Started my 3A restoration

[LouB]

Hi all,

I have started my restoration of the pair of 3a.

The woofers were foam surround. Rotted, of course.

I sent them to Vintage AR, Quick turnaround, Excellent work and packing.

The crossovers are of the early 5 lb brick variety.

The pots are amazingly free of oxidation. Only needed re-bending the spring leaves to re-establish the pressure and contact on the winding.

If these caps were electrolytic I would replace them without a moments thought, but the dry Industrial Condenser types are giving me pause.

What is the consensus on replacing these?

I have attached a few photos of the caps and Mids / Tweeters.

I searched the previous postings but have not found any definitive information of the foam dot suspension for the tweeters.

They are functional but that foam was applied when I was in my elementary school....

 

Best regards,

 

Lou

[Carlspeak]

Replace the 150, 50 uF wax block with good quality audio grade electrolytics. You won't be disapointed. Replace the wax/paper 6 uF cap with a good quality metalized film cap. Check out parts express. They have a good assortment of brands and prices to choose from. Solen and Dayton of 6.2 uF caps which I think are close enough. Or, you could parallel two 3.0 uF caps for an exact value.

[lARrybody]

I went the exact route Carl describes in the post above with my first set and they turned out great. On the second set I decided to use these big Dayton's and put them back in the box. 

Now I have to figure out the ESR values on these and install them with the proper resisters. I seem to keep getting sidetracked on different projects but will have these finished before Thanksgiving. I suggest reading and re-reading the AR3a restoration guide.

[Carlspeak]

Those paralleled caps will have ESR values in milli-ohms. Suggest if you must add a resistor to duplicate a lytic type of ESR, then about 0.25 to 0.3 ohms would do the job. 

[DavidDru]

Here we go!  Another rebuild thread, and just as the weather is cooling down.

Congrats Lou on the speakers.  We look forward to your progress.  Can you take a shot or two of the speakers and post them?

Oh yeah, Carl's input (along with a few others) is priceless so pay attention.  Between all the been there and done that advice and the AR3a restoration manual, you will have all you need.

[DavidR]

1 hour ago, Carlspeak said:

Those paralleled caps will have ESR values in milli-ohms. Suggest if you must add a resistor to duplicate a lytic type of ESR, then about 0.25 to 0.3 ohms would do the job. 

I'm going to be recapping my AR90s at some point. (sorry, don't mean to be thread hijacking)

Do you place the resistor ahead of the caps or after? Perhaps it doesn't matter.

Would these be a good choice: https://www.madisoundspeakerstore.com/mundorf-10-watt/mundorf-0.33-ohm-metal-oxide-film-resistors/

[Carlspeak]

Those Mundorf resistors will work fine after the caps. 

[DavidR]

Thank you Carl.

Easier to put them there anyway.

 

[ar_pro]

Uh, oh. This thing appears to be contagious.

Here's my empty 3a boxes waiting for their next coat of sealer.

[owlsplace]

16 minutes ago, ar_pro said:

Uh, oh. This thing appears to be contagious.

Here's my empty 3a boxes waiting for their next coat of sealer.

Looks nice -- not a poly-fan though

On 10/17/2016 at 9:42 AM, LouB said:

If these caps were electrolytic I would replace them without a moments thought, but the dry Industrial Condenser types are giving me pause.

What is the consensus on replacing these?

IMHO, replace them ... here are recent measurements on 60s era caps:

Not sure what the original ESR values would be on the old wax caps but the drift and the leakage appear significant.

Roger

[LouB]

Replaced.

The finish was bad.... REALLY BAD.

They were gouged and chipped.

I did the damp rag and clothes iron to raise the grain, sanded, steel wooled and stained. Used minwax Red Chestnut. Replaced the torn grill cloth with 180 count linen. First coat of Johnson wax rubbed on.

[LouB]

a pic of one of them in process;

[ar_pro]

Looks, nice, Lou. Your new grille cloth really sets off the finish. How do you have the panel attached?

My cabinets needed extensive sanding, and I couldn't get a deep enough color from the Howards Walnut Restor, so wound up using Minwax oil stain as well - a quick & light first coat of #231 Gunstock for a hint of orange, and then #2716 Dark Walnut applied about one minute later. All of the remaining stain on the wood surface was buffed off, and I'm pleased with the overall color. The cabinets received their 4th and 5th coats of clear satin poly today, and will receive a final buffing with 3M "0000" synthetic steel wool over the weekend. This is an excellent product, with none of the drawbacks of actual steel wool.

Next, I get to experiment with crossovers & drivers - my Winter Project arrived about two months early.

 

[owlsplace]

9 hours ago, ar_pro said:

Looks, nice, Lou. Your new grille cloth really sets off the finish. How do you have the panel attached?

My cabinets needed extensive sanding, and I couldn't get a deep enough color from the Howards Walnut Restor, so wound up using Minwax oil stain as well - a quick & light first coat of #231 Gunstock for a hint of orange, and then #2716 Dark Walnut applied about one minute later. All of the remaining stain on the wood surface was buffed off, and I'm pleased with the overall color. The cabinets received their 4th and 5th coats of clear satin poly today, and will receive a final buffing with 3M "0000" synthetic steel wool over the weekend. This is an excellent product, with none of the drawbacks of actual steel wool.

Next, I get to experiment with crossovers & drivers - my Winter Project arrived about two months early.

They really do look nice -- actually, I never saw an AR I didn't like.

So I'm always curious how everyone treats AR's idiosyncratic back panel, especially when restoration is not a consideration.

Roger

[LouB]

11 hours ago, ar_pro said:

Looks, nice, Lou. Your new grille cloth really sets off the finish. How do you have the panel attached?

I used the existing grille cloth frames, carefully pried from the glue dots. I used linen material purchased at Jo Ann for the cloth.

It was stapled on two edges, spritzed with water and then lightly stretched and stapled on the other two edges.

Upon seeing the finished project, The Boss pronounced judgement that the contrast was a bit stark.

I noticed that the fabric chosen did have a slight bit of higher frequency attenuation.

Immediately after this, my intrepid sister in law informed me of the existence of this;

http://www.123stitch.com/cgi-perl/itemdetail.pl?item=59-135X
 

DOH! OK, looks like the grille cloths will be replaced again.

For attachment, I used one side sticky Velcro stapled in place to the grille frames and the mounting ledge on the cabinet.

1 hour ago, owlsplace said:

They really do look nice -- actually, I never saw an AR I didn't like.

So I'm always curious how everyone treats AR's idiosyncratic back panel, especially when restoration is not a consideration.

Roger

The back panel of the cabinet remains with the original paperwork attached and the original stain drip in place.

The driver face panel was of course painted black, that was left unmolested.

 

I am wondering whether the woofers might have both been replacements long after the original purchase.

They are foam surround and the existing crossover was the wax / foil type, which I am surmising was typical of the earlier production. No matter, the crossovers are replaced now.

 

Lou 

[owlsplace]

7 hours ago, LouB said:

I am wondering whether the woofers might have both been replacements long after the original purchase.

They are foam surround and the existing crossover was the wax / foil type, which I am surmising was typical of the earlier production...

AR started using foam surrounds in '68 and I think the wax caps made it to Norwood move in '73 -- don't quote me on that though.

Roger

[LouB]

Even after a year with 'em, just can't get over how nice these 3a's sound.

[JKent]

On 10/20/2016 at 9:56 AM, LouB said:

Immediately after this, my intrepid sister in law informed me of the existence of this;

http://www.123stitch.com/cgi-perl/itemdetail.pl?item=59-135X
 

Hi Lou

Nice job on those!

Now, I don't want to be an "I told you so" but when we say "read the AR-3a restoration guide" it's to save folks a lot of headaches. If the Jo-Ann fabric was 180 count as you described that's WAY too tight and probably caused the high frequency attenuation you describe. In the restoration guide, page 17, the 18-count "lambswool" linen from 123 Stitch is described. Maybe your sis-in-law is an AR speaker restorer.

There's also info in there about replacing the caps, dating the woofers etc.

Again--not trying to take a cheap shot. Just want to stress how valuable that restoration guide is.

Enjoy the music!

-Kent

[LouB]

54 minutes ago, JKent said:

Hi Lou

Nice job on those!

Now, I don't want to be an "I told you so" but when we say "read the AR-3a restoration guide" it's to save folks a lot of headaches. If the Jo-Ann fabric was 180 count as you described that's WAY too tight and probably caused the high frequency attenuation you describe. In the restoration guide, page 17, the 18-count "lambswool" linen from 123 Stitch is described. Maybe your sis-in-law is an AR speaker restorer.

There's also info in there about replacing the caps, dating the woofers etc.

Again--not trying to take a cheap shot. Just want to stress how valuable that restoration guide is.

Enjoy the music!

-Kent

No, she's not even an audio geek in any way.

But she does know fabric and where to source it.

Yes, I should'a looked closely at the guide, would have saved me more than a little time.

[lakecat]

Nice job on your redo. It is hectic when doing it for the first time. I had excellent help here and caused me to get the AR fever. Glad they are still sounding good....and glad to see the damp cloth and iron trick worked for ya.....:)