9090DB losing channel

Duke

Active Member
Hello all you Sansui's . . .

Just took delivery of a nice looking 9090DB and am beginning to test it.

At start -up the left channel is very weak and fades in and out.

It seems that especially at low volume the left channel is very, very weak, sometimes distorts and only after you increase the volume and let it warm up does the left channel become fully active then it at times it will fade again at low volume?

The right channel is perfect all the time.

The party I purchased it from said they had cleaned all the switches . . .

All thoughts & comments are greatly appreciated ?

:confused:
 
just a long shot-- but try fiddling (technical term there) around with the dolby noise reduction circuit and see if that effects your problematic channel.

I have read about some having issues with this db circuit.
I am sure someone with far more experience will show up and give you some help, but thats what I'd try first.

it's a good idea to contact the seller and tell them of your issues FIRST before doing trouble shooting or repairs.

Good luck,

partschanger technician Tal
 
First, I would test with a known good source like a CD or tape. Try several of the inputs; AUX, TAPE1 & 2 etc. to see if the problem is consistent.

Stay away from FM except to use it to set controls, volume levels etc. There are a couple of problems you could be adding into the mix if you use FM; first, just ignore the Dolby as it is a discontinued technology - there are no FM Dolby broadcasts to my knowledge. Second, your Muting circuits may not be working correctly.

I have found that with these Sansui's, you can have a channel working a low volumes due to switch contacts; specifically the SELECTOR switch, the VOLUME control (especially at the bottom end) and the TONE DEFEAT (or even the tone controls themselves).

Switching or rotating these quicky a dozen times can restore the weak channel. If it does *or* if you get significat static you have oxidized contacts or wipers and they need cleaning AND cycling after cleaning dozens (even hundreds) of times to clear them.

I have a G-8000 that still sometimes looses the left channel even after hundreds of cycles - it's the SELECTOR switch. It's hard to clean (very well hidden!!).

Paul
 
I've never looked at the construction of these switches, but after X amount of years, I'm starting to think they can wear out as well! My 2 cents.
 
Thanks !!!!!

Thanks for your replies . . .

Prior to purchasing the 9090DB, I did ask the seller (repair guy) what if anything was wrong with unit, I felt comfortable with his responses.

Regarding the left channel fading in & out - after reading your posts, I carefully switched the dolby switch several times, and it appears that this has resolved the problem - so at the moment the left channel sounds perfect . . .

I spoke with the seller and suggested that perhaps I clean the switches, he said he wouldn't until they get dirty, as he recently cleaned them.





:D :dunno:
 
I was getting similar problems with two of my AU-717's -- it may be a cold solder problem -- but it may also be an electrolitic-capacitor.

The electrolitic-capacitors have about a 20-year life span.

Replacng ALL of them will likely solve the problem -- it should be done sooner or later.

To be certain, my AU-717's are like NEW now! :D
 
The Dolby switch is the one that causes most of the problems. It is not as accessible as the selector switch, and most likely does not get cleaned as it should. You can try to remove the bottom of the unit and spray the switch with Deoxit D5 and then Deoxit pro gold. If you are lucky you will get the stuff on the this switch. What I do is remove the front panel the remove the metal bracket holding all the switches and controls and them clean them as above. It is a lot of work but it is worth it.

If the seller cleaned them with some other contact cleaner it usally won't last long. Try the deoxit. It seems to last for many many moons.

Also, I only use the Deoxit D5 not the Dn5, the D5 just seems to work better. (At least for me). The Dn5 is not flammable, the D5 is so use caution. Clean only when the unit is off.
 
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