Sansui 9090db

stereo1165

New Member
I posted something earlier today about this problem but not onn the Sansui thread.

I had this receiver given to me. Had no power. I know some but not alot about working on amps and receivers. Speakers are something I love to work on and refurbish.

A I said it did not power up. I check this site and first thing I did was clean all switches pots. When I took the top cover off there is 5 fuses.
4 are ceramic 10 amp 250volt fuses, I put all new ceramic 10 amp 250volt fuse in. The other was a clear buss 10amp 250v fuse also replaced.
I took the bottom cover and there was 2, 7amp 125v fuses. One blown one good. The wire through the middle was wider then normal which i am guessing is a slow burn fuse. The problem I have is everywhere I check radio shack and elsewhere did not have 7amp 125v fuses. All that I could find was 7amp 250v fuses. Question can I use 7amp 250v inplace of 7amp 125v fuses. I haven't fired up the receiver yet and won't until I know what to do about fuse.

Also I live near South Bend iIndiana. If the fuse isn't the issue I would like to find a Tech that works on vintage equipment. Willing to go 2+hrs drive over shipping.
 
Put the 7amp 250v fuses in. I turned the power. Every thing came on and safety turned green. So turned it off connected speakers and put CD into ax. Turned power on volume down speaker selector off. As soon as I turned selector switch to A a loud buzz came through speakers no music. I smelled something and thought it was the receiver. I shut it off and reconnected the speakers to my other receiver. The smell wasn't the receiver it was the drivers in my speakers. Fried 1 tweeter and 3 woofers. The 9090db stillcomes on and protection light goes green.
 
Check the amps Offset.
If the relay is engaging you could take the offset readings from the speaker terminals. Or is frozen closed.
To many coincidences to discount the receiver.
You want to see if any voltage is coming out of the set. Set your DMM to DC volts and put one probe on the Negative (Black) speaker terminal and the other on the Positive (Red) terminal. with the set turned on: Read the voltage. Do both right and left channels. make sure you have the A channel selected and probe the "A" speaker terminals. You might expect 50 some volts. 50 plus volts is bad, zero or near zero is good.
Scenario: The current welded the protection relay contacts and sent the railed amps voltage to the speakers.
Sorry for your losses.
 
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Check the amps Offset.
If the relay is engaging you could take the offset readings from the speaker terminals. Or is frozen closed.
To many coincidences to discount the receiver.
You want to see if any voltage is coming out of the set. Set your DMM to DC volts and put one probe on the Negative (Black) speaker terminal and the other on the Positive (Red) terminal. with the set turned on: Read the voltage. Do both right and left channels. make sure you have the A channel selected and probe the "A" speaker terminals. You might expect 50 some volts. 50 plus volts is bad, zero or near zero is good.
Scenario: The current welded the protection relay contacts and sent the railed amps voltage to the speakers.
Sorry for your losses.

Thanks. Will check that today. With receivers i know very little about them other then cleaning switches and pots. This a one i deffintly want to get up and running. I am trying to locate someone that does repiar but having no luck. Im within 2hrs of indy and chicago so hoping i can locate someone i prefer not to ship.
 
Zebulon, you are a glutton for punishment, three at once egads.
Wise old owl once said one never wires up speakers to a new piece of gear without first checking offset, been many many instances of speakers damaged by high DC readings.
-Lee
 
The fuses you found under the bottom cover, are they on the protection board next to a relay? Those fuses are in the audio output circuit. They should be the fastest fuses you can find. If one was blown, either the output was shorted or there is a fault with the audio output. Does the indicator on the front panel turn from red to green when you turn the unit on? Does it stay green?

- Pete
 
The fuses you found under the bottom cover, are they on the protection board next to a relay? Those fuses are in the audio output circuit. They should be the fastest fuses you can find. If one was blown, either the output was shorted or there is a fault with the audio output. Does the indicator on the front panel turn from red to green when you turn the unit on? Does it stay green?

- Pete
Once i changed the fuses and did turn it on the protection light flashed red then green and stayes green. But when i hooked up speakers all i got was buzz and fried my speakers. The receiver still powers up as should.
 
Thanks. Will check that today. With receivers i know very little about them other then cleaning switches and pots. This a one i deffintly want to get up and running. I am trying to locate someone that does repiar but having no luck. Im within 2hrs of indy and chicago so hoping i can locate someone i prefer not to ship.

Ok. Hooked meter up today. Connected to right side speaker terminal first. Put meter to DC and turned speaker selector to A with power on. Protection light flashed red then steady green. Right side measured 18.5 no more left side speaker terminal went to as high as 135.
 
I assume that is in mv. 135mv is just under the protection circuit threshold. Need to get a copy of the service manual, a dim bulb tester and adjust both values to zero dc. DO NOT turn the wrong adjusters, take pictures and ask first if you are not sure, turning the wrong adjusters can and will cause mayhem.
 
Check the amps Offset.
If the relay is engaging you could take the offset readings from the speaker terminals. Or is frozen closed.
To many coincidences to discount the receiver.
You want to see if any voltage is coming out of the set. Set your DMM to DC volts and put one probe on the Negative (Black) speaker terminal and the other on the Positive (Red) terminal. with the set turned on: Read the voltage. Do both right and left channels. make sure you have the A channel selected and probe the "A" speaker terminals. You might expect 50 some volts. 50 plus volts is bad, zero or near zero is good.
Scenario: The current welded the protection relay contacts and sent the railed amps voltage to the speakers.
Sorry for your losses.

Posted response earlier. Had meter set wrong. Checked again. Both showed negative 60.5. The protection light still flashin red then steady green.

Thank to all for input.
Vic...
 
I assume that is in mv. 135mv is just under the protection circuit threshold. Need to get a copy of the service manual, a dim bulb tester and adjust both values to zero dc. DO NOT turn the wrong adjusters, take pictures and ask first if you are not sure, turning the wrong adjusters can and will cause mayhem.

Yes it was mv. Will deffintly get service manual. And will be asking many more questions. Im not much on electrical but quick learner. Im looking forward to getting this up and . Thanks for all the info really appreciate it.

Vic.
 
-60.5 milivolts or volts? If it's 60 volts, you have big trouble. Do the same test with the meter set to AC volts.

- Pete
 
-60.5 milivolts or volts? If it's 60 volts, you have big trouble. Do the same test with the meter set to AC volts.

- Pete
Checked both again.
AC- Right and Left 19.7 milivolts
DC- Right and Left negative -62.5 volts

Thanks
Vic
 
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I'm very confused here. Are you taking these readings at the speaker terminals? You are saying it's putting out 60 VOLTS and it's not in protection, Green LED on the front panel? Something is very wrong here. Where exactly are you taking these measurements?

- Pete
 
I'm very confused here. Are you taking these readings at the speaker terminals? You are saying it's putting out 60 VOLTS and it's not in protection, Green LED on the front panel? Something is very wrong here. Where exactly are you taking these measurements?

- Pete
Its reading negative 60 at the speaker terminals. And when i turn it on it flashes red then steady green.
 
Something is very wrong here. Take the bottom cover off and measure the voltage on the blue and the gray wires that come off the bottom of the power supply board. That's the output signal from the driver board to the protection board.

- Pete
 
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