where to get replacement pots?

[madwing]

i purchased this pair from here: http://www.surplussales.com/Potentiometers...tsRheost-1.html , item no. (RWA) RP102SK150KK

the second soldering post (at the far end of the sweep) is really insubstantial. i was planning on cutting down the shafts and putting a half-shaft cut on the end (machine shop access), but now i wonder.

i've tried to get in touch with leeds electronics in brooklyn, but they don't answer their phone or return their emails. the skycraft surplus site no longer lists the pots for sale.

so, where are people getting 15 ohm, 25 watt rheostats to replace their originals in ar speakers? any leads would be appreciated.

thanks

madwing

[Carlspeak]

Call AB Tech and see what they have that is a good replacement rheostat. Don't settle for a cheap L-pad. It should be a 15 ohm, 25 watt min. rated rheostat.

If you strike out there, be prepared to spend about $25 each at electronic suppliers. They all list about the same price. Ohmite and Memcor are about the same.

It's all about the music

Carl

Carl's Custom Loudspeakers

[madwing]

so, by and large, the $9 pots are gone, it seems. thanks for the tip, carl. i'll have to see if ab tech has any.

and, in search of "AB Tech" i found the attached list on the internet. it might help someone in search of "electronic parts".

best,

madwing

1881.txt

[dynaco_dan]

Hi there;

Carl did a few write-ups previously regarding the AR pots and has a great deal of experience in that area.

There is surplus Ohmite pots, which unfortunately, have an exposed rear assembly, rather than the AR original Aetna-Pollok metal covered coil/rotor.

There is also a Chinese version pot with also an exposed coil/rotor, built like a tank, very similar to the Ohmite.

These are about $15.00 CDN here in Vancouver from a local elctronics store.

As with every thing else from China, you should be able to obtain them for less money in the USA.

Unfortunately, what is here is stocked in 25 watts, but not the 15 - 16 ohm version, I have asked, and it is made and available.

The Ohmite surplus was made in the USA, and very well made, I must say.

I have with James' help, tried to track down an elusive non-combustible, non-conductive and cheap, I'm looking at a dollar each or less, suitable rear cover.

I have a number of close choices but nothing to write home about, yet.

When I have something that fits the bill you will all read about here.

The Ohmites are stocked by, Allied Electronics for one, I believe, check out Ohmite's website, they have a listing of pot distributors.

These are not cheap, but this is an investment and will not need to be re-done in our lifetime, if done right.

If one is going to change pots, it may be worth the little extra effort to coat the contactor/coil with Caig's Deoxit prior to installing it, for all it's worth.

Automotive suppliers have a special grease/lubricant for such purposes as well.

Just for trivia's sake, the earliest pots, re: AR-2 era, were Clarostat 4 watt 10 ohm wire-wound pots.

These used a complete fine copper wire multiturn coil rather than the usual resista wire with only a dozen or so loops.

[Carlspeak]

Yes, the discounted US made rheostats are scarce as hen's teeth at the moment. I keep checking around but at this point in time around $25 is the going price for well made units. I bought ten at discount from an outfit in Florida about a year ago. They're all gone now. The AR rheostat kits on my web site currently reflect pricing based on the going 'list' price.

Vern is right. The wiper section is exposed on the Ohmite and Memcor pots. However, I get around that by fabricating a simple cover out of wood to keep the fiberglass out of that area..

It's all about the music

Carl

Carl's Custom Loudspeakers

[Guest mdavis]

As a novice, I don't have connections to the big mail-order houses for replacement parts. Can someone list (or direct me to a previous post) of replacement parts (pots and caps) with part numbers from the appropriate supply houses? I'm working on AR-3a's and AR-2X's. Price is not much of an object as long as the specs are correct and the quality is there.

[Carlspeak]

>As a novice, I don't have connections to the big mail-order

>houses for replacement parts. Can someone list (or direct me

>to a previous post) of replacement parts (pots and caps) with

>part numbers from the appropriate supply houses? I'm working

>on AR-3a's and AR-2X's. Price is not much of an object as

>long as the specs are correct and the quality is there.

Try DigiKey.com

The p/n is RHS15RE-ND

It's all about the music

Carl

Carl's Custom Loudspeakers

[stan461]

Digikey is quoting $25 per piece X 4 per pair = $100.00. Plus shipping & handlig. Whoa!

A lot of great ideas are talked about here but few come to fruition.

What happened to this project?

[madwing]

my 4x's are currently rewired to bypass the pot (per onplane's instructions), and they sound fine. i have two refurbished pots coming from vintage-ar on eprey, and might use them here, replacing the current pots; then i'll refurb the original pots, maybe send them to larry to see if he can work his magic on them for a price.

i've not used the pots from surplussales, and have been talking with someone else who got theirs from leeds...just a pain, they're not very available by phone, or email.

[Guest matty g]

>my 4x's are currently rewired to bypass the pot (per

>onplane's instructions), and they sound fine. i have two

>refurbished pots coming from vintage-ar on eprey, and might

>use them here, replacing the current pots; then i'll refurb

>the original pots, maybe send them to larry to see if he can

>work his magic on them for a price.

>

>i've not used the pots from surplussales, and have been

>talking with someone else who got theirs from leeds...just a

>pain, they're not very available by phone, or email.

Hi Madwing -

Just for the record, 4x's sound great with a 3 ohm ceramic resistor wired between the pot and the tweeter lead (leaving the pot wired in as done at the factory). That way you still have the pot resistor in the circuit and the tweeter is slightly dampened. It really knocks down the harshness and lets the tweeter operate just shy of the maximum setting. I've done this on quite a few of the 4x systems and it puts 'em right, no control pot needed.

Hey - did you ever get that 9090? If so...how does it sound?

Take Care

Matt

[onplane]

madwing,

You have a large number of options. Matt thinks the AR's sound too "harsh" with the pots at MAX. He's further tested a number of different options and settled on a solution the works best for him.

I think that's what this hobby is all about ... trying different combinations until we achieve a "sound" that we like AND sharing our results.

madwing, I'd encourage you to do the same. You can easily alter one speaker and then using a mono source compare to the other.

Wherever you end up, however you get there, I'd encouirage you to SHARE what you did and what you heard.

I had a set of those 4x's when in college and I thought they were simply terrific!

Regards,

Jerry

[dynaco_dan]

>i purchased this pair from here:

>http://www.surplussales.com/Potentiometers...tsRheost-1.html

>, item no. (RWA) RP102SK150KK

>

>the second soldering post (at the far end of the sweep) is

>really insubstantial. i was planning on cutting down the

>shafts and putting a half-shaft cut on the end (machine shop

>access), but now i wonder.

>

>i've tried to get in touch with leeds electronics in brooklyn,

>but they don't answer their phone or return their emails. the

>skycraft surplus site no longer lists the pots for sale.

>

>so, where are people getting 15 ohm, 25 watt rheostats to

>replace their originals in ar speakers? any leads would be

>appreciated.

>

>thanks

>madwing

Hi there;

I went to that site and looked at the 15 ohm 25 watt Tru-ohm pot they are offering for $9.00.

It has a 1/4" x 2" long steel shaft, which can be cut down and slotted if need be.

It LOOKS to be physically identical with the Ohmite version, except the shaft length, but the view on their site is not detailed enough.

Your comment of the second soldering post means you were not able to solder any wires to it?

Did you continue to install these pots?

The careful use of a fine hacksaw blade cutting in the shaft in the same direction as the rotor should work out.

Inserting a hacksaw blade in a vice and stroking the shaft back and forth should work also.

Surplus Sales has a 800.244.4567 number for those interested.

I placed an order for 100 of them and there was no message as to being out of stock, etc.

I did not complete that order.

I didn't have any success finding out how many they had in stock.

With more effort maybe someone here can find that information.

If they have an abundance of them, (100's), in stock, I would really appreciate one sample to check out for the rear safety enclosure fit.

I am tracking down rear covers for the Chinese and Ohmite pots.

Thanks to James for his support in this project.

I presently have a physical match for these two, unfortunately they are dimensionaly too far apart to use the same size.

Also the matches I have found are not non-combustible.

The hunt continues, but getting closer.

If I am successful I will post it here.

[Carlspeak]

Vern, don't complete that order. Those surplus pots have only TWO soldering posts and thus won't work for mose AR applications.

I have to eat 6 of these turkeys I bought because I was fooled by their photo into thinking these were the same as the other surplus pots folks like Leeds were selling. They are packaged in a sealed, foil-lined pouch and stamped MIL-R-22A and dated Feb. 1960.

At this point, anybody wanting new pots will have to accept paying top dollar for the 'real deal'.

It's all about the music

Carl

Carl's Custom Loudspeakers

[dynaco_dan]

Hi Carl;

Thank you very much for that update.

My purchase was only to find out the number that they had in stock only at this time.

Perhaps there is other more compatible pots at an attractive price that will come our way soon.

We gain by your experience, Carl, thank you.

It appears that the $23+ plus dollar, Ohmite, and the Chinese ($?)versions are the most accessible, the Ohmite is my preferred of the two.

Has anyone located the Chinese pot, US price un-known, built like a tank, in an electronics store or mailorder house?

[dynaco_dan]

Hi again Carl;

Could you please tell me what would happen if this Tru-Ohm 15 ohm 25 watt w-w pot was inserted into, say, an AR-4X, just for a simple speaker circuit example.

I know that the outer terminal to speaker common would not be connected.

This would still leave an adjustable resistance to the tweeter, 0 -15 ohms.

With only 2 terminals I assume the one side is on the coil and wiper blade is the other.

On a regular pot there is a terminal on each end of the coil and one for the wiper.

Usually one end contact to speaker common, center to tweeter and the other end to capacitor output.

The AR-2 tweeter was wired using only the outer and center terminal connections of a 10 ohm 4.5 watt Clarostat w-w pot.

I do not have an AR-2A crossover handy to see if they also are using only the center and one end terminal, presumably yes, at least with the Clarostat pots.

The AR-2AX later version of crossover that I have has the Aetna-Pollock pots and uses all 3 contacts.

The rear open view of the MicroStatic Tweeter Array speaker photo shows another pot for those tweeters using only the center and one outer terminal, leaving the other outer terminal un-used.

If these two examples, assuming they were instead 15 ohm pots, were to have the empty un-used terminal connected to the speaker common what would happen?

Likewise, if the common connection of the pot in the AR-4X was disconnected, what might happen?

[Carlspeak]

I just got 4 today from Mouser. Ohmite p/n RHS15RE. They are the right ones.

Don't try to order and ship to another addres other than your own. They give you a hassle about it. I was not happy with that portion of the transaction.

It's all about the music

Carl

Carl's Custom Loudspeakers

[Carlspeak]

Attached is a summary page of what's left of the new, full price Ohmite 15 ohm pots. There are 27 left among 4 distributors. The page includes who's selling and their volume pricing.

It's all about the music

Carl

Carl's Custom Loudspeakers

[onplane]

Carl, when you look at the magnitude of corrosion, I'm just wondering whether those of us who solder the wiper lead to the top of the are really safe.

Specifically, have you ever noticed a pot that measures significantly greater than 16 ohms? Naturally, I'm NOT talking about pots that completely open up, but rather if the corrosion impacts those termination points for the resistance wire.

Regards,

Jerry

http://www.classicspeakerpages.net/dc/user_files/2112.jpg

[RoyC]

>Specifically, have you ever noticed a pot that measures

>significantly greater than 16 ohms?

Jerry,

I have measured a large number of pots over the years. Although they typically measure between 15 and 16 ohms, it is not unusual to find them between 16 and 17 ohms...even after cleaning.

Roy

[dynaco_dan]

Hi Roy;

BC Canada is well known for it's extremely large and potent pot crops.

It looks to me that you are cultivating pots, familar ones even, Aetna-Pollock at that.

When are you harvesting them?

What are you doing with those lovely pots, Roy?

It appears that only a few surplus Ohmite pots are available as I read the previous write-ups.

Does that mean they are no longer manufactured?

Does this leave us only with the Chinese pots and the dozen or two Ohmites?

[Carlspeak]

>Hi Roy;

>

>BC Canada is well known for it's extremely large and potent

>pot crops.

>

>It looks to me that you are cultivating pots, familar ones

>even, Aetna-Pollock at that.

>

>When are you harvesting them?

>

>What are you doing with those lovely pots, Roy?

>

>It appears that only a few surplus Ohmite pots are available

>as I read the previous write-ups.

>

>Does that mean they are no longer manufactured?

>

>Does this leave us only with the Chinese pots and the dozen or

>two Ohmites?

>

>

Mamcor makes one that is identical to the Ohmite.

It's all about the music

Carl

Carl's Custom Loudspeakers

[Carlspeak]

>Carl, when you look at the magnitude of corrosion, I'm just

>wondering whether those of us who solder the wiper lead to the

>top of the are really safe.

>

>Specifically, have you ever noticed a pot that measures

>significantly greater than 16 ohms? Naturally, I'm NOT

>talking about pots that completely open up, but rather if the

>corrosion impacts those termination points for the resistance

>wire.

>

>Regards,

>Jerry

>

>

>http://www.classicspeakerpages.net/dc/user_files/2112.jpg

>

If resistance is well beyond the normal 16 ohms max, then I believe your simply measuring the added resistance brought on by the corrosion as shown in your photo.

It's all about the music

Carl

Carl's Custom Loudspeakers

[Carlspeak]

Sorry for the bad attachment guys. It seems word docs don't upload well. Here's a .pdf of the same info.

It's all about the music

Carl

Carl's Custom Loudspeakers

[RoyC]

Hi Vern,

>What are you doing with those lovely pots, Roy?

Most of them belong to pending restorations, and some are just pieces o' pots :-). I had more, but have been sharing them with fellow forum members.

Changing subjects, I had posted the following in another thread, and believe it is worth investigating:

I have recently experimented with modifying the effect of ordinary "8 ohm" l-pads as a possible alternative to the 15-16 ohm potentiometers. It seems that by placing a 24 or 25 ohm resistor across the parallel leg of the l-pad (terminals #1 and #2) or, looked at another way, across the mid/tweeter terminals with l-pads in use, the l-pad appears to electrically "act" like an AR pot. If someone is looking for a quick and inexpensive (albeit non-authentic) way to replace level controls without altering the original sound, it works. Those of you with meters can easily verify this.

The upside is that the AR crossover remains unchanged, and the back of a replacement rheostat does not have to be dealt with (l-pads have covered backs). The only real downside is that the only l-pads that fit the stock crossover board holes, side by side, are the 15 watt variety, thus lowering the power handling ability. With that said, it should be noted that AB Tech's so-called AR replacement "potentiometers", as well as the controls sold on Ebay, are garden variety 15watt 8 ohm l-pads. These are identical to those sold by internet speaker parts suppliers for less than $4 (ie Madisound and Parts Express).

Roy

[onplane]

>

>I have recently experimented with modifying the effect of

>ordinary "8 ohm" l-pads as a possible alternative to

>the 15-16 ohm potentiometers. It seems that by placing a 24 or

>25 ohm resistor across the parallel leg of the l-pad

>(terminals #1 and #2) or, looked at another way, across the

>mid/tweeter terminals with l-pads in use, the l-pad appears to

>electrically "act" like an AR pot.

>

>The upside is that the AR crossover remains unchanged, and the

>back of a replacement rheostat does not have to be dealt with

>(l-pads have covered backs). The only real downside is that

>the only l-pads that fit the stock crossover board holes, side

>by side, are the 15 watt variety, thus lowering the power

>handling ability. With that said, it should be noted that AB

>Tech's so-called AR replacement "potentiometers", as

>well as the controls sold on Ebay, are garden variety 15watt 8

>ohm l-pads. These are identical to those sold by internet

>speaker parts suppliers for less than $4 (ie Madisound and

>Parts Express).

>

>Roy

>

Hi, Roy!

The plot below shows the theoretical value of the L-Pad + 24 ohm shunt vs. a 16 ohm pot.

In short, your solution tracks fairly well when the series resistance is in the range of interest (0.5 to 3 ohms).

As for “lowering the power handling ability”, I don’t think that’s much of an issue. Please remember that the 24 ohm shunt is dividing current with the L-pad. At 1 ohm series resistance, twice as much current is going through the 24 ohm shunt than through the L-Pad shunt.

Regards,

Jerry

http://www.classicspeakerpages.net/dc/user_files/2115.jpg