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Author Topic: 10K Audio pot with 120V switch  (Read 4360 times)
KE4JOY
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« on: June 17, 2013, 01:19:05 PM »

Trying to find a replacement AF gain pot 10K ohms but has a 120V AC switch built into it.

Tried lookin through mouser but couldn't find anything with a 120V rated switch in it. I need to replace the existing one as it has gotten pretty noisy and intermittent.
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KE3WD
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« Reply #1 on: June 17, 2013, 01:31:41 PM »

These guys specialize in restoration parts for the boat anchors: 

http://www.tubesandmore.com/search/node/potentiometer%2B10K

You should also find out the taper.  Log taper for most volume control stuff, linear taper may be found if the pot is controlling something besides volume. 

Part number stamped on old pots may be a clue as to taper, A suffix indicating the logarithmic audio taper, B indicating linear taper. 

But it is easy enough to find out using your ohmmeter as well.  Connect to one end of pot and wiper.  Turn pot such that you are measuring the entire resistance.  Then turn shaft to exactly the halfway point and if it reads half of the total, it is a Linear Taper pot. 


73
« Last Edit: June 17, 2013, 01:40:37 PM by KE3WD » Logged
KE4JOY
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« Reply #2 on: June 17, 2013, 01:52:54 PM »

Very nice source, many thanks.

This looks like a pretty good match although its a push/pull on off, no biggy but I cant find what the switch rating is for?
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KD0REQ
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« Reply #3 on: June 18, 2013, 10:11:19 AM »

Mouser has lots of Alpha pots with 120/240 volt turn switches.  the shaft is metric, not inch, so your knobs will have a very slight off-center wobble as you turn them.  but it will be new, and it will work.
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KE4JOY
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« Reply #4 on: June 18, 2013, 12:56:29 PM »

Mouser has lots of Alpha pots with 120/240 volt turn switches.  the shaft is metric, not inch, so your knobs will have a very slight off-center wobble as you turn them.  but it will be new, and it will work.

Huh I couldnet find them, I guess my search skills are lacking. I will try again.
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KE4JOY
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« Reply #5 on: July 05, 2013, 09:23:47 AM »

I found this

http://www.mouser.com/Search/ProductDetail.aspx?R=RV170SF-10-15R1-A10Kvirtualkey14860000virtualkey31CC401-F

But note the switch is rated 1 amp at 12 volt. I dont know if this will be suitable for switching 120V at a few ma.

Im still looking for one with a 120V rated switch.
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KE3WD
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« Reply #6 on: July 05, 2013, 09:52:09 AM »

That switch should not be used to switch 120VAC. 

You can't find one at Antique Electronic Supply?  They specialize in components needed to restore vintage radio sets. 


73
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KE4JOY
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« Reply #7 on: July 05, 2013, 01:55:15 PM »

That switch should not be used to switch 120VAC. 

You can't find one at Antique Electronic Supply?  They specialize in components needed to restore vintage radio sets. 


73

They had this  http://www.tubesandmore.com/products/R-VC10KA-PP

But nowhere does it say the switch rating. All the 10K pots at mouser that have 120v rated switches are not stocked.
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KE3WD
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« Reply #8 on: July 05, 2013, 03:35:33 PM »

That pushpull from Antique Electronics is very likely to be raed for 120VAC, consider that their specialty is radios and amplifiers from the boat anchor era when switches were switches, men were men and the women were glad of it.  

That, and it is highly unlikely that those folks would even conceive a need for a low voltage switch on a pot...

Seriously, I can tell from the construction seen in their pic that the switch inside that black composition is an AC rated switch.  

Eight Dollars is a lotta dough, though, this old man remembers when such was less than a buck and available everywhere. 

TIP  -- most of the older pots with switches at back were meant to be rebuilt,  tabs generally held the switch mechanism to the pot and outfits used to sell replacement switches only.  Might be possible to remove a good working switch assembly from another pot that isn't the right value and transplant it to yours.  Also might be possible to do a bit of careful investigative surgery on your broken switch mech and put it to rights and not have to buy a new one. 

73
« Last Edit: July 05, 2013, 03:39:19 PM by KE3WD » Logged
KE4JOY
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« Reply #9 on: July 05, 2013, 04:12:33 PM »

The switch is fine its the pot that is noisy/intermittent.

I thought about tearing it down for a 'rebuild' but it is sort of working at the moment just requires the occasional jiggle.

I am considering making a kludge with a 120v rated relay with the lv switch pot the current is minimal. I have LV source avail in the rig so it would not be all that hard. I am really trying to avoid adding a seperate on off switch but that may be a consideration.
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K2OWK
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« Reply #10 on: July 05, 2013, 10:20:21 PM »

Try Deoxit on the pot. I have restored many boat anchor radios and this chemical does wonders on noisy pots and switches.

73s

K2OWK
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G3RZP
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« Reply #11 on: July 06, 2013, 06:12:10 AM »

I've certainly had a lot of success with switch cleaner on noisy pots, so it would be worth trying K2OWK's suggestion.
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KE3WD
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« Reply #12 on: July 06, 2013, 07:56:27 AM »

Oh my. 

By all means try a squirt of Deoxit on the pot, through the little slot next to the lugs.  Rotate the pot immediately ten to twenty times while the cleaner portion is still wetting the internal contacts of the pot to get that mechanical wiping action to work for you.  After the cleaner solvent evaporates, Deoxit leaves behind some lubrication designed for the purpose.


I keep also one of the tiny bottles of DEOXIT 100 on my bench, if the standard spray doesn't do the job, a wee drop of the 100% Deoxit often does. 

And if the above were to fail, I would not hesitate to disassemble the old fashioned pot with switch in an effort to find out why.  Examination of the center wiper often reveals that it is just caked up with goo or corroded, a light swipe with a piece of fine grade Scotchbrite or equivalent, reassemble and then apply Deoxit spray to lube things before turning the pot. 

Also examine the carbon trace for cracks.  Cracked trace is time to get another pot.

And -- since you have an operating switch, you could move tha switch to *another* pot of the same type and manufacturer rather easily.  Have done that plenty of times. 

73
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KE4JOY
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« Reply #13 on: July 06, 2013, 10:12:10 AM »

Thanks for the advice all, now that I finished the 'sweep' for 13 colonies I will try some of your suggestions.

Many thanks.
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KE4JOY
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« Reply #14 on: July 06, 2013, 11:32:25 AM »

Couldent modify the previous post but it is fixed. Thaks for the advice. Took it apart, cleaned it, applied some no ox, spread the fingers a tad and put it back together. Now its smooth as butter. Many thanks.
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