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OT Volume control cleaner

Joined
Nov 19, 2007
Location
marysville ohio
My ancient Harmon Kardon crackles and pops something fierce when you change the volume or balance. You used to be able to buy cleaner / lubricant for these old style volume controls at Radio Shack. They are gone now and it seems the cleaner is as well. Is it still available somewhere?
 
Deoxit D5 from amazon or similar, worth every penny. Some follow up with the Deoxit G5 which has some persistent lubrication properties, but the D5 stuff is the bees knees for potentiometer noise.

The usual procedure is to spray into the pot body, work the knob back and forth a few times, repeat until the noise goes away. Orient the unit so the drips coming out fall away and don't get all over the circuit boards etc.

While I'm in an old stereo, if its dirty I often give it a bath of hot water and scrub it with a paint brush and dish detergent, rinse with hot water, then a couple rinses with 90% isopropyl alcohol to wash out the water, followed by a few days of air drying with a fan.
 
There are many types of contact cleaner available on Ebay. DeoxIT is one of them, with both a cleaner and a lubricant available.
 
spray electrical contact cleaner is common from other places. its basically a no residue solvent that evaporates leaving nothing behind. i use every day in a machine shop. many chucks and indicating tools get sticking when oil or anything in them. usually spray til dripping working it back and forth to get the stuff out and it will move freely.
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most industrial supply places sell it often called no residue electrical contact cleaner
 
I have a can made by CRC.
Stuff worked okay but errant fluid melted some of the black plastic surround on the old Panasonic tuner.
 
I tried to post inks to these dealers but it must have overloaded PM's brain because it kept rejecting the post. Anyway, try these-

Digikey

Allied Electronics

Newark Electronics

Mouser electronics

The product used to be called "Quietrol" but it doesn't seem to be available now. I'm sure there is something else replacing it. You want one that will leave a lubricant. I use Deoxid all the time. It is mainly for contacts. Sometimes just wiggling the control back and forth will rub the dirt off.

Bill
 
obviously read the can label electrical contact cleaner doesnt normally effect plastics.
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some spray cleaners like carburetor cleaner might be very powerful and damage plastic and rubber
 
Cleaner lube for variable potentiometers is a fast fix solution. If it works great. But if the problem returns quickly or becomes worse, you need to replace the control. The resistive compound is worn by the wiper contact and when it gets to thin it's over.

If you plan to keep the system, start looking for a replacement control.
 
I have had very good success over the years by using wd-40 to clean volume controls and switches. In my opinion it is one of the few things that wd-40 is good for. It's a lousy lubricant (long term) a pretty good cutting fluid for AL, works good to remove sticky label residue, a fair penetrating fluid etc. Works great on volume pots though.
 
DeOxit is awesome. Get some, you won't regret it. I bought a fingernail polish sized bottle with a built in brush years ago and use it all the time - might have used 1/8 bottle by now. There are a few varieties. Red has cleaner built in along with lubricant. There is a variety made JUST for pots also.
 
Cleaner lube for variable potentiometers is a fast fix solution. If it works great. But if the problem returns quickly or becomes worse, you need to replace the control. The resistive compound is worn by the wiper contact and when it gets to thin it's over.

If you plan to keep the system, start looking for a replacement control.

+1 My 1970's Marantz has soft detents on it's big rotary, I didn't expect to be able to find a modern-times replacement even with a Court Ordered search warrant.

Got a surprise once indoors. The big knob rolls a spring steel "tape" back and forth through a slipper guide. Down at the end of it, smack-dab in the no wire-leads low-noise center of the PCB sat common (Alps, Bournes) recording studio audio control board SLIDE potentiometers.

Easy replacement after all, even cheap.
 
My mind boggles that those steel tape rotary switches/slide systems work as well as they do. Have yet to see one fail despite age and knuckle-dragger tech repairs though they do get sticky etc.
 
My mind boggles that those steel tape rotary switches/slide systems work as well as they do. Have yet to see one fail despite age and knuckle-dragger tech repairs though they do get sticky etc.

The key to it, one supposes, is that they are mechanically stressed to perhaps less than twenty-percent of the strength of the goods.

If "right size" Engineered down to the far more slender riband yet that is all it really takes to move the silly slider, they'd be too costly in overly touchy labour to install, so oversized they went!

FWIW-nothing-really I've been playing with Kevlar & cousins pirated from spools of string-trimmer weed-whacker cord (doesn't razor-blade the fingers, y'see..) to adapt a largish assortment of different travel lengths of slider potentiometers to 10EE on-apron Armature+Field RPM control, base & below range up into the balancing act of "Field Weakened" range.

The payout/retract "drum", y'see can have a cam profile, even conical "windlass worm" such that degrees of rotation and movement of slider are dynamically selectable, and divorced, one from the other, rather than be commoned-up to a single right circular cylinder.

A de facto "mechanical" taper is produced. Two, actually. Both more easily altered than complementary resistive element tapers as want far more labour to alter the skew of.

Games. The more interesting ones are usually those a person invents for their own amusement rather than buy "LCD focused [1]" as well as a different "LCD" equipped[2] air-head toys at the local El Cheapo store.

:)

[1] Least Cornfused Discombobulated - a population metric, apparent intelligence, or lack-thereof, relevant and generally a more outrageous lie than the averages for lies as well as the averages for its allegedly dumb-ass subjects.

You know who those idiots are. The ones with nicer homes, faster motorsickles, newer and bigger pick-up trucks, more money in the bank, and hotter bed-partners. Too pig-dumb to score high on IQ tests, the crafty bastards went off, found a job they could actually HANDLE, and simply WORKED harder than the ivory-tower pointy-haired entitlement-riders who presume to predict their behaviour as if they were hydraulic fluid, rather than somewhat more anarchistic than feral cats.

Hence the figures lie over whom it be that is actually the "dumb ass" and why Presidential elections can surprise.

[2] Liquid Crystal Display - just what it says it is, though Crystals Suspended in Liquid, "CSL" or "LSC" for Liquid Suspension of Crystals might have been functionally the clearer description.
 
CRC electronics cleaner is available in the automotive section of Walmart for about $4. Works great and I have had no issues with it eating plastics.
 
I've got an 1976 era Panasonic am/fm/8track stereo (can record 8 tracks, even!!!!) that the volume control is horrible on.
I guess Panasonic was the cheap version of Pioneer back then. Anyhow, it's a good unit for playing music in the shop.

I did some asking about it once and I was told that the control is not a wire wound pot, but some sort of fiber disc with a carbon surface that a "feeler" rubs on as you turn the knob. .and that as it ages the carbon contact surface is crumbling and not making complete contact... and that is what the problem is. No cleaner was going to do that any good is what I was told...

If you find a good place on it while turning it, it's best to just leave it at that volume and not mess with it ;)
 
If the problem persists after cleaning, it's time to look at whether there is a DC offset present on the audio signal going thru the pot. This is usually tamed by capacitors, but they are commonly bad on older gear. Cap fails, DC encroaches on signal, and running DC thru audio pots is a guaranteed noisemaker. A scope can find this, or even a voltmeter.

Though I don't have a schematic for that, it's highly unlikely that the designers allow DC thru the pots.

It's not hard to replace caps. The difficulty is in disassembly/reassembly without bustin' stuff.
 
If the problem persists after cleaning, it's time to look at whether there is a DC offset present on the audio signal going thru the pot. This is usually tamed by capacitors, but they are commonly bad on older gear. Cap fails, DC encroaches on signal, and running DC thru audio pots is a guaranteed noisemaker. A scope can find this, or even a voltmeter.

Though I don't have a schematic for that, it's highly unlikely that the designers allow DC thru the pots.

It's not hard to replace caps. The difficulty is in disassembly/reassembly without bustin' stuff.

I'v had this receiver since 1972, It may be time to move on but it sounds great as long as you don't touch the volume, balance, bass or treble. It could take 5 minutes of messing around to make it happy again.
 
On this vintage unit the volume and tone controls are usually capacitor coupled with interstage buffering transistors. More evolved designs up the tone controls in the feedback loop, later on using op-amps for better buffering thru the pre-amp sections- but pretty much always cap coupled- so no DC or at least only miniscule leakage.

An unserviced unit this old generally benefits from a look in to check the idle current/DC offset. Sometimes all caps are fine other times a thorough recap is needed.
 








 
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