Mcintosh MX-110Z Loose Power Knob?

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Hello AK'ers,

Just a quick question about my MX-110Z. There's a bit of play/wiggle-room in the power knob, is this normal? If not, how do I go about fixing this?

Thanks!
 
The power switch is mounted to the back of the Balance pot. If there is play in the shaft, this would indicate a problem with the assembly as a whole.

Can the power knob be easily pulled off? If so, you may have play in the friction-fit of the shaft to the knob. This is far easier to rectify. Pull the knob and see what is happening with the shaft's play.

Generally, I have been recommending that the power switches not be used at all. The best arrangement is to solder a jumper across the power switch leads and leave it in the off position. This keeps any current from flowing across the switch's contacts. If the power switch fails by contact arcing, the entire Balance control could be damaged. You protect the MX-110 by not relying on the power switch with the jumper.

This means, you'll then use an external power switch such as that found on outlet strips to control power to the unit.

Cheers,

David
 
The power switch is mounted to the back of the Balance pot. If there is play in the shaft, this would indicate a problem with the assembly as a whole.

Can the power knob be easily pulled off? If so, you may have play in the friction-fit of the shaft to the knob. This is far easier to rectify. Pull the knob and see what is happening with the shaft's play.

Generally, I have been recommending that the power switches not be used at all. The best arrangement is to solder a jumper across the power switch leads and leave it in the off position. This keeps any current from flowing across the switch's contacts. If the power switch fails by contact arcing, the entire Balance control could be damaged. You protect the MX-110 by not relying on the power switch with the jumper.

This means, you'll then use an external power switch such as that found on outlet strips to control power to the unit.

Cheers,

David

It's definitely not the knob, the shaft has some play to it even if the knob is off. I'm using a power conditioner/voltage regulator right now that doesn't have an on/off switch, so I'm thinking of potential solutions :(
 
Hello David, could you elaborate a little about exactly where the jumper might be placed?

Thanks.

Sure. There are 2 connections on the back of the Balance control. These will have 2 wires fed to them from the back of the chassis. Trace those wires back and you'll see they are part of the AC input wires from the AC cord. Some of those wires will also go to the outlets on the rear panel originally intended to handle other amps and gear.

Solder a wire between the 2 connections on the back of the Balance control. In other words, short them out. What this does is to render the ON/OFF knob useless since the unit will not come on as soon as you apply AC power to the AC cord itself.

What you are also doing is to provide a low resistance path for AC power without the current running through the switch on the Balance control. You want to leave the ON/OFF switch itself in the OFF position to keep the switch contacts open so there is absolutely no current being run through the contacts. This forces all AC current to go through the short you just installed.

To power the MX-110, then, just use an external power strip with its own switch on it. This is what I do. Works great and the ON/OFF-Balance control does not run the risk of arcing contacts which, when hot enough, can burn up the Balance pot.

Hope that helps.

Cheers,

David
 
Sure. There are 2 connections on the back of the Balance control. These will have 2 wires fed to them from the back of the chassis. Trace those wires back and you'll see they are part of the AC input wires from the AC cord. Some of those wires will also go to the outlets on the rear panel originally intended to handle other amps and gear.

Solder a wire between the 2 connections on the back of the Balance control. In other words, short them out. What this does is to render the ON/OFF knob useless since the unit will not come on as soon as you apply AC power to the AC cord itself.

What you are also doing is to provide a low resistance path for AC power without the current running through the switch on the Balance control. You want to leave the ON/OFF switch itself in the OFF position to keep the switch contacts open so there is absolutely no current being run through the contacts. This forces all AC current to go through the short you just installed.

To power the MX-110, then, just use an external power strip with its own switch on it. This is what I do. Works great and the ON/OFF-Balance control does not run the risk of arcing contacts which, when hot enough, can burn up the Balance pot.

Hope that helps.

Cheers,

David

Hello David, thanks for the info. Getting to the back of the switch looks like it would require removal of that switch, don't really want to do that.

Wouldn't it be the same result if I solder a wire between where those 2 brown wires terminate at the aux power plugs? (i.e., from the red plug to the black plug next to it). Actually, it would make sense to just disconnect the brown wires from those plugs and solder a wire across? (also notice the CL-90)

Thannks for the help!
 

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That can also work at that point, too. As long as there is no current flowing through the switch on the back of the Balance control, you're achieving the objective.

The CL90 was not stock and was added by someone who has likely read the discussions here at AK about its value.

Cheers,

David
 
That can also work at that point, too. As long as there is no current flowing through the switch on the back of the Balance control, you're achieving the objective.

The CL90 was not stock and has been added by someone who has likely read the discussions on it here at AK.

Cheers,

David
 
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