Upcoming AR3a project

[ra.ra]

Hey, stubborn Fran, I say "go for it" if you think you can get these pots working well and you enjoy the process of repair and rejuvenation. I know there are many more experienced AR restorers than me here on CSP that hope to never encounter Mr. Aetna or Mr. Pollak ever again, but despite their temperamental moodiness, I kinda like these little ceramic controls, unless they are a total and hopeless mess from the very start. To date, I've not yet rebuilt any speakers with replacement L-pads, and as much as I like those heavy-duty Ohmites, they do add expense and complications to a speaker restoration project, and that's the last thing I need.

It's tough to fully evaluate your soldering efforts in restoring this pot, but I do fully appreciate your industrial spirit. Not unlike your pot sweeper in the first pic, a pot of mine once had a small corroded hole thru the metal tip which I proceeded to fill with a small puddle of solder and then smoothed and polished it to serviceable condition.

Good to hear that you are measuring these pots before re-installing them back in the cabinet - - - that is a crucial step in order to have some degree of confidence in their projected performance. As added insurance to try to delay future corrosion, I first coat my cleaned pots with a silicon spray, and then I add a small amount of dielectric grease for lubrication and further protection.

Even the pot shown in the attachment was brought back to life from the intensive care unit.

[fran604g]

Thanks ra.ra.! I like the encouragement, and I sure don't mind smearing the elbow grease.

That pot of yours gives me some confidence, as it's worse than my worst one, IMO. How long did it/has it continue(d) to work?

Even if my repair only works for a short time, it will have been worth the effort to me. I think it's solid and think it should last close to as long as the original did.

[ra.ra]

This is a pic of that nearly 50 year-old pot before it was removed - - - it came out of a very early AR-4 (see June 1964 date with assembler's personal stamp on inside of cabinet). After clean-up, it measured full range from 0.2 to 16.1 ohms, but because its sister pot had a small dead spot within the sweep (also, I like to work with parts in "pairs"), I opted to replace the pots in the 4's with a pair salvaged from some AR-2a's which had no dead spots. This surgery took place only a few months ago, and although there's no guarantee, I have confidence the old 2a pots will continue to perform well for many years to come. Also, the restored AR-4 pots were so close to testing to spec that I fully expect I'll use them in some other future re-hab project - - - I treated the restoration of these early s/n AR-4's somewhat preciously, which is the only reason I removed the pot with the small dead spot.

[fran604g]

This project is a very good learning experience for me as I have 2 pairs of 4x's here, 1 pair will be restored, the other is beyond help but offered up the pots, one tweet and one woofer. I didn't know much about rejuvenating the pots, but now I think I have the experience to clean them up and make them work. They're next on the agenda.

[danajohnhill]

This is a pot from one of my 3as. I went straight for the Dremel tool with a wire wheel and in a few minutes had it looking like the second photo. Same procedure on all four, and they still work just fine a few years later.

[fran604g]

UPDATE:

I received my new caps the other day and replaced them in both xover's yesterday, stuffed both cabinets and put the woofers back in.

They're looking real nice!

[fran604g]

This is a pot from one of my 3as. I went straight for the Dremel tool with a wire wheel and in a few minutes had it looking like the second photo. Same procedure on all four, and they still work just fine a few years later.

That's good to hear!

I did pretty much the same with 3 out of 4, only 1 of them needed special treatment. I measure all 4 and they are smooth with no dead spots now. All 4 measured ~ 0.5ohms - 15.8ohms before I put them back in circuit.

Not really that much work, IMO.

[fran604g]

My final thoughts:

WOW!

Now I know why so many people love these speakers. Initial impressions are very positive. They are more sensitive than I had anticipated. They sound absolutely beautiful!

The pots perform flawlessly and the latitude that they provide is more than I will need to use.

The left one (SN 3A-04125) is a little brighter than the other (SN 45696) when the pots are all on the "white dot." I think that the newer tweeter and mid range may attribute that.

I balanced the two, by slightly increasing the high and mid output of the all-original (SN - 45696) one and they are perfect to my ears!

I couldn't be happier.

Notice the dead 4x's for stands...temporarily until I get the stands built.

[ra.ra]

Nice work, and it looks like you've got some serious tube power feeding those new speakers.

You can also now say you've got a pair of original AR speaker bases without stretching the truth.

Great job!

[fran604g]

Thanks, ra.ra. I couldn't have done it without a lot of other folks helping me. Very gratifying!

P.S. I figured on using the TAD60 for the 3a's and IMO it was the right decision. I will use the SET for my 604's, though I think that UL is more my cup of tea, so to speak.

[ar_pro]

Wow - Altec 604 and AR-3a.

Yin & Yang!

[fran604g]

Wow - Altec 604 and AR-3a.

Yin & Yang!

Thanks for noticing!

It's going to be tough to decide if there is a favorite between these. 2 such different flavors and textures, yet both so equally amazing, IMHO.

I really am blessed.

[ar_pro]

You are a lucky guy - it's like having both Betty and Veronica available at a moment's notice!

[fran604g]

I posted this in the pinned "Restoring the AR3a" Thread at the top of the page, but didn't get any responses, so I thought I would place the post here, too.

"A comment and question for RoyC, and/or another of the authors.

When I used the "white dot" notation on pg.10 Fig 3.5, I purposely checked my mid range pot at center post B and post #1 and set it at 3.25 ohms as specified, however, I discovered that the pot's locating tab would then be 180degrees from the way it came out of the crossover.

I checked and double checked my reading and the location of the tab in relation to the white arrow on the end of the shaft and it's position in regards to the white dot. I checked my pictures and the picture in Fig. 3.4 and determined that the "White Dot" Settings listed in Fig. 3.5 would cause the pot to be rotated 180 degrees contrary to the picture in Fig. 3.4 (right) shown and, indeed, my own crossover network, also.

When I took the reading from center post B to #2 at 3.25 ohms, the arrow pointed to the white dot when the pot was physically oriented the way it came out of the crossover.

Is it possible that the notation for the mid-range pot should be R,B--->2=3-1/4ohms?

Ironically, there is an old indentation on the Masonite board 180 degrees opposite of the actual location of the tab on the pot I removed. Very odd.

Thoughts?"

[RoyC]

I posted this in the pinned "Restoring the AR3a" Thread at the top of the page, but didn't get any responses, so I thought I would place the post here, too.

"A comment and question for RoyC, and/or another of the authors.

Thoughts?"

Your mid pot is not installed in the correct position. The "old" indentation is most likely the correct one.

Attached is a photo of the pot area of the AR-3a crossover board showing the appropriate location of the pot tab indentations. New indentations are often created after someone reinstalls pots in the wrong position, which can create confusion.

Roy

[genek]

My guess is that at some point in the past the collet nut on the pot loosened and the owner just tightened it without checking position, or incorrectly assumed that the white dot was the midpoint of the pot's travel and realigned it that way before tightening it.

[fran604g]

Your mid pot is not installed in the correct position. The "old" indentation is most likely the correct one.

Attached is a photo of the pot area of the AR-3a crossover board showing the appropriate location of the pot tab indentations. New indentations are often created after someone reinstalls pots in the wrong position, which can create confusion.

Roy

I was thinking that, however, the wiring would then not resemble any of the pictures in the restoration guide showing the location and orientation of the 2 pots. Not to mention both 3a's the way they came apart.

See my above picture and compare it to the one in the restoration guide, they are the same. Wiring, too.

The picture below is as found in the 3a before I took anything out, I had just opened up the pots to assess them. Note the tab location in the right hand pot, which is the one (mid range pot) I am questioning.

[RoyC]

I was thinking that, however, the wiring would then not resemble any of the pictures in the restoration guide showing the location and orientation of the 2 pots. Not to mention both 3a's the way they came apart.

See my above picture and compare it to the one in the restoration guide, they are the same. Wiring, too.

The picture below is as found in the 3a before I took anything out, I had just opened up the pots to assess them. Note the tab location in the right hand pot, which is the one (mid range pot) I am questioning.

Interesting....I have no idea where we got that photo, but it is obviously a crossover board from a very late AR-3a. Maybe AR changed it in later days, and simply used the brown knob to provide the correct positions on the outside of the cabinet. Even if they are not in the same position, the appropriate distance from the white dot, "increase", and "decrease" can be easily set with the pointer of the knobs. This is how I set new replacment L-pads.

The yellow wire connecting the pots is very short, so an adjustment may have been made for an easier fit. (Btw, the quality control of the later back-wired 3a's was not up to the standards of the earlier ones.)

Whatever the reason, the 3a guide and your specimens are showing an exception to the rule in terms of the mid pot tabs.

Roy

[fran604g]

My guess is that at some point in the past the collet nut on the pot loosened and the owner just tightened it without checking position, or incorrectly assumed that the white dot was the midpoint of the pot's travel and realigned it that way before tightening it.

I am convinced that the pots are where they should be, and were in their original locations. The pots that AR used for both drivers are supposed to be identical, correct? If that's the case then by rotating 180 degrees from the other, then the locating tabs would also be 180 degrees from each other, correct?

[RoyC]

I am convinced that the pots are where they should be, and were in their original locations. The pots that AR used for both drivers are supposed to be identical, correct? If that's the case then by rotating 180 degrees from the other, then the locating tabs would also be 180 degrees from each other, correct?

Your tweeter pot is correct, and your mid pot is not typical. It is unfortunate we used that confusing photo in the restoration guide.

Do you have the original brown control knobs? If so, don't worry about the difference. Adjust them accordingly and nobody but you will know.

There is obviously a reason you have an "old" indentation in the appropriate location.

Roy

[fran604g]

Interesting....I have no idea where we got that photo, but it is obviously a crossover board from a very late AR-3a. Maybe AR changed it in later days, and simply used the brown knob to provide the correct positions on the outside of the cabinet. Even if they are not in the same position, the appropriate distance from the white dot, "increase", and "decrease" can be easily set with the pointer of the knobs. This is how I set new replacment L-pads.

The yellow wire connecting the pots is very short, so an adjustment may have been made for an easier fit. (Btw, the quality control of the later back-wired 3a's was not up to the standards of the earlier ones.)

Whatever the reason, the 3a guide and your specimens are showing an exception to the rule in terms of the mid pot tabs.

Roy

Interesting. The guide claims that the crossover that is like mine is from 1967-1969. It's a head scratcher, lol

In any event these 3a's are marvelous, the more I listen to them, the more I appreciate them. I've found that I really don't need to change the pot setting far from their white dots, to fine tune them to my room and system.

Thanks Roy, for all of your time, I really appreciate it.

[RoyC]

Interesting. The guide claims that the crossover that is like mine is from 1967-1969. It's a head scratcher, lol

In any event these 3a's are marvelous, the more I listen to them, the more I appreciate them. I've found that I really don't need to change the pot setting far from their white dots, to fine tune them to my room and system.

Thanks Roy, for all of your time, I really appreciate it.

Just checked out the 3a resto guide photos again. The "1970 to 1975" crossover photo actually shows the later 1974/75 crossover using more modern electrolytic caps. Most AR-3a crossovers (like yours) "looked" like the 1967-1969 crossover into 1973...the primary difference being the woofer inductor (#7 or #9).

The only actual crossover component value "change" was the woofer inductor in 1969 when AR went to the foam surround woofer. Your crossover photo shows the later woofer inductor(#9), so your crossovers would be dated after 1969, and you would have woofers with foam surrounds. No other changes were made to the AR-3a crossover other than type/brand of caps and placement of crossover components. There are no clear dates or documentation of these changes. Your pot placement issue could be in this category.

Roy

[genek]

In this case I would just forget about the indents and use pot resistance to set the orientation of the level controls.

[fran604g]

Just checked out the 3a resto guide photos again. The "1970 to 1975" crossover photo actually shows the later 1974/75 crossover using more modern electrolytic caps. Most AR-3a crossovers (like yours) "looked" like the 1967-1969 crossover into 1973...the primary difference being the woofer inductor (#7 or #9).

The only actual crossover component value "change" was the woofer inductor in 1969 when AR went to the foam surround woofer. Your crossover photo shows the later woofer inductor(#9), so your crossovers would be dated after 1969, and you would have woofers with foam surrounds. No other changes were made to the AR-3a crossover other than type/brand of caps and placement of crossover components. There are no clear dates or documentation of these changes. Your pot placement issue could be in this category.

Roy

Great info, Roy, Thanks! It's very confusing when trying to date the changes and components that were used, I don't know how you keep track.

[fran604g]

In this case I would just forget about the indents and use pot resistance to set the orientation of the level controls.

Thanks genek, I did that.

The level controls when at the white dot setting sound quite nice, I might add. In order for me to "match" the 2 speakers when they were put in system I only had to do a very minor increase to the mid and high of only one of them (the apparently all original one, SN 45696.) They are very balanced, open and image great. The bass is deep and tight, the mids are very accurate, especially with female vocals, and the highs are extended and crisp to my ears, cymbals are clear and sharp.

Very nice!