AR90 restore project

[Mr. Weather]

Does anyone have photos of an original AR90 badge showing the front and back?  Im not sure how these are supposed to attach.  The speaker grills have a 1/8" hole where it looks like the badge could be attached with a screw, however the badges on Ebay just have what looks like an adhesive patch on them.  Those could work but I would need to make or buy a small mounting plate of some kind.  So it would help to know what the originals looked like on the back side.

[johnfalc]

1 hour ago, Mr. Weather said:

Does anyone have photos of an original AR90 badge showing the front and back?  Im not sure how these are supposed to attach.  The speaker grills have a 1/8" hole where it looks like the badge could be attached with a screw, however the badges on Ebay just have what looks like an adhesive patch on them.  Those could work but I would need to make or buy a small mounting plate of some kind.  So it would help to know what the originals looked like on the back side.

Here's an album with two photos re original AR-90 badges - one showing the back of the grill and the protrusion of the "pin" of the badge which is secured with a small metal push-on clip.  The other photo just shows the front of the badge.  These are my AR-90s.

https://photos.app.goo.gl/UN7PcZeNrq1YBXZy9

[Mr. Weather]

On 1/17/2023 at 12:36 PM, johnfalc said:

Here's an album with two photos re original AR-90 badges - one showing the back of the grill and the protrusion of the "pin" of the badge which is secured with a small metal push-on clip.

 

Is the badge easily removable to see the whole badge from the side? 

My grill looks just like yours but without the metal pin in the hole, and no metal clip. I may have to wait for an actual set of badges and clips to appear rather than relying on a reproduction.

In other news, I have been testing Danish oil and Odie's polish on different woods.  I have some walnut wood pieces inbound to test those finishes on.  However at this point I think Odie's is best used on some existing finishes as a wax.  Sanded wood I think will be better served by Danish oil in thise case.  Danish oil is a blend of an oil such as linseed, a varnish like polyeurethane, and a solvent like turpentine.  It is thin and runny and soaks into the wood quickly and cures fast compred to pure polyeurethane.

Still listening to the speakers and enjoying them for a while before disassembling them.

I was able to peel a piece of paint off the top of one speaker and I could use that to test on a latex paint remover to see what kind of paint this is, however I think the sanding method is the best option here.

Does anyone have any photos of the bottoms of the AR90s?  Mine are fairly beat up down there, and I suspect I may need to glue on an oak panel to add durability and restore the slight amount of height that may have been lost, but I need to know what the bottoms are supposed to look like.  This would let me attach some feet if they are supposed to have feet.

 

 

 

 

[DavidR]

Those bottoms look like they might have gotten damp. If they are punky you should lightly sand them to get the paint off and use this stuff to harden up the mdf.

https://www.amazon.com/Pacer-Technology-Zap-Finishing-Adhesives/dp/B0006O8ESK/ref=sr_1_3?keywords=Pacer+Technology+(Zap)+Z-Poxy+Finishing+Resin+Adhesives%2C+12+oz&qid=1673991935&sr=8-3

A perfect spray paint to repaint is Rustoleum Universal Satin Black #462466 and is available at Home Depot.

(I hope this post meets John's approval)

[Mr. Weather]

21 minutes ago, DavidR said:

Those bottoms look like they might have gotten damp. If they are punky you should lightly sand them to get the paint off and use this stuff to harden up the mdf.

A perfect spray paint to repaint is Rustoleum Universal Satin Black #462466 and is available at Home Depot.

(I hope this post meets John's approval)

That looks like it would stabilize the MDF pretty well.  Did these speakers originally have feet?

[DavidR]

My first pair of 9s had moisture damage at the bottoms. One had way more than the other. I would not have been able to stabilize the wood and save a pair of 9s without this resin. Thank GD70 (Glenn) who does great wood work on ARs.

I do not think either the 9 or 90s came with feet. Those small holes are for the screws that hold the base plate with the circular hole to the actual base/bottom of the speaker.

IIRC, some have put feet on theirs. Usually the spikes for carpeting.

[Mr. Weather]

I tried Watco Danish oil and Odie's Oil on a new piece of walnut wood sanded to 320 grit.  The other 2 spots on the test board are bare wood. Although the the photos show a slight difference this is due to lighting and the real world difference is not discernable. The Odie's gives a slightly waxy feel, and the Danish oil finish feels more like bare wood.  One of the AR90s has a bare spot in the aftermarket black paint on top so I compared my test board to that.  The test stains look very similar to the AR90. The apparent darker color of the Odie's is due to lighting.  The biggest real world difference is the style of the grain.  I think either finish would work well, but I am inclined to go with the Danish oil.  Probably boiled linseed oil would work perfectly fine too.

Also, one photo shows some flakes of black paint from the top of the speaker sitting in white latex paint remover.  The black paint was not bothered by the paint remover, so I am inclined to think the offending black paint is oil based, not latex.  Does it really matter?  Not sure, but it is what it is.

 

 

 

Edited January 21, 2023 by Mr. Weather
Changed out photos for smaller photos.

[Mr. Weather]

4 minutes ago, DavidR said:

I do not think either the 9 or 90s came with feet. Those small holes are for the screws that hold the base plate with the circular hole to the actual base/bottom of the speaker.

Thanks for the continued information.  You mentioned the cirtular hole and base plate.  What in the world is this design?  It seems really unusual.  This bottom plate seems thin.  I'd love to know more about this part, what it's made from, why it's there, and what care must be taken with it especially if I'm going to be using epoxy resin in the area.

[DavidR]

Here's a thread by me on my first pair of AR9s. Start on page 6. It shows the work I did on the speaker base and what I call the pedestal-base - the piece with the circular hole. The guy I bought these from would drag them out to his backyard garden area and have parties. I actually found a dried up earthworm inside by the lower xover board. The pedestal base seems to be a somewhat soft (on purpose, I think) piece of pressed fiber board of some type. I think the circular hole is to help steady them on carpeted surfaces.

Both the speaker base and pedestal were warped and quite irregular.

 

[Mr. Weather]

9 minutes ago, DavidR said:

Here's a thread by me on my first pair of AR9s. Start on page 6...

 

Great photos. Good thread.  It looks like the bottom most piece is 3/4" MDF.  Mine are lucky to have 1/4" left, maybe 3/8" at the thickest part.  I have to wonder if this MDF piece can just be removed and replaced with a new one. Or is it better to fill and sand it?  The answer might become more obvious when I get the thing disassembled and look at it more inside and out.

[DavidR]

You'll have to see if the screws turn out. The one I have in the pics did not stand straight until I leveled the surfaces. I had to use new screws.

The pedestal base shouldn't be attached with glue, just the (4) screws.

[ar_pro]

3 hours ago, DavidR said:

I think the circular hole is to help steady them on carpeted surfaces.

This sounds exactly right - I can clearly recall circular marks being left in the carpet after AR-9 cabinets were moved.

The fiberboard base always seemed like an afterthought, and it did a poor job of protecting the lower cabinet corners from being dinged when trying to "walk" the speaker across a hard surface, or - heaven forbid - a concrete floor.

If the four screws are removed, the base should come off easily, or with some gentle persuasion if necessary. 

I've had very good results from removing the screws, drilling out the holes, and installing threaded inserts for spiked feet - any sort of cabinet wobble just disappears.

[Mr. Weather]

11 hours ago, DavidR said:

The pedestal base shouldn't be attached with glue, just the (4) screws.

Good information. I should stop asking qurstions until after I've disassembled things.

 

7 hours ago, ar_pro said:

This sounds exactly right - I can clearly recall circular marks being left in the carpet after AR-9 cabinets were moved.

The fiberboard base always seemed like an afterthought, and it did a poor job of protecting the lower cabinet corners from being dinged when trying to "walk" the speaker across a hard surface, or - heaven forbid - a concrete floor.

If the four screws are removed, the base should come off easily, or with some gentle persuasion if necessary. 

I've had very good results from removing the screws, drilling out the holes, and installing threaded inserts for spiked feet - any sort of cabinet wobble just disappears.

I can see how the circular base would work better on carpet by creating more pressure over a smaller area compared to a piece without the cutout.

Is there a single library of technical and related information for restoring this model? Some consolidated resource that covers the well known hurdles with restoring these, either here or somewhere else on the Internet?  It would have data like capactor sources, important bits from the owner's manual such as the reccomended polishes for the walnut veneer, other part numbers and sources, repairing common problems like a damaged base, etc.  It would help folks like me from reinventing the wheel each time

[Mr. Weather]

I started disassemly.  I am labeling all of the parts with the last 3 digits of the serial number of the speaker they came from. (521 and 518).  Probably this makes no difference but couldn't hurt.  The drivers all have the white/pink "Made in USA" part numbers on them.  One indicates it is a "service replacement unit".  The drivers all appear to be stamped with "SFT 8" in black ink.

One woofer screw is wrong: too long, and one size too small.  The original gaskets on the LMR and tweeters appear to be intact.  The woofers will need new gaskets or gasket tape which I have.

The brace above the woofers is stamped with "56181 10"  Is this a date code?  October 1981?

The bottom screws have no heads.  Probably cut of sheared off.  When I get the thing outside and preppred and sealed up, I'll try to pry that off.

The only capacitors I could identify by name are Callins. 

To remove the rear crossover board (the one with the external connections/controls), I assume I pull out the staples that holds it in?

A few photos:

 

 

 

 

 

 

 

 

Edited January 21, 2023 by Mr. Weather
Swapped photos for smaller ones. Removed some photos.

[DavidR]

54 minutes ago, Mr. Weather said:

I started disassemly.  I am labeling all of the parts with the last 3 digits of the serial number of the speaker they came from. (521 and 518).  Probably this makes no difference but couldn't hurt. 

I also keep parts with the respective speaker. Why not.

I did my boards in place but mine are very early production and don't have the board with the resistors. The 6uF cap on the far side was a bitch to get at. Really had to take my time and get my lighting right. Yes, carefully pry the staples out. The boards may also be glued down. The advice I always give myself is have no expectation as to how long anything should take. Take your time and be patient.

[Mr. Weather]

I measured the capacitors in the first speaker using a Fluke 115 multimeter.  The values are shown in an image below.  These are way out of spec.  Three of them did not yield a capacitance measurement but they did pass a continuity test.

Normally I would buy replacements at parts-express.com, but they do not offer a 350 uF.  Does anyone have a reccomendation for something other than parts-express.com?   The 80 uF units are $42 each. 

Also, some of the capacitors have two terminals on top but the items at parts-express are all axial with a wire on each end.  Not sure if this matters or not.

[DavidR]

200uF + 150uF in parallel NPE

That's what I used.

Just think how good they will sound with new caps.

[ar_pro]

Those are surprisingly poor readings.

Did you happen to check your meter against a capacitor that you know to be in spec?

[DavidR]

1 hour ago, ar_pro said:

Those are surprisingly poor readings.

Did you happen to check your meter against a capacitor that you know to be in spec?

I thought so too.

NPE caps need to be checked at 1000Hz. Make sure your meter is on uF and 1,000Hz

You could also try   https://www.partsconnexion.com/capacitors-ele.html  

They have Mundorf ECap and Jantzen. Just make sure they are non-polar.

[Mr. Weather]

18 hours ago, DavidR said:

200uF + 150uF in parallel NPE

Yep, that seems to be a workable combination.  Those 2 values seem to be fairly common.

17 hours ago, ar_pro said:

Those are surprisingly poor readings.

Did you happen to check your meter against a capacitor that you know to be in spec?

Good call. I checked against a known new capacitor and got nothing.  Based on that I'm inclned to think the Fluke 115 is flakey.  Either way, the capacitors are old and should probably be replaced.

16 hours ago, DavidR said:

I thought so too.

NPE caps need to be checked at 1000Hz. Make sure your meter is on uF and 1,000Hz

You could also try   https://www.partsconnexion.com/capacitors-ele.html  

They have Mundorf ECap and Jantzen. Just make sure they are non-polar.

My meter doesn't have settings for frequency as far as I know.  It is auto ranging for farads, but I couldn't get readings in either auto or manual modes with the known good test capacitor or the AR90 capacitors that gave no reading. 

I found this place:

https://www.madisoundspeakerstore.com/solen-capacitors/

They have a great selection of Solen "metallized film, polypropylene, non-polar" capacitors.  But holy cow, the full array is going to cost $214 per speaker, plus shipping   Maybe they will last for a long, long, long time.

Friday I should be able to pull the drivers from the other AR90.  I made some wooden and cardboard panels to fill in the driver holes to help keep dust and debris from getting inside the cabinets.  Then I can get them outside and get the bottom MDF panels off and hopefully work out a plan to restore the bottoms.  I like the epoxy idea of bar clamps and wood blocks to shore up the sides while the epoxy cures.

I need to come up with some way to protect the acoustic blankets and front of the cabinets, without getting in the way of the sides of the cabinet.  Probably painter's tape with a custom made shallow cardboard tray to cover the blanket. 

[Mr. Weather]

Can the screws in the tweeter below be removed safely without risking the tweeter?  They need rust removal and possibly painting, but I don't want to risk the driver.

 

[Stimpy]

Those four screws hold the faceplate and tweeter diaphragm together and in alignment.  If you want to clean them up, only remove one screw at a time, so nothing shifts out of place.

Capacitors can be daunting.  Hard to decide how to replace, and with what?  I used poly for the series values, (4, 6, 24, and 80), and NPE for the rest (8, 30, 40, and 350), to save a little money.  You'll most likely have to bundle 2 caps in parallel, to add up to the needed values.  That's unfortunately a common solution.  Good capacitors can be found at Parts Express, Parts Connexion, Madisound, Meniscus Audio, and Sonic Craft.  Prices vary, so be warned...!

[Mr. Weather]

On 1/20/2023 at 12:45 PM, Stimpy said:

Those four screws hold the faceplate and tweeter diaphragm together and in alignment.  If you want to clean them up, only remove one screw at a time, so nothing shifts out of place.

Makes perfect sense. Thanks.

On 1/20/2023 at 12:45 PM, Stimpy said:

Capacitors can be daunting.  Hard to decide how to replace, and with what? 

Ultimately, in keeping with the original design of the crossover, I'm going to stick with regular NPE capacitors.  I was able to source exact or near exact values from Parts Express and Madisound.

I don't think I'll have to remove any of the crossover boards.  The hardest capacitor to reach is the 6 uF unit on the top of the rear board but I can access it through the woofer hole on the left side.

The Z-Poxy is on order but will take a week to arrive.  I have another test strip of walnut going where I've added an additional coat of Danish oil every 24 hours.  Probably 3 coats is plenty but the test panel has 4 squares so we'll see if there is any benefit to 4 coats.

The weather will be dry, sunny, and slightly cool Sunday so I may haul the cabinets outside and see how the veneer stands up to some careful sanding.  I also have to deal with the bottom panels and the screws with no heads.  Ideally I can remove the MFD around the screws and then use a vice grip to unscrew them.  I have other more forceful methods but will start small.

In a non-related topic, I pulled the trigger on a local pair of "parts only" The Advent Loudspeakers for $60. I will post a thread over on the Advent forum.

 

 

 

 

[johnfalc]

Nice to see the work you're doing - I'm sure you're going to enjoy these when complete.  I also used just NPE caps and find that my AR-90s sound terrific (as do my AR-9s, etc., also recapped with NPEs).

[Mr. Weather]

Great news, the offending black was sanded off gracefully without damage to the veneer.  With a Bosch random orbit, variable speed sander, I started with 220 grit but switched to 150 grit for the bulk of the paint removal.  Then I made a pass with 220 to remove the smallest remaining bits of paint.  I sanded all of the sides, including the factory black area.  I also sanded the large scratches on the back of the cabinet and test painted a corner with black to see if that's going to work, of if I need to sand the whole back before painting it black.  The initial result is that the scratches are pretty deep so I may end up needing to deep sand the whole rear panel.

I also worked on the base:  The base did not have screws, but had small finshing nails.  I was able to remove the original "circle cutout" base (what is left of it) but I'm confused about what was left behind.  You can see the odd round bulge on the bottom.  So what's my move here?  shore up the edges with wood blocks and flood the whole base with epoxy, including the round bulging part?  Then glue on a new solid oak base?  That's what I'm thinking.

It's now occuring to me that the circle is bulging because it was wet and it was not originally like that.

Today I only did one speaker.  The other one is still inside waiting to be sanded.  It is slow work, even with the sander doing the hard part.

I also shot some video of the work today and will throw together a video to document this project after all of the work is done.