Yamaha CX 1000 preamp problems

[larbor]

I have a CX 1000 and I’m having a problem with the MC phono stage. I just started using the stage again for my Denon DL-103 cartridge and I’m getting a strange sound when I switch over to phono. It sounds like feedback, but sometimes it’s a whining noise. If I switch the ohms settings back and forth it goes away (I just turn the selector back and forth). It doesn’t matter if the turntable is plugged in or not, and it only happens on the MC setting. It might be effecting the sound also (not sure). All the other analog settings work great.

Just wanted to know if anybody is having (or had) the same problem? Maybe the phono stage needs a recap?

Thanks

 

[avionic]

I have a CX 1000 and I’m having a problem with the MC phono stage. I just started using the stage again for my Denon DL-103 cartridge and I’m getting a strange sound when I switch over to phono. It sounds like feedback, but sometimes it’s a whining noise. If I switch the ohms settings back and forth it goes away (I just turn the selector back and forth). It doesn’t matter if the turntable is plugged in or not, and it only happens on the MC setting. It might be effecting the sound also (not sure). All the other analog settings work great.

Just wanted to know if anybody is having (or had) the same problem? Maybe the phono stage needs a recap?

Thanks

Sounds like a dirty switch...

 

[for_p1]

I have a CX 1000 and I’m having a problem with the MC phono stage. I just started using the stage again for my Denon DL-103 cartridge and I’m getting a strange sound when I switch over to phono. It sounds like feedback, but sometimes it’s a whining noise. If I switch the ohms settings back and forth it goes away (I just turn the selector back and forth). It doesn’t matter if the turntable is plugged in or not, and it only happens on the MC setting. It might be effecting the sound also (not sure). All the other analog settings work great.

Just wanted to know if anybody is having (or had) the same problem? Maybe the phono stage needs a recap?

Thanks

Is it in one or both channels? This preamp has separate MC buster amplifier. Considering what you described, I would bet more on input transistors failing.

 

[avionic]

Could be..I'd try the switch first and inspect solder connections in the MC pre section.

 

[larbor]

It's in both channels. I did try to deOxit the switch but it was difficult to get to. Ended up just spraying in the area of the switch. Looks like I need to start unscrewing things to get in there. Do you know the location of the phono board (pictures would be great). Going to locate a service manual also.

Big thanks on the fast reply... hopefully I can figure it out.

 

[avionic]

The service manual is loaded into the AK manual database.


http://akdatabase.com/AKview/albums/userpics/10004/Yamaha CX-1000_CX-1000U_CX-2000 Service.pdf

 

[avionic]

Looks extensively "busy" inside that preamp..

 

[for_p1]

It's in both channels. I did try to deOxit the switch but it was difficult to get to. Ended up just spraying in the area of the switch. Looks like I need to start unscrewing things to get in there. Do you know the location of the phono board (pictures would be great). Going to locate a service manual also.

Big thanks on the fast reply... hopefully I can figure it out.

If both channels, I would check power rails first. Could be something wrong with power regulator. Yamaha's circuits tend to oscillate when power drops below certain level.