by a machine after he restored it can post them later will find them out he restored everything back to how it left the factory.. doesnt like to modify and change thing unless absolutley no choice..