Yamaha C-6 Humm in both channels HELP!

D

derhussl

New Member
Hey guys,

I am hoping someone can help me I just got this c-6 hooked it up today and I have humm in the line both channels a little more in the right then the left but pretty consistent.

I did some basics like disconnect everything except for the amp and the preamp and it still humms the same.

Any idea what this could be.

I am using a knewood KM-207 amp and this preamp. It initially sounded ok but I turned it off and on once and fiddles with the record pot and now I have this going on.

Any help would be appreciated!
 
I don't know anything about the C-6 specifically, but if Yamaha used their metal topside buss bars to connect power and ground, sometimes the solder joints aren't up to snuff where they connect to the larger traces and grounds. Might not be it at all, but something to look at. Easy to touch up with a hot iron and decent rosin flux.
 
YAMAHA C6 Humm in both channels HELP !

Hello !

is this noise changing with volume control ? :scratch2:
 
Did you try replacing the cables between the preamp and amp? Maybe it isn't the preamp at all.
If the cables are ok, you probably did something when you messed with the record pot. Try turning that back and forth a bunch of times, maybe it's dirty.
Maybe it has nothing to do with the pot, maybe it's a problem in the power supply or a loose screw that provides the ground for one of the circuit boards.
 
I tried replacing the cables with different ones and its still the same. I basically did all the simple stuff. Replaced the cables put in a different amp entirely disconnected all the inputs and just had the amp and the preamp on and it still humms even with out anything else being connected.

I also went and put deoxit on the record pot and fiddled with it and its still the same. The volume has not effect on it either way. I can turn the knob all the way down and still the humm I can crank it to max and still the same humm.

Sorry I should have geve you guys all of those specifics before posting.

Conrad what do the topside buss bars look like?
 
Last edited:
Check for cracked solder connections on the RCA jacks. Like Vint said, it may have a bad cap or two in the power supply. Or even cracked solder connections in the power supply circuit.
 
thanks guys I am going to check the power supply board and see if I can see anything that seems out of place or loose or something.

Thanks for the help!
 
You may not be able to see the bad joints unless you have lot of experience looking at this stuff. Look for joints where the solder looks like a ball on the heavier traces. It should flow and have a small fillet. Ultimate you may just have to touch some up to be sure.
 
Thanks Conrad

I found something loose could this be the problem? I circled it in red. When I was looking I noticed its extremely loose.

loosepiece.JPG
 
Also does anyone know what portion of the board is for the power supply? I am guessing its where the loose piece is?
 
The voltage regulator's legs are loose. Check their solder connections (the two transistors mounted to the black heatsinks you have encircled). I would also replace the two big PS caps in the rear.
 
thanks I alread ywent and got the replacement caps and I am going to pull that regulator and resoder it and see how that goes.

Will let you guys know how that turns out :)

thanks for all the help
 
Well s somehow I made things worse :(

I replaced the Big PS caps and resodered the voltage regulator.

Fired her up and now I am getting humm but where before it was not tied to the volume now it gets louder by turning the volume up. Also the right channel is dead unless I go in to mono or if I turn the defeat on it works so not sure where to go from here or what I touched that did that. Any of you Yamaha gurus have any ideas.
Seems I blew it up worse.
 
derhussl said:
Well s somehow I made things worse :(

I replaced the Big PS caps and resodered the voltage regulator.

Fired her up and now I am getting humm but where before it was not tied to the volume now it gets louder by turning the volume up. Also the right channel is dead unless I go in to mono or if I turn the defeat on it works so not sure where to go from here or what I touched that did that. Any of you Yamaha gurus have any ideas.
Seems I blew it up worse.
Click to expand...

Do not power it up again. Inspect the caps you replaced and make sure you installed them in the correct polarity. There should be markings on the board. If the caps cover the markings you'll have to remove them and check. Use de-soldering braid to remove them.
 
Yeah I did that I installed them with the white stripe pointing in the same direction as the old ones. I may just desoder these anyways and put the old ones back in and see what happens.

Is that a thought?
 
derhussl said:
Yeah I did that I installed them with the white stripe pointing in the same direction as the old ones. I may just desoder these anyways and put the old ones back in and see what happens.

Is that a thought?
Click to expand...

First tell me the name of the manufacturer of the new caps and I'll tell you if there is any reason to think they are defective.
 
Says Jackcon

I flipped the old ones back in and its the same so I would say that wasnt the issue anything else I can try?
 
derhussl said:
Hey guys,

I am hoping someone can help me I just got this c-6 hooked it up today and I have humm in the line both channels a little more in the right then the left but pretty consistent.

I did some basics like disconnect everything except for the amp and the preamp and it still humms the same.

Any idea what this could be.

I am using a knewood KM-207 amp and this preamp. It initially sounded ok but I turned it off and on once and fiddles with the record pot and now I have this going on.

Any help would be appreciated!
Click to expand...

What does the amp (Kenwood)sound like when the control amp(C-6) is disconnected ?
 
derhussl said:
Says Jackcon

I flipped the old ones back in and its the same so I would say that wasnt the issue anything else I can try?
Click to expand...

I wouldn't use those. Panasonic, Nichicon, Elna are what you want to use. I think you bought some Chinese caps. Probably not the problem but I wouldn't put them in anything I worked on.
 
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