How to clean switch on Vintage 70's Board

[telehumbucker]

Problem channel on Vintage 70's Midas board has a switch that has problems. I posted a picture of the switch below - a side view and top view. What is the recommended method for cleaning this type of switch? When I switch through the Khz options on the switch and rotate the treble knob, the channel lights up........it's the same channel I posted about where there is no signal from the line or mike inputs.....so may be related to that.....

 

[Ike Zimbel]

Best to just replace it. It looks like the bottom terminal may be cracked anyway. Just to make life even more interesting...be aware that the blue Hellerman sleeves (the rubber sleeves) can become conductive with age. Easy to test, just touch the leads of your DMM to them...they should read open circuit. If you read any kind of resistance, cut them off with a blade.

 

[telehumbucker]

Best to just replace it. It looks like the bottom terminal may be cracked anyway. Just to make life even more interesting...be aware that the blue Hellerman sleeves (the rubber sleeves) can become conductive with age. Easy to test, just touch the leads of your DMM to them...they should read open circuit. If you read any kind of resistance, cut them off with a blade.

The mic line switch, I was told in the other thread may be bad...it's the same type of switch....where do I find replacement switches? Any recommendations on suppliers?

Thanks

 

[Ike Zimbel]

Those are C & K 7000 series. A quick search turned up 7201SYZQE as the probable part number, but you'll want to double check the features. Digi-Key is my go to, but Mouser and Newark should have them as well.

 

[telehumbucker]

Thank you so much for that; truly appreciated.

 

[Ike Zimbel]

Is it the three position Frequency select switch? If so, I definitely gave you the wrong p/n as that's for a 2-position switch. You will still be looking for a 7000 series switch though.

 

[telehumbucker]

Is it the three position Frequency select switch? If so, I definitely gave you the wrong p/n as that's for a 2-position switch. You will still be looking for a 7000 series switch though.

Yes, it's a three position switch.....The mic/line switch is a two position switch, so that should be the right switch for that....

 

[telehumbucker]

Is it the three position Frequency select switch? If so, I definitely gave you the wrong p/n as that's for a 2-position switch. You will still be looking for a 7000 series switch though.

I'm trying to figure out how to remove the switch. In the picture you can see that there is a round smooth metal covering that meets the board's surface and covers the bottom portion of the switch.....how does one get that off? I'm assuming there is a way to twist it off, but there is no way to grip it, as it's tapered and smooth......Some of the other switches on the board have washers that are on a threaded stem and it's obvious how to remove them...but these one's are a mystery.

 

[Ike Zimbel]

Just turn the switch, after you take the leads off (and carefully document where they go!!!! Take Pics!).

 

[telehumbucker]

Just turn the switch, after you take the leads off (and carefully document where they go!!!! Take Pics!).

So I don't have to take the smooth dressing nut off? Does the dressing nut twist off by turning the switch from below? The dressing nut on top of the board covering the switch is too smooth to get a grip.....I asked a tech guy at digikey how to get the dressing nut off and he didn't know. Some of the C&K dressing nut models have a flat area that you can grip but the ones on the board don't. Tried calling C&K and couldn't get anyone on the phone.

 

[zamproject]

Some of the C&K dressing nut models have a flat area that you can grip but the ones on the board don't

IIRC had the same issue on 089 fader start switches...
Used the most convenient pliers available around with rag to not mark the nut
Removing the pot knobs may help for better access/grip.

Good luck
Zam

 

[Ike Zimbel]

So I don't have to take the smooth dressing nut off? Does the dressing nut twist off by turning the switch from below? The dressing nut on top of the board covering the switch is too smooth to get a grip.....I asked a tech guy at digikey how to get the dressing nut off and he didn't know. Some of the C&K dressing nut models have a flat area that you can grip but the ones on the board don't. Tried calling C&K and couldn't get anyone on the phone.

The nut will come off as you turn the switch. The new ones have flats to get a wrench on. The old ones used to rely on a backing nut on the other side of the panel...so, you would thread the dress nut on all the way by hand, and then tighten the backing nut against the panel from behind to make it tight. We had more time on our hands back then...

 

[zamproject]

The nut will come off as you turn the switch.

From the picture the switch look very close to the bended side of the front panel, not sure you get that room to tun it...

 

[Brian Roth]

From the picture the switch look very close to the bended side of the front panel, not sure you get that room to tun it...

Indeed!!!!!!

Bri


Old joke "No user serviceable parts inside"

 

[zamproject]

Another possible try is some time in the freezer to retract all parts...

Old joke "No user serviceable parts inside"

The bad joke being if those switches were just mounted by hand with soft torque but with thread lock...

 

[transient]

You could try flowing some contact cleaner (DeoxIT, etc.) through the top, down the sides of the lever. The lever will press down slightly, with light finger pressure, to facilitate this. Then exercise a few times - and exercise the switch too.

 

[Ike Zimbel]

You could try flowing some contact cleaner (DeoxIT, etc.) through the top, down the sides of the lever. The lever will press down slightly, with light finger pressure, to facilitate this. Then exercise a few times - and exercise the switch too.

To the OP, the above is a suggestion for cleaning the switch, not removing it.

 

[Dreams]

Most of the front panel controls on these are a bit of a pain to cleanly take out or put in. When i work on these i desolder the wires and connect them to a known-good pot/switch to test first. With this method, most commonly the problem ends up being something else, second most common is that i find a broken wire

 

[transient]

To the OP, the above is a suggestion for cleaning the switch, not removing it.

True. I could have been more explicit but the original query was about cleaning. I have found that most switches of this type can be restored using the method described with no need for dismantling.

 

[nsalis]

Which Midas model is it? This would help to find the order number for the 3-position switch.