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Sansui 317 High Volume, Dancing DC Offset after click, A bit not centered.

R

ReisDaddy

Active Member
Hello guys, i've been infected by Sansui virus. Now i buy another Sansui 317 after long waiting because its getting harder to find. Plan to buy 5900 but its far more worst, mostly many rust on the back panel.. Then suddenly Sansui 317 show up, then i gofor it. As usual when it arrived, check dc offset, bias. All is done. Then when i play the music, just with 1 click of volume knob rotation, it sounds like a volume of my another amplifier that the volume is around 8-9 oclock. Then i heard a view pops, im rushing to shutdown the amp.
Then i check dc offset, just after relay click, it jump and dancing around 0.2v down to 0.1v then to 0v. In just a view seconds. It is scary right?

I saw a view replaced transistor that does not the original number as in schematic.
Then i did recap and replace all the ecaps except the big reservoir capacitor, and also transistor as in AKers recommend (below is the table that i replace). Also my Sansui 317 has no fuse resistor. After recap done, i did test again, and the volume is a bit better, but still loud. No more pops or crackling. Now the volume knob just 2 clicks from 0 is already loud like the level of casual listening volume. Its around 60-62db. When i check online in a view youtube video, mostly the volume knob is higher than 9 oclock, its like 10 maybe 11 oclock.
The offset still dancing around 0.2vdc after relay click. And the balance is abit to the right, not really centered.

I did check the volume pot visually not replaced yet, still original.


Here is board F-2752 Control Amp transistor table
PCB NUMBERSMPhysical (When i get)Replaced
TR012SA872 D, EA999 ?KSA992
TR02 2SA872 D, E No markingKSA992
TR032SA906 G,H A906KSA992
TR042SA906 G,H No markingKSA992
TR052SA906 G,H A999 ?KSA992
TR062SA906 G,H A906KSA992
TR072SC1775 E,FC1775no
TR082SC1775 E,F C1775 no

Any idea from where to start checking ?

I did check roughly after recap, the main voltage after big mylar caps (in my sansui it is in the back of pcb/solder side)
C902 is around 40.5 vdc
C901: 40.46 vdc.
And another power line for relay after C601: 22.13v and 0.006vdc.

Any help would be appreciated.
 
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HIGH VOLUME UPDATE:

I found the problem. I read in a view thread and forum that newer DAC is higher output that older amp input is lower volt. That is why we get high volume or high gain in the amplifier. My source is DAC, Topping E30ii which is in the spec output 2.1vrms while the Sansui 317 in service manual say Input AUX: 150mv.
And found this thread: https://audiokarma.org/forums/index.php?threads/sansui-au-317-gain-issue.903607/
The solution is using voltage divider. @Al Casey help me about the divider.
Also found in :
https://forums.stevehoffman.tv/threads/make-your-own-attenuator-cable.899602/
I did try R1 56K and R2 22K, im not sure, i feel the result is not something im happy with, i feel different, like its more harsh? Maybe its just my placebo effect?
I will leave them as what it is without voltage divider.

UNBALANCE UPDATE:
Contact cleaner solved the problem. I think one of the switch or pot that must be cleaned.

And this Sansui 317 is amazing! Time to clean them and put back all the cover and faceplate.
Hope this help to other AK users.
 
ReisDaddy said:
I did try R1 56K and R2 22K, im not sure, i feel the result is not something im happy with, i feel different, like its more harsh? Maybe its just my placebo effect?
Click to expand...
If it sounds harsh, blame it on the resistors. If you are satisfied with the attenuation, upgrade the resistors, they are in the signal path.
 
HIGH VOLUME/GAIN UPDATE:
Now i understand, after reading more, in that time there is no CD, no DAC, and highest output for home use around 1v. So i imitate like my Nakamichi LX-3 output is 1v.
I use Dale CCF55. R1 = 7.5K, R2 = 6.34K = +- 0.962v
And the result 5 clicks is equal gain to 2 clicks without divider.

Very nice sounding amp... musical! Im very happy with the result. I think now its my best amp in my chain.
Im curious to my next target : Sansui AU-5900
 
I had a problem with a Sansui AU-717 starting at high volume with the knob turned all the way counter clockwise. The problem in my case was that one of the flying leads between the tone PCB and the Alps volume pot had broken off. So there was no ground to pull down the attenuator.

If you still hear audio with the volume turned all the way down you could check to make sure none of the wires are disconnected. Then again I don’t know if the 317 has flying leads connecting the volume pot.
 
ReisDaddy said:
Very nice sounding amp... musical! Im very happy with the result. I think now its my best amp in my chain.
Im curious to my next target : Sansui AU-5900
Click to expand...
Congrats.
To add to the impressive resource and advices promulgated by the experts on this forum, here's an article that applies not only to the venerable AU-317 but also to audio gears in general.

...and there are the inspiring words of wisdom by @Hyperion
Have fun with your projects!
 
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