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Sansui AU-6900 Questions and problems
Sansui AU-6900 Questions and problems
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Old 31st August 2011, 08:37 PM   #1
josping is offline josping  Spain
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Default Sansui AU-6900 Questions and problems

Hello everyone, I'm from Spain, and I rescued from the trash a Sansui Au-6900, I stimate was not used in the past 20 years. when i power it up the light comes on in the front but nothing, no sound or anything, someone can tell me if today can repair this amplifier?
Another question I have is that the back comes with a red label in the connections "Pre Out, Main In" that says exactly.
"IMPORTANT, do not insert these pin plugs into jacks other tan PHONO. inserting them into certain jacks will cut sound off"
it curious that two pin plugs were coming in those two connections inserted "pre out, main in" do I can take or leave?, must be inserted somewhere specific?
What usefulness have they these pin plugs?
And last question: Over the connectors "Pre Out, Main In" is a switch that says "PRE-MAIN" and has two positions "separated and connected" in that position should be set?
thank you very much everyone.
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Old 1st September 2011, 12:19 PM   #2
sregor is offline sregor  United States
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The red tage and the shorting pins should be at the phono inputs only. They will cause no output if put in the pre-main jacks. The switch is normally in the connected position - it is for using an external amp with the 6900 acting as preamp, or to use a different preamp with the amp section of the 6900, or for connecting up crossover and amplifier(s) for biamping speakers. As an aside - sometimes dirt or corrosion on that switch can cause intermittent problems, but not usually no output. IMO it is a very nice midrange amplifier. Hope you get it working.
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Old 1st September 2011, 08:40 PM   #3
east electronics is offline east electronics  Greece
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also placing the "short circuit" plugs to any tape out will also mute the amplifier ...correct said these are only to be used in the phono inputs only if these are not used by actuall phono system .

Your amplifier will need restoring eventhough might have not been on duty for very long time its a fact that al elctrolyticapacitors inside are not working any more ...

kind regards sakis
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Old 1st September 2011, 09:30 PM   #4
DigitalJunkie is offline DigitalJunkie  United States
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It should be a good amp,worth fixing up,IMO.
I have an (original) AU-7900 that I've been using for years,it's a great amp. One of these days I'll get around to putting some new caps in it.
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Old 1st September 2011, 09:37 PM   #5
firechief is offline firechief  United States
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Take a picture of the front with it turned on, post the picture. Connect speakers, put your ear right next to the speaker, and turn on the power. Do you hear anything? Turn on thump or hiss? Get back to us.
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Old 2nd September 2011, 01:29 AM   #6
josping is offline josping  Spain
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Hello, thank you very much for all the responses have been helpful. This amp I rescued from the trash for 4 years ago, with another amp, a Marantz model 1090 and 4 speakers Marantz HD550. The Marantz work from the first day, only use a dielectric cleaner, to clean the controls because they made some noise when using some controls, but the Sansui never worked, but of course, had the "short circuit" pin plugs placed in pre-main, anyway yesterday I tried them out and still no sound.
As I did not know what else to try I came up with two RCA cables plug "pre out" on Sansui amp with "main in" in the Marantz. input source in the Sansui and speakers on Marantz and passes the sound to the speakers but I did not expect is that the volume control that worked was the Sansui and not the Marantz. Anyway, the tone controls, filters and loudness in the Sansui did not work but the Marantz, nor.
Having done this test with the switch "PRE-MAIN" in a "separated" position i heard a little "thump" on the speakers and turn off too. But if I change the switch to "connected" position, within 2 seconds of power on the amplifier, starts making a loud noise in the speakers force you to shut down the amplifier instantly.
I wanted to tell you something else is very rare and donīt know if I'm going crazy. when I made this connection when you turn on the amp did not hear the sound of the source that had connected it was a sound "no noise" was is like a sound test, several recurring melodies. Is this possible?

Another thing to ask, forgive me if I'm annoying, I'm looking online and seen several photographs like this, why would you put those bridges in the pre-main connections.Click the image to open in full size.

Last edited by josping; 2nd September 2011 at 01:45 AM.
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