** Hum on right channel - Sanyo 9990K

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jimmyjimmy19702010

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May 5, 2012
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Hi Guys,
View attachment 479

Picked up this unit last week and noticed have I the following issues:

* On tape mode with a tape running, a get a hum from the right channel that is controlled by the volume when on AC mode only. On DC, no hum at all.

* When turning the unit off, I get a single 'woop' sound from the right channel on AC mode only, no 'woop' on DC.

* Before cleaning the switches etc, I noticed if you turn the unit off, (AC or DC), you still get a hiss sound from speakers when turning up the volume like the unit is still running.

I thought maybe a micro switch on the deck was sticking causing the unit to still think the deck is operating. This issue has disappeared since I did a full tear down and clean yesterday. All switches, micro switches, recording bar and pots etc have been thoroughly cleaned and all now working 100%.

Otherwise, all functions on the unit are working fine and the sound output from both channels is equal and sounds very strong but the 'woop' and hum on AC tape mode issues still persist.

Any ideas?

James....
 
BoomboxLover48

BoomboxLover48

Member (SA)
Dec 3, 2010
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Chicago, IL
One channel only? In most cases they are due to bad contacts. I would clean the long record switch real good.

Do you see the same problem with line in and radio mode?

I would try a DC adaptor and confirm it.

If there is no hum when used the right DC adaptor, change the large electrolytic capacitor in the power stage near the large transformer.
 
Vintage Man

Vintage Man

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Apr 18, 2013
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gmail.com
jimmyjimmy19702010 said:
Hi Guys,
Sanyo M9990K 002.jpg

Picked up this unit last week and noticed have I the following issues:

* On tape mode with a tape running, a get a hum from the right channel that is controlled by the volume when on AC mode only. On DC, no hum at all.

* When turning the unit off, I get a single 'woop' sound from the right channel on AC mode only, no 'woop' on DC.

* Before cleaning the switches etc, I noticed if you turn the unit off, (AC or DC), you still get a hiss sound from speakers when turning up the volume like the unit is still running.

I thought maybe a micro switch on the deck was sticking causing the unit to still think the deck is operating. This issue has disappeared since I did a full tear down and clean yesterday. All switches, micro switches, recording bar and pots etc have been thoroughly cleaned and all now working 100%.

Otherwise, all functions on the unit are working fine and the sound output from both channels is equal and sounds very strong but the 'woop' and hum on AC tape mode issues still persist.

Any ideas?

James....
Click to expand...
DO YOU HAVE ANYTHING PLUGED IN TOO THE SAME OUTLET???
 
Vintage Man

Vintage Man

Member (SA)
Apr 18, 2013
401
0
16
60
OSHAWA ONTARIO CANADA
gmail.com
jimmyjimmy19702010 said:
Hi Guys,
Sanyo M9990K 002.jpg

Picked up this unit last week and noticed have I the following issues:

* On tape mode with a tape running, a get a hum from the right channel that is controlled by the volume when on AC mode only. On DC, no hum at all.

* When turning the unit off, I get a single 'woop' sound from the right channel on AC mode only, no 'woop' on DC.

* Before cleaning the switches etc, I noticed if you turn the unit off, (AC or DC), you still get a hiss sound from speakers when turning up the volume like the unit is still running.

I thought maybe a micro switch on the deck was sticking causing the unit to still think the deck is operating. This issue has disappeared since I did a full tear down and clean yesterday. All switches, micro switches, recording bar and pots etc have been thoroughly cleaned and all now working 100%.

Otherwise, all functions on the unit are working fine and the sound output from both channels is equal and sounds very strong but the 'woop' and hum on AC tape mode issues still persist.

Any ideas?

James....
Click to expand...
the switch that you have when you plug in the cord may be sticking,, can happen with age..... separates the ac dc mode.. could be sticking... spray the inlet lightly. and work the cord in and out. simple things like this make a tec go awwwwwwww... whats wrong..... just trying.... hope it all gets solved...
 
baddboybill

baddboybill

Member (SA)
Jul 14, 2009
11,092
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55
Hudson Florida
Most likely it's record bar. Try cleaning it. Also you can try pressing record switch a bunch of times to take care of issue for short term. Just hold record tab inside of deck and press record and stop a bunch of times. Then test tape ;-)
 
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