Sharp GF-9494 sound issue

[devol-toni]

I just bought Sharp GF-9494 and it's beautiful machine. Its look very good and it has very little sign of use.
But, it has problem with the sound. More specifically, when I press the on/off button the sound start with almost normal intensity on both speakers then after 2 seconds the sound starts to decrease on very low on both channels (same on the phone output).
The left channel sounds like that have only highs and the right channel sounds despite low sound plus with crackling.
I've already opened it and noticed that all the sliders are clean and like new, they glide very smoothly, and I think that they are not the reason for this issue.
The boombox has normal output signal from both sides via the line-outs.
Also the sound changes when i move the switch and activate the lights for VU and radio scale.

I searched in the base for such case but I have not found anything similar.

Any help will appreciated.

 

[Fatdog]

Try cleaning / working the internal record switch. It causes sound issues - mainly humming and squealing - but, it might be causing your sound problems too. That would be my first place to look.

 

[baddboybill]

I would try cleaning with deoxit or contact cleaner all switches especially power, bands and function switch and work them. Give us outcome afterwards


Bad Boy Bill

 

[devol-toni]

Thanks for advice guys, I'll do this.

 

[devol-toni]

I cleaned every switch and record switch with deoxit and still nothing changed.
I've thinking about something, since that the sound goes down after 2 seconds after switching on,
is it possible that some capacitors is bad on the amp section ?

If someone can help with this I'll appreciate


P.S. I used baddboybill's switch solution for deoxit the switches
http://www.boomboxery.com/forum/viewtopic.php?f=4&t=15793

 

[Fatdog]

Hmm, maybe failing / dying capacitor or maybe a resistor overheating?

 

[tshorba]

is it the same on batteries and mains power?

 

[devol-toni]

I have no batteries to check but I was try by DC input with 15 V supply and it is same.
I also measured internal transformer output and it shows right voltage -15 volts.

 

[baddboybill]

Have you tried using headphones. Maybe headphone jack is dirty/rusty and not making good contact...


Bad Boy Bill

 

[tshorba]

I would check cap C140 (4.7uf) it's on the DC side of the PS.

 

[devol-toni]

Have you tried using headphones. Maybe headphone jack is dirty/rusty and not making good contact...


Bad Boy Bill

Yes, since the box is already disassembled I only can heard the sound through headphones.

 

[tshorba]

Check your personal email, schematic sent to the address you supplied me

 

[devol-toni]

I would check cap C140 (4.7uf) it's on the DC side of the PS.

The sound is OK through line out connections. I was thinking that power supply is good.
Do you think that that cap is responsible for this malfunctions?
I'll check that.

 

[devol-toni]

Check your personal email, schematic sent to the address you supplied me

Received
Thanks bro