Yamaha C-80 lost sound switching inputs

[Soundscape]

In my hobbyist experience:
Scratchy sounding controls are just dirty controls.
Pops have proven to be cracked carbon tracks and a PITA

We all need to bug Alps/Alpine to build us some new ones. Let's mass blast them some emails!
EDIT: In fact, If someone would be kind enough to post the part number I'll be the first to write them.

 

[ghankstef]

It sounds to me like there's a cracked carbon wafer board in the loudness gang pot. Cleaning won't fix that so I hope I'm wrong. Has this volume control taken a wack? These get damaged alot.

Can ya please post a photo of the top of the pot case to stir my memory? I do remember they're sealed and sealed for a reason. IIRC, mine had a couple holes on top to shoot in some de-ox via syringe.

Here it is. I did inject contact cleaner in there multiple times and really work the volume and loudness knobs back and forth a lot. They are smooth now. No signs it didn't take a wack. Was shipped to me nicely in styrofoam and all. Doesn't mean it didn't take a wack at some point. Looks like I need to get that opened up and inspect the wafer board. Wondering if it is damaged if worse case I can bypass the loudness. Would be a shame but better than not working at all.

 

[Soundscape]

Here it is. I did inject contact cleaner in there multiple times and really work the volume and loudness knobs back and forth a lot. They are smooth now. No signs it didn't take a wack. Was shipped to me nicely in styrofoam and all. Doesn't mean it didn't take a wack at some point. Looks like I need to get that opened up and inspect the wafer board. Wondering if it is damaged if worse case I can bypass the loudness. Would be a shame but better than not working at all.

Thanks for the photo sir.

I did inject contact cleaner in there multiple times

I did a similar thing. I also let the piece sit on the bench for a couple days upside down to drain the sauce out. Slightly propping one side for awhile, then the other. Working the turns inbetween steps. I'm really hoping that pop is just from excessive cleaner/sauce.

 

[Soundscape]

I thought my C-80 and C-65 had more gangs than that. Mine looked like a smurf condominium and longer. Doesn't matter. If everyone shows their part numbers on what they have...C-85/80/65/60, I will bug the F out of Alps/Alpine for these.

 

[ghankstef]

Thanks for the photo sir.



I did a similar thing. I also let the piece sit on the bench for a couple days upside down to drain the sauce out. Slightly propping one side for awhile, then the other. Working the turns inbetween steps. I'm really hoping that pop is just from excessive cleaner/sauce.

I let it drain overnight up side down

 

[Soundscape]

Is your shaft bent? Some C-80 guys suffer from that. Knob will wobble during turns if it's bent.

EDIT: Esoteric shaftisms

 

[ghankstef]

Is your shaft bent? Some C-80 guys suffer from that. Knob will wobble during turns if it's bent.

EDIT: Esoteric shaftisms

What a question. Looks ok

 

[Soundscape]

What a question. Looks ok

I don't say that to all the guys...

 

[ghankstef]

Ok kind of a lot of work just to get this bad boy free. I can see there are really 6 pots here. I could only access 4 without getting it free. I have flushed it with contact cleaner - the fast drying plastic safe kind and then a shot of fader lube. Then I worked the pots back and forth for a long time - like an hour while watching some vids.

I think I will solder it back up and test it tomorrow. If that isn't enough then we are looking at getting the whole thing apart and cleaning each carbon track individually and scoring the metal ring around it with a fiberglass pen. Apparently you need a special tool just to get it open.

These vids show how:

this one not in English and you can start a minute or so in.

This one is in English - not the same kind of pot but the actual method of cleaning the pot is the same as far as I can see:

Hoping I can skip this as it will be as much work as the rest of the project in and of itself, but if it needs to be done it needs to be done.

 

[Sparkplug]

Hoping I can skip this as it will be as much work as the rest of the project in and of itself …

If you’re certain this is the problem, then it’s worth the effort.

Working on my C-70, the volume turned out to have non-rotational free play in its shaft (slight wobble) that created noise, audio cuts, and irritating sound artifacts. I ended up opening it and eventually transferring (transplanting really) the wafers inside to another newer Alps volume with the same housing to solve the issue. In your case, however, these 2-in-1 housings are hard to come by new or at least I haven’t really looked for them. 2-gang Alps volumes are available from Mouser, identical housing.

Also remember, many of these Alps inside Yamaha equipment, have special tapers other than linear or logarithmic, many are special logarithmic and replacing them has huge effect on the volume and the output sound, in a bad way. I replaced my C-70 volume with a new A-curve Alps (identical housing) and the sound was miserable, hence the transplant of wafers.

 

[ghankstef]

If you’re certain this is the problem, then it’s worth the effort.

Working on my C-70, the volume turned out to have non-rotational free play in its shaft (slight wobble) that created noise, audio cuts, and irritating sound artifacts. I ended up opening it and eventually transferring (transplanting really) the wafers inside to another newer Alps volume with the same housing to solve the issue. In your case, however, these 2-in-1 housings are hard to come by new or at least I haven’t really looked for them. 2-gang Alps volumes are available from Mouser, identical housing.

Also remember, many of these Alps inside Yamaha equipment, have special tapers other than linear or logarithmic, many are special logarithmic and replacing them has huge effect on the volume and the output sound, in a bad way. I replaced my C-70 volume with a new A-curve Alps (identical housing) and the sound was miserable, hence the transplant of wafers.

Ok really good to know. Was wondering if I could do something like that worst case. Not 100% sure this is the problem but it looks that way.

I just measure the pots with a multimeter/ohm meter. I think the first 2 pots closest to the front are for loudness. When I move the loudness pot shaft to the right the resistance lowers. That seems like the expected result. The last 3 pots do the same for the volume knob. I haven't been able to read the schematic well enough to figure out what the actual values should be though.

pot	loudness all the way left	loudness all the way right
first pot closest to front	45.6 kohm	28ohm and dropping
second pot	45.4 kohm	38 ohm and dropping

Then the last 4 measure about 45 kohm with volume all the way to the left and under 1 ohm all the way to the right. Seems encouraging. That loudness to the right measurement doesn't stabilize though - wondering if that is a bad sign.

 

[Sparkplug]

According to the schematic, see below, the first pot is balance (orange highlight, 200K/MN curve), the second is volume (green highlight, 10K/special taper), and the last pot is Loudness (blue highlight, 50K/A-curve).

For balance, as the resistance increases in one channel, the other one decreases.

 

[ghankstef]

After attempting to clean the volum/loudness pot without taking it all apart I soldered it back in and tested it. I had sound and the loudness was working. The volume and loudness pots were noisy though.

Then I saw the subsonic filter was pressed in so I depressed it and pop at the speakers and no more sound. So I cleaned it with contact cleaner and this morning I had sound again. Now the loudness is back to cutting out if I rotate it about 20% counter clockwise.

So, I think I need to get this pot apart and clean it the hard way.

 

[Soundscape]

So, I think I need to get this pot apart and clean it the hard way.

Bummer. This may sound unrelated and probably is. Let's just call it a maintenance reminder while in there. Recommend cleaning the balance control pot. I imagine ya already did.

Sometimes ya get lucky. I bought one of these cheap over that balance pot being dirty and bent. Prior owners damage that pot alot. Good luck

 

[Soundscape]

To exhaust ancillary ideas. I'd clean the headphone jack. May sound as silly as post #74 but I like to weed out every external possibility before doing deep dives into anything. Shootin trbl from the outside in has served me well and hoping it's something simple sir.

Esoteric Redneckisms

 

[ghankstef]

Thanks! I did the balance pot a couple times but not the headphone jack . Will do

To exhaust ancillary ideas. I'd clean the headphone jack. May sound as silly as post #74 but I like to weed out every external possibility before doing deep dives into anything. Shootin trbl from the outside in has served me well and hoping it's something simple sir.

Esoteric Redneckisms

Already have it all apart at this point waiting for the deoxit, puller tool and fiberglass pen to show up.

 

[ghankstef]

To exhaust ancillary ideas. I'd clean the headphone jack. May sound as silly as post #74 but I like to weed out every external possibility before doing deep dives into anything. Shootin trbl from the outside in has served me well and hoping it's something simple sir.

Esoteric Redneckisms

You were asking for the part number think this is it or at least as close as I could find. Service manual says this:


part says something else (attached)

 

[Sparkplug]

What does it look like under that cover? What sort of lock washer did Alps use on this one? Can you post a photo? Thanks …

 

[ghankstef]

What does it look like under that cover? What sort of lock washer did Alps use on this one? Can you post a photo? Thanks …

Is this what you are looking for?
Post in thread 'Yamaha C-60 C-80 Volume Pot Cleaning' https://audiokarma.org/forums/index...c-80-volume-pot-cleaning.960917/post-14822015

 

[ghankstef]

So I tried something I put the volume and loudness pot in my ultrasonic cleaner with distilled water and isopropyl alcohol for 25 minutes. Took it out and let it dry about 6 hours. Pointed the hear gun at from a foot away for a minute or so.then added back a little fader lube. Did the same with the problematic subsonic switch. Soldered them back in.

Listening as I type sounds great but loudness pot is still noisy and still cuts out of I turn it down more than about a quarter of the way. Subsonic switch is still producing a pop but doesn't cut out sound anymore.

At this point I suspect the pots are damaged internally. 2 sets of 6. Wonder if I could find replacements just for the internal carbon track. My guess is it's not a matter of cleaning

Not sure if I want to open it up and go further or live with it. Sounds great on my test system at the moment. Fosi v3 amp and minimus 7 speakers.