Arggghhh! These pots are driving me mad!

[TimmyTonga]

I clean them and test them and the impedance runs smoothly from 0 -16 ohms as I turn. Then I put them in a cabinet and they are immediately intermittent. I mean immediately. Am I doing something stupid? Perhaps I need to bend the wiper more, because if I press gently on the black knob, contact is fine again.....

Any enlightenement out there?

Getting despondent and eyeing up L-pads.....

Tim

[owlsplace]

43 minutes ago, TimmyTonga said:

I clean them and test them and the impedance runs smoothly from 0 -16 ohms as I turn. Then I put them in a cabinet and they are immediately intermittent. I mean immediately. Am I doing something stupid? Perhaps I need to bend the wiper more, because if I press gently on the black knob, contact is fine again.....

Any enlightenement out there?

Getting despondent and eyeing up L-pads.....

Tim

RoyC would agree with you on the L-pads. Are you greasing the pots? I'm not fond of the idea mainly because I haven't found a suitable grease so I have just used de-oxit type of protective coating.

Roger

[TimmyTonga]

28 minutes ago, owlsplace said:

RoyC would agree with you on the L-pads. Are you greasing the pots? I'm not fond of the idea mainly because I haven't found a suitable grease so I have just used de-oxit type of protective coating.

Roger

I greased the pots on a set of 3as recently and the drop-outs happened, so this time I didn't - and they still happened!

Tim

[onplane]

I gave up on pots 8 years ago. I bypass the tweeter pot completely and use a padding resistor for the mid driver. This puts the mid pretty much in balance with the tweeter, but way behind the woofer.

I then bi-amp and apply more power to the mids/tweeter to bring them back in balance with the woofer.

Notice that I still have pots, but they are called volume controls and they don't corrode!

Regards,
Jerry

[genek]

I greased the pots in my 3a's with DeoxIT FaderGrease, which, IIRC from the MSDS is lithium with some "secret sauce" ingredients that Caig claims enhances conductivity. Haven't had any problems with them so far.

Bending the spring wipers might help with contact for a while, but the additional tension won't last unless you substantially deform the metal. 

[TimmyTonga]

During my time on the forum I have observed that Jerry never wastes an opportunity, and I respect that : )

Unfortunately my solutions are, in order;

• spray them with something

• substantially deform the metal

• replace them with something

• do something that someone has yet to suggest

• bi-amp

[owlsplace]

31 minutes ago, TimmyTonga said:

During my time on the forum I have observed that Jerry never wastes an opportunity, and I respect that : )

Unfortunately my solutions are, in order;

• spray them with something

• substantially deform the metal

• replace them with something

• do something that someone has yet to suggest

• bi-amp

Maybe a shot of single-malt at this point ... I assume you are working on the 3a Improved speakers.

After that show us a photo of these cretans so we can make an intelligent assessment.

Roger

[ar_pro]

It looks as if these might still be available:

http://www.jvbelectronics.com/

[RoyC]

6 hours ago, TimmyTonga said:

I clean them and test them and the impedance runs smoothly from 0 -16 ohms as I turn. Then I put them in a cabinet and they are immediately intermittent. I mean immediately. Am I doing something stupid? Perhaps I need to bend the wiper more, because if I press gently on the black knob, contact is fine again.....

Any enlightenement out there?

Getting despondent and eyeing up L-pads.....

Tim

Tim,

Post a photo or two of your pot disks and wipers. It isn't uncommon to have drop-outs even though a meter shows a relatively smooth transition from minimum to maximum. Bending the wipers is not likely to improve things if there are any pits or irregularities on the disk or a pinhole in the wiper.

Some pot refurbishment tips:

-The resistor coil is not typically the cause of pot issues. It can be damaged and/or its resistance value can be altered if it is cleaned with something abrasive

-As mentioned above, the wiper tips can have pinholes due to corrosion. Hold it up to a light to inspect it after cleaning.

-Cleaning solvents, including Deoxit, alone are seldom lasting remedies without some kind of abrasive cleaning of the disk and wiper.

-Some pots will suffer corrosion under the rivets of the solder posts, and no amount of surface cleaning will work. These pots should be tossed. This, however, is not usually the cause of an intermittent pot.

There is no reason to persist with pots if they require extreme cleaning, or if they have any drop-outs at all. The old pots do not "sound" better or offer any other advantages over properly implemented L-pads other than visual "authenticity". When the AR-3a Limited was introduced around 1990 it was designed around conventional 15 watt 8 ohm L-pads. (Hey Roger, you knew what I would say if I jumped in here. :))

The switch posted above by ar_pro or new Ohmmite pots can certainly be used as well...but at a significantly higher cost.

Roy

[RoyC]

4 hours ago, onplane said:

I gave up on pots 8 years ago. I bypass the tweeter pot completely and use a padding resistor for the mid driver. This puts the mid pretty much in balance with the tweeter, but way behind the woofer.

I then bi-amp and apply more power to the mids/tweeter to bring them back in balance with the woofer.

Notice that I still have pots, but they are called volume controls and they don't corrode!

Regards,
Jerry

Jerry's baaaaackkk! Old sermon in a number of recent threads for a somewhat new audience?

Where have you been?

Roy

[xpat]

I was ready to put out a post titled "Those Dreaded Pots".  However, I saw your post and thought I'd comment on my recent experience. 

I cleaned the pots on my AR-5s about 5 years ago.  Over the past few months, the mid range and tweeters have been dropping out and driving me nuts.  I decided it was time for surgery again, so I removed the pots from both speakers.  I took 220 grit sandpaper and polished the spring (resistor),  lightly sanding in a perpendicular fashion.  I also sanded the middle of the pot, the two copper lugs that hold the spring, and the "bump" on the wiper - being careful not to bend it.  The pots were then blasted with compressed air, and all contacts coated with dielectric grease - the stuff used on the boots of spark plug wires.  The pots tested fine with a  0-16 ohm reading.  Reassembled everything and the speakers sound great.  It has only been two weeks but I'm very happy with the results.  Listened to a little Brahms, Herb Alpert and Iron Butterfly tonight.  It's amazing what great sound the AR5's can produce for their size. 

(FYI, I removed the pots from my AR-6s a few years ago and replaced them with L-Pads.  I cleaned the pots in the fashion mentioned above and put them in storage.  I tested them and they still are working giving smooth 0-16 ohm readings. I'll keep track of how long the "fix" lasts in the AR5s which are used almost daily.)

 

[onplane]

3 hours ago, RoyC said:

Jerry's baaaaackkk! Old sermon in a number of recent threads for a somewhat new audience?

Where have you been?

Roy

Hi, Roy!

Where have I been ... in one word .... boating!   I bought a 40 foot cruiser and it has consumed much of my time. Tons of reading and lots of upgrades.

Anyhow, my 30 year old amp died (the one driving my TSW's).  So I had to get a new amp and posted here in a thread on an "economical" solution for 4 ohm speakers. The real neat thing about the amp I found is it has 4 full range amps in a single package rated at 100 wpc 4 ohms.  Naturally, with 4 amps I am now bi-amping my TSW's and doing so using just three terminals.

So how have you been, Roy?  I see that many of the old suppliers have disappeared.

BTW, the tweeters on my 3a's are still working just fine after all these years.  I know!  I can't believe it either!

Regards,

Jerry 

 

[RoyC]

25 minutes ago, onplane said:

Hi, Roy!

Where have I been ... in one word .... boating!   I bought a 40 foot cruiser and it has consumed much of my time. Tons of reading and lots of upgrades.

Anyhow, my 30 year old amp died (the one driving my TSW's).  So I had to get a new amp and posted here in a thread on an "economical" solution for 4 ohm speakers. The real neat thing about the amp I found is it has 4 full range amps in a single package rated at 100 wpc 4 ohms.  Naturally, with 4 amps I am now bi-amping my TSW's and doing so using just three terminals.

So how have you been, Roy?  I see that many of the old suppliers have disappeared.

BTW, the tweeters on my 3a's are still working just fine after all these years.  I know!  I can't believe it either!

Regards,

Jerry 

 

So you're a sailor as well as a multi-amp maniac. Glad all is well. I did see your "4 amp" amp thread. 

It is getting more challenging to find worthy parts and restoration candidates these days, but as you can see there are some very resourceful and knowledgeable folks still hanging out round here. I'm still at it as well, but getting tired of moving these boat anchors around (that's sailor talk).

Don't want to hijack TIm's thread...

Roy

[DavidDru]

Forget the pots, use Lpads.  Once you put the old knobs back on them, you never know the difference.  I too left it out of the tweeter circuit.

Now for Jerry, welcome back, but the question I have is how do you listen to music on that cruiser of yours?  Did you rig up a nice stereo on there or is that too much power?

[owlsplace]

9 hours ago, RoyC said:

my 30 year old amp died (the one driving my TSW's).

Jerry,

I don't think four amps are enough for TSW's ... really need a 1/3 octave eq, active xover and one amp per driver to tame those provisional fringe models ...

Back to the OP, no one mentioned Ohmite or similar variable resistors so I will. It all depends on your pocket book and how attached you are to AR's original design. It as all been done by someone else at this point in time so there is nothing new here.

18 hours ago, genek said:

I greased the pots in my 3a's with DeoxIT FaderGrease, which, IIRC from the MSDS is lithium with some "secret sauce" ingredients that Caig claims enhances conductivity. Haven't had any problems with them so far.

Bending the spring wipers might help with contact for a while, but the additional tension won't last unless you substantially deform the metal. 

I'll try some.

14 hours ago, ar_pro said:

It looks as if these might still be available:

http://www.jvbelectronics.com/

Perhaps the ultimate A/P replacement but a little pricey if I remember correctly. Here is the ToO: http://www.jvbelectronics.com/theory.pdf

Roger

 

[TimmyTonga]

Thanks to all for the input. I'm not dead set against using L-pads, but if other people have got their pots to behave properly I dont' see why I shouldn't as well. Roy, yes, I always check the wiper tips and there is usually some 'pitting', which I sand flat. 

The reason I wonder whether wipers lose some of their springy mojo after a while is because two that I bought refurbed from Vintage-AR had wipers that were exerting more pressure on the resistor wire than any of mine. Much more. Whether Larry indulged in some serious metal-bending, or they just happened to be in good shape I couldn't say; interesting though that his shafts were plastic and mine were metal, so his were clearly older than mine, which is a bit counter-intuitive.

will post a photo or two tomorrow, but may consider shelling out £20 for ar_pro's FaderGrease as the next step.

£20!?! I could buy an L-pad for that......

T

[RoyC]

48 minutes ago, TimmyTonga said:

Thanks to all for the input. I'm not dead set against using L-pads, but if other people have got their pots to behave properly I dont' see why I shouldn't as well. Roy, yes, I always check the wiper tips and there is usually some 'pitting', which I sand flat. 

The reason I wonder whether wipers lose some of their springy mojo after a while is because two that I bought refurbed from Vintage-AR had wipers that were exerting more pressure on the resistor wire than any of mine. Much more. Whether Larry indulged in some serious metal-bending, or they just happened to be in good shape I couldn't say; interesting though that his shafts were plastic and mine were metal, so his were clearly older than mine, which is a bit counter-intuitive.

will post a photo or two tomorrow, but may consider shelling out £20 for ar_pro's FaderGrease as the next step.

£20!?! I could buy an L-pad for that......

T

So try bending the wiper a bit! Larry's refurbished pots are not set to a tension specification, but he will bend it as necessary to ensure good contact. Some wipers will lose some tension as a result of the previous user pushing on it as it corrodes. Later pots with metal shafts usually have a second spring shaped like the wiper. If yours is missing, it could account for some loss of tension.

If there is actually "pitting" on the wiper tip to begin with, it is not thick enough to handle much in the way of sanding without developing a tiny hole.

If you are still getting drop-outs after physically cleaning an old AR pot, fader grease and other treatments are a waste of time and money...and any improvement will be temporary.

Roy

 

[RoyC]

1 hour ago, owlsplace said:

Back to the OP, no one mentioned Ohmite or similar variable resistors...
Roger

 

Yes they did...

Roy

[owlsplace]

5 hours ago, TimmyTonga said:

Thanks to all for the input. I'm not dead set against using L-pads,...

will post a photo or two tomorrow, but may consider shelling out £20 for ar_pro's FaderGrease as the next step.

£20!?! I could buy an L-pad for that......

Well, that seems pricey for one pad. Here is a 50w pad for half that: https://www.amazon.com/Parts-Express-Speaker-L-Pad-Attenuator/dp/B0002KR1FU%3FSubscriptionId%3DAKIAILSHYYTFIVPWUY6Q%26tag%3Dduckduckgo-ffcm-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB0002KR1FU

I don't think these fit into the allocated space on the Classics -- 15w are typically used. Ask RoyC what the appropriate shaft length would be.

4 hours ago, RoyC said:

Yes they did...

Roy

Missed that one ...

Roger

[onplane]

6 hours ago, DavidDru said:

Now for Jerry, welcome back, but the question I have is how do you listen to music on that cruiser of yours?  Did you rig up a nice stereo on there or is that too much power?

Actually the boat came from the factory with a German sound system and for the life of me, I can't remember the name. In any event, I never use it. Instead, I have a 2.1 system in the master stateroom that I listen to all of the time. It's not even mid fi, but I can't turn the volume up because of my neighbors at the yacht club. Boats aren't insulated with sound absorbing materials like houses.  All my boating neighbors go to bed early and get up early .... boooring!

On the other hand, My neighbors are quiet and never wake me when they get up. I wish I could say the same about the stupid fishermen. Now the commercial fishermen across the river start revving their engines around 6:00am! By 6:20 they head out ... fishing! Idiots!

[ra.ra]

TT, this is the 15W L-pad that works well in old AR's, 3/8" shaft installs easily and ensures shaft from protruding beyond face of rear cabinet panel.

https://www.amazon.com/L-Pad-15W-Mono-Shaft-Ohm/dp/B0002KR1IW

This nearly identical product is available in the UK, except I believe this one is the long shaft version, which could prove to be annoying. Try to find the shorter shaft variety in your regional market if the restoration of original pots does not work out.

http://www.bluearan.co.uk/index.php?id=MON120610&browsemode=manufacturer

[dxho]

5 hours ago, TimmyTonga said:

Thanks to all for the input. I'm not dead set against using L-pads, but if other people have got their pots to behave properly I dont' see why I shouldn't as well.

T

It is possible to prolong a pot's life by replacing the center disc with a brass washer
and screw/nut, such as Brass Center Hole Round Disc - 14mm.

[ra.ra]

I have no experience with this, but this Korean site seems to offer new wipers and contact discs for old A-P pots.  

http://baenadeul.blogspot.com/2014/11/this-component-is-contact-point-plate.html

[GD70]

1 hour ago, ra.ra said:

TT, this is the 15W L-pad that works well in old AR's, 3/8" shaft installs easily and ensures shaft from protruding beyond face of rear cabinet panel.

https://www.amazon.com/L-Pad-15W-Mono-Shaft-Ohm/dp/B0002KR1IW

This nearly identical product is available in the UK, except I believe this one is the long shaft version, which could prove to be annoying. Try to find the shorter shaft variety in your regional market if the restoration of original pots does not work out.

http://www.bluearan.co.uk/index.php?id=MON120610&browsemode=manufacturer

 

1 hour ago, ra.ra said:

TT, this is the 15W L-pad that works well in old AR's, 3/8" shaft installs easily and ensures shaft from protruding beyond face of rear cabinet panel.

https://www.amazon.com/L-Pad-15W-Mono-Shaft-Ohm/dp/B0002KR1IW

This nearly identical product is available in the UK, except I believe this one is the long shaft version, which could prove to be annoying. Try to find the shorter shaft variety in your regional market if the restoration of original pots does not work out.

http://www.bluearan.co.uk/index.php?id=MON120610&browsemode=manufacturer

Hi Robert!

I bought the exact pots from PE when I restored a set of 2As. After I was set straight here regarding the correct wire connections, they worked perfectly.

Also, thanks for posting that link to the Koren rebuild parts. I had seen that a few years ago, and could not find it again. Curious if it works well.

Glenn

[ra.ra]

Hi Glenn ....... I've enjoyed seeing your recent thread on your "new" AR-3's as they've come back to life - -  terrific work, as always.

I had seen the link before as well, but it occurred to me that I had not ever seen it mentioned in this forum regarding A-P pot restoration. Like dxho has stated above, the pitted disc can probably be replaced with a few different solutions, but this Korean link is the only time I've heard of the production of new metal wipers, which is just as often the problematic culprit.