fisher 400c volume issue

Discussion in 'Fisher' started by pioneergb, Jan 31, 2019.

  1. pioneergb

    pioneergb New Member

    Messages:
    7
    I have a 400c that was rebuilt about 3 years ago by Mikey Samra, it sounds great.

    Lately we are scratching our heads over a weird problem with the volume. When I turn on my system with the volume at it's lowest, the left channel is going to roughly 1/4 volume while the right stays normal quiet. If I move the volume control up the left channel catches up to the right at about 1/8 - 1/4 volume and then plays even. After awhile both channels start to play normal and I can turn the volume down with both channels working together.

    I do not use the volume control to shut the 400c on and off as I use a master control for phased start up and shut off. The upper adjustments to the volume (the little screws on top) are not in play as I am using aux 2 for my cd play and that does not have those adjustments in the circuit but I do have my phono plugged into Aux 1 using a phono pre and it has the same issue with volume.

    We are thinking the volume switch but hoping not...the volume control has been cleaned

    Any feedback would be appreciated
    Thanks
    Gary
     

     

    Please register to disable this ad.

  2. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

    Messages:
    9,900
    Location:
    Ball Ground, GA
    My own 400C developed a very similar problem a few years back, and unfortunately yeah, it was the volume control. One thing you can try which did help in my case for a while, is to carefully re-compress each of the volume control terminals, where they mount/wrap around a protrusion of the carbon track. That's how the terminals make connection to the track -- by way of having their mount tabs compressed together over where the track protrudes on the bakelite plate that both the track, and the terminal are attached to. Do all 10 terminals while you're at it.

    You can also try dabbing some full strength Deoxit on each of the compression connections to help ensure a good connection between the terminal and the track protrusion as well. But beyond these measures, there's not much else you can do but replace the control -- particularly if the problem is due to a hairline fracture in the carbon track.

    Good luck with it!

    Dave
     
  3. pioneergb

    pioneergb New Member

    Messages:
    7
    thanks Dave, I was hoping you would reply.

    Do you need to remove the control to do this?
     
  4. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

    Messages:
    9,900
    Location:
    Ball Ground, GA
    You might be able to get away with simply un-mounting the control, but leave the wiring (or most of it anyway) attached. When I did it, I used a good sized pair of needle nosed pliers to do the job. If you don't wish to remove any of the wiring, its not to terribly difficult to remove the entire front plate from the unit that the volume control mounts to, to help with access. The nuts and screws are all removed that mount the various controls, switches, and indicator lamps to the front plate, as well as the screws that mount the front plate to the side panels. It looks intimidating, but in reality is not that hard. Just take it slow and make notes of how everything was mounted.

    Dave
     
  5. pioneergb

    pioneergb New Member

    Messages:
    7
    400c volume control1a.jpg I was able to take it apart, you were correct not hard but you have to keep taking screws out until it releases, putting it back together should be interesting....my question is looking at these pictures what are the parts that need to be tightened? I did deoxit...am I better off just replacing the control, I am pretty sure Mikey has one to send me, but I can try what you are suggesting
    Gary 400c volume control2.jpg
     
  6. walyfd

    walyfd Well-Known Member

    Messages:
    734
    Location:
    Northeastern PA
    My 500b has been like this forever. Sound is always even at "OFF".
     

     

    Please register to disable this ad.

  7. dcgillespie

    dcgillespie Fisher SA-100 Clone Subscriber

    Messages:
    9,900
    Location:
    Ball Ground, GA
    You see how each terminal is attached to the bakelite disk with arms that come up through and around the outside edge, and are bent over towards each other to nearly meet in the middle? Use a pair of needle nose pliers to compress both the top and bottom sides of the terminal together, to help ensure a solid contact between the terminal, and the extension of the carbon arc it connects to other other side of the disk relative to your pic. I had previously said to do it to all 10 terminals -- there are in fact 10 terminals, but only 8 of them are mounted in this way. Disregard the middle terminal in each group of 3. Sorry for the confusion.

    It looks like somebody has been at that control before.

    Dave
     
  8. notdigital

    notdigital AK Subscriber Subscriber

    Messages:
    2,287
    Location:
    NYNY
    If what Dave has suggested doesn't solve the problem, and before you decide to toss the control, try tearing it down. There is sticky with very good pics on what you'd be up against if you're up to it.

    In my experience what has caused imbalances/noises/deadspots has been crap that has accumulated over decades of use and attempts to resolve issues with various cleaners. Another not so obvious cause is just plain wear on the carbon track. (See pic below of uneven wear on track.) If you go this route, clean everything (preferably with the correct stuff: Deoxit D5 for the metal, Faderlube for the carbon,) re-tension the contact tines, and reassemble. Before tossing the control on my 500c, I thoroughly cleaned it and voila, no more issues. It's a task not for the faint of heart so unless you enjoy doing that kind of work, do it as a last resort.

    DSCN2028.JPG
     
  9. pioneergb

    pioneergb New Member

    Messages:
    7
    Dave
    I figured that those were the tabs (for lack of a better word) you were talking about and I cleaned and tightened all of them except the middle two as you noted.
    I did have another issue a year ago with a wire that somehow got stripped and was grounding on the chassis, this was giving me full volume when turned on until I found that bare wire and I did clean up some solder issue and replaced a wire to the loudness control. It does also look like there were connections solders done to the top wires at some point, not sure if that was factory or not.

    The good news after putting it back together is the volume control is now working properly. I did a test last night, but more important as it seemed to be more of an issue was when it was cold in the morning. It past that test with flying colors, so far.
    I also noticed two other things that improved,
    1st it does not seem to have any volume when turned all the way down which it was doing before, not loud but you could hear it. This is good...
    2nd it seems to have cleared up most of the cross talk I was getting between aux 1 and aux 2 when one aux was being used and the other had nothing on.

    notdigital, I would try cleaning it if I have to dive in again, I was able to see what looks like the copper disk inside that your picture shows and was able to give it a good spray with the d5, once I had the switch somewhat exposed. I will say the thought of removing that switch does not excite me as those wires are all very tight and short, it will probably mean replacing some of those wires , which would probably make it somewhat easier to do.

    For others who may need to get to the switch it was not difficult but as Dave said earlier do it slowly and pay attention to what goes where. Also if you do need to remove the screws to the aux selector strip buttons be aware that there are round brass spacers that are behind those screws that will need to go back in upon assembly. Other that that remove screws until face plate comes loose with enough slack to move the volume pot..
     

Share This Page