• The move to the new server is done. There are some software and database maintenance updates in process. This has us passing the hat around to help out. We appreciate any donations. Seriously, even a dollar helps. The payment page may be found here - https://www.audiokarma.org/support.html

Sansui AU-717 dead channel

blankenship

blankenship

New Member
My lovely AU-717 has been in (climate controlled) storage for awhile.
I hooked it up the other day, and seemed to work fine—but with a scratchy balance pot.

But as of yesterday, the amp is only amplifying the right channel—There is NO output from the left channel.
I replaced the 4 fuses, but no improvement.
Meanwhile, the scratchiness in the balance pot seems to have gone away.

Help?
 
Register to hide this ad
Try operating the 'connected-separated' switch on the rear panel a few times, make SURE you do this with the amp powered OFF.

These switches are absolutely notorious for causing issues like this - if this is the cause of the problem, as a follow up, a good squirt of proper switch cleaner (like DeOxit) will improve things greatly.
 
Last edited:
If that doesn't work, tap on the speaker relay with a Bic pen or other non conductive probe. If the channel comes back, the relay has to be replaced.
 
Thanks for the suggestions. No luck so far.
  • Turned the amp of, switched the 'connected-separated' switch back and forth a few times, and then turned amp back on. No change. Repeated the process—still no change. :(
  • Took the top and bottom covers off, tapped the speaker relay (the part that looks like this) a number of times from different angles while the amp was on. No change. :(
Other ideas?
 
If you have a couple of RCA phono cables you could try setting the amp to 'separated' and use the RCA cables to jumper the connections between 'pre-amp out' and 'power amp in'. Try this with 'right' to 'right' & 'left' to 'left' first - your results should be the same - no left channel. Now swap them, 'right' going to 'left' & 'left' going to 'right' - probably ok to leave the amp on while you do this but make SURE you have the volume at zero before each switch move or cable move.

If the 'good channel' changes sides then there is something amiss in the left channel pre-amp, if it doesn't change, the left power amp has a problem of some kind, (could still be the speaker relay).
 
When I set to "separated," do I choose the "direct coupled", or "capacitor coupled" option? Or does it make a difference?

Hyperion said:
If you have a couple of RCA phono cables you could try setting the amp to 'separated' and use the RCA cables to jumper the connections
Click to expand...
 
There is a switch setting which is simply 'separated' not direct coupled OR capacitor coupled.
 
Hey John- That's not what I see. It's a 3-position switch...There's a "Connected" position, and (2) "Separated" positions—"Direct Coupled" and "Capacitor Coupled". (Both of the coupled positions are fall under the "Separated" category). See photo
AUTU717-AUr.jpg
 
Sorry, you are correct - either of the separated positions is fine, of the two - chose 'capacitor coupled' for now. ;)

It's been a while since I played with my AU-717. :)
 
Hyperion said:
If you have a couple of RCA phono cables you could try setting the amp to 'separated' and use the RCA cables to jumper the connections between 'pre-amp out' and 'power amp in'. Try this with 'right' to 'right' & 'left' to 'left' first - your results should be the same - no left channel.
Click to expand...
Yes, this is what happened.

Hyperion said:
Now swap them, 'right' going to 'left' & 'left' going to 'right'...If the 'good channel' changes sides then there is something amiss in the left channel pre-amp, if it doesn't change, the left power amp has a problem of some kind, (could still be the speaker relay).
Click to expand...
When I swapped left-to-right, the good channel changed sides. Sound only coming from left speaker now.

Hm. Now what?
No chance that it's the Balance Pot? Any time I turn it to the left, I lose sound.
 
It is possible - but from here it needs an experienced tech to get in there and find out exactly what is wrong - not a job for a novice I am afraid to say.

Of the four main sections of the amplifier, you have now eliminated three sections, we can also say that the power supply is good (the fifth section ;)).
 
My guess is that it could still be a power supply problem - the power supplies to the pre amp and equaliser sections. I have repaired several 717's with a dropped channel due to the capacitor glue causing component damage (10k resistors) on the power supply board.

This can be easily checked if you have a multimeter.

Cheers

John
 
What dr*audio said... I had the exact same problem with one of my AU-717's and both of my AU-517's. In one case, it was the balance control needing to be cleaned. In the other two cases, it was because of buildup on the speaker selector switch. All three amps had been sitting unused for quite awhile before I picked them up. A good deoxit-ing brought them all back to perfect operational order. Also had this happening with a couple other amps I picked up and have since sold - in both cases, one channel not working, cleaning the controls did the job.

The other thing you can try is using a source with a stronger signal like a CD player, putting the balance to the soundless side, and pushing some good volume on that one channel - sometimes there can be relays that get stuck closed when the amp hasn't been used in awhile, and a stronger signal will eventually get them to pop open. Just make sure you're using speakers that can handle the burst when the relay pops open and you start getting full sound on that channel. Or a pair of speakers you don't care about blowing :)
 
I know this is a super long dead thread but I have to say how helpful it was to me today. It came up on my first google. I had the exact same thing: I pulled my restored AU-710 from temperature controlled storage and one channel (left) very very faint, then nothing at all. Hyperion's advice regarding exercising the 'connected-separated' switch worked like a charm.

Thanks!
 
The main problem with my 717 was the fuse resistors, 5 of mine were Open and several more were way out of spec. After changing them it worked great, put a meter on them I am sure you will find one or more open, the glue is also a big issue with corroding the legs off resistors and other parts

Equalizer board f2723 has r-47,48,49,50 82ohm 1/4w.
Tone board f2720 has r-37,38,39,40 82 ohm 1/4w.
Driver board f-2721,2722 r23,25 on each board and one or two on the power supply board. I will see if I can locate them.

replace them all with 1/2w metal film.
 
Last edited:
You must log in or register to reply here.
Back
Top Bottom