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Sansui au-717 will not power on

R

Ryon

New Member
Good evening.
I have a Sansui au-717 and am wondering if someone would be able to guide me through troubleshooting why my au-717 will not power on. I had it powered on last week listening to it, and it shut off on its own. Now when I flip the switch to on, I do not see the red light blinking like I used to. I checked the fuse in back with an ohm meter and it tested good. Other then popping the cover, I have not dug too far into the amp. I am looking for some guidance to troubleshoot before I start pulling the boards out.

Thanks in advance!
-Ryon
 
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I was just recently scammed on an AU-717 here in Oz(sob)
Some lowlife called Jack Henson
Bsb:062948
Account num:16341154

Feel free to send those bank details to Nigeria.

Since I don 't have a AU-717 suppose the best I can do is work on one.
I'm not a tech so maybe best to wait for one.

Obvious place to start is power supply. Again, I'm not familiar with
the layout, just working from the service manual.

Power Supply Board F-2663
DC Voltage measurements, black probe connected to chassis or black
speaker post.
Pin 17 OR 19 (+33V)
Pin 23 or 25 (-33V)
Pin 18 or 20 (+33V)
Pin 24 or 26 (-33V)

Power Amp
Pin 12 (+56V)
Pin 4 (-56V)
 
From your description it seems like at least 2 of the 4 internal onboard 7 amp fuses have blown, or a lot less likely, you may have a faulty mains switch on the unit. If you are not experienced in electronics fault finding I feel this one will be best left to a tech to sort out.

Some things to check have been outlined above, good advice for a basic health check.

Unless anyone else has a better suggestion?
 
Last edited:
Thanks for the replies! I am assuming i will need to take all the boards out at the top to get to the bottom where those fuses are located?
 
Check the power switch. Be sure the contacts in it haven't fried. Do you have anything plugged into the "switched" outlet on the back of the amp?

- Pete
 
I had the record player and tuner connected to the outlets on the back. I dont recall which specific outlets either was connected to though. Is it best practice to not use those outlets?
Thanks
Ryon
 
LBPete said:
Do you have anything plugged into the "switched" outlet on the back of the amp?
Click to expand...
The question from LBPete is about whether the power switch is working ok, that is, AC Switched Outlet (for eg turntable) works normal
means the power switch is working OK.
 
mbz said:
The question from LBPete is about whether the power switch is working ok, that is, AC Switched Outlet (for eg turntable) works normal
means the power switch is working OK.
Click to expand...

I just tested it and the switched outlet works.
 
Ryon said:
I had the record player and tuner connected to the outlets on the back. I dont recall which specific outlets either was connected to though. Is it best practice to not use those outlets?
Thanks
Ryon
Click to expand...
There is no problem using those outlets for a turntable and tuner. That's what they are for. If you plug something like a toaster or stage lights into them, you will fry the power switch.

Although I wasn't thinking of it in my original post, as mbz pointed out, if the switched outlet turns on and off with the power switch, the switch is working and not the cause of the unit not powering up.

Please post the serial number for the database. Click on the link in my signature block.

- Pete
 
I found 2 blown fuses on the rear portion of the internal power circuit board. My hardware store had 7.5 and 6a fuses. I got both but tried the 6a fuse and both blew as soon as i turned the amp on. Looks like this isnt going to be a simple fix.

Im going to take readings this weekend of what mbz suggested. Any other tips or things to look out for? I have read about the glue being corrosive. Maybe that is shorting something out.

Ill keep you posted.
-Ryon
 
Blowing both fuses, not good. 1st, get that unit on a dim bulb tester before applying power again, once you have a current limiter remove the six connectors from each amplifier card (they just slide off and are color labeled for ease of re-assembly), replace the two fuses and apply power through the dim bulb tester. If the bulb stays bright turn off unit immediately, much deeper investigation needed. If the bulb goes dim I would suspect output transistors at the least. Let the forum know.
 
I'm in agreement with Overundr1, it's pointless to attempt to measure those power supply rails while your blowing fuses.
Like he said DBT and...
 
Reading through this thread I am finding it a bit odd that this AU-717 suddenly died, apparently without any prior indications of trouble. The fault would now appear to be quite a serious one in vintage amplifier terms, I'll be interested to see what the cause was, and what parts are needed to fix the issue.
 
I truly appreciate everyone's help! You guys are a great community and very quick to reply and help!! Thanks again, and I will post what I find out.
 
Errant thought, make sure the long ground bar visible between the bottom of the 4 big capacitors did not somehow touch the bottom cover. If it did those fuses will let go immediately as the power supply sees a dead short.
 
The ground bar is not touching the bottom.
I did the dbt using a 60w and the bulb did not dim. I waited about 3 seconds before cutting power. The dbt failed with both the right and left channels disconnected. I did not see any visual signs of burnt components. The red light is still not flashing either.

What do you recommend my next steps are?

Thanks
-Ryon
 
Hi Ryon,

If the dim bulb isn't dimming with the driver modules disconnected from the power supply, then it may be that you have a shorted rectifier diode in the power supply board. The 10D-2 diodes, D5 to D12, that supply the pre amp power supplies would be the first place I would look.

Cheers

John
 
I finally got to taking the amp apart. I did find 4 resistors that are corroded and oxidized due to the glue. I have not pulled the diodes yet to test, that will be another day as it is getting late...

-Ryon
 
Hey guys! It's been a while since I posted. Bringing this back up.... Can someone point me to a list of parts for this amp? It's been long enough and I'd love to get this thing working again!

Thanks!
 
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