ADS 710 - Restoration

Almost There · Aug 7, 2014

ADS L710 - Restoration Project

I picked up this pair of ADS 710 off of CL. Very impressive set of speakers. These ADS speakers sound amazing; all the hype is for real. Unfortunately one of the tweeters was blown, but you wouldn't have known from the sound test I conducted while auditioning with the original owner. Fortunately, I remembered the toilet paper tube test on each of the drivers, identified the blown tweet, and was able to negotiate a discount on the asking price.

What is of particular interest is the mystery surrounding the labeling of this pair of ADS.

Crediting AK members jdurbin1 and Blue Shadow: The theory is that these may be a factory sample built as a transition from the 1st version 710 to 2nd version L710. Thus the odd serial number labeling of 710003 and 710010 with no other distinguishing markings other than the ADS grill emblem. The smaller dome tweeter is a 1st version 206-0107, the woofers are 2nd version 206-0325. The grill, emblem and mount details match generation 2. The original owner indicated that no work or replacement of any parts had been made. The odd serial number labeling is a mystery.

Almost There · Aug 7, 2014

The walnut veneer is in very decent shape, with exception of water marks on the tops. But no deep gouges or scratches, and nice clean edges and corners.

Almost There · Aug 7, 2014

The breakdown:

Almost There · Aug 7, 2014

The crossover:

Almost There · Aug 7, 2014

The restoration plan:

1. Find a suitable replacement tweeter. I'd hope to stay with the 206-0107.

2. Replace the 100v 100µF electrolytic capacitors. http://www.parts-express.com/100uf-100v-electrolytic-non-polarized-crossover-capacitor--027-360 UPDATE - Post #20, #21 and #32

3. Replace the binding posts (?) http://www.parts-express.com/binding-post-banana-jack-with-1-thread-2-pair-black-gold--091-1250 UPDATE - Post #22

4. Maybe add a fuse in line with the tweeters (?) http://www.parts-express.com/in-line-agc-fuse-holder--070-609 UPDATE - Post #12 and #21

5. Replace the original fiberglass fill (nasty stuff!) with newer poly-fill (?) http://www.parts-express.com/acousta-stuf-polyfill-speaker-cabinet-damping-material-5-lb-bag--260-330 UPDATE - Post #34

6. Strip, sand, and re-stain the cabinets.

7. Other Suggestions ???? UPDATE - Post #29

Your suggestions and advice are welcomed and encouraged...
Thanks!

relaximus · Aug 7, 2014

Keep 'em coming AT! Looking good so far.

Dave

jdurbin1 · Aug 7, 2014

Can you list the values of the crossover components? We can compare those with the values shown for three different versions of L710 which are in a factory reference document I saw the other day... not much difference between them, but I think they changed at least one inductor value. Was expecting to see a different value for the tweeter first-order capacitor but they appear to use the same value regardless of the tweeter type used (1" or 3/4" ).

Nice thread!

John

Almost There · Aug 7, 2014

A. 100v 100µF
B. 1.5Ω 10% 7W
C. 4.7Ω 5% 5W
D. 4.7 10% 100
E. 10µF/10/100
F. 6.8µF/10/100

jdurbin1 · Aug 7, 2014

Can you add the values stamped on the tops of the inductors? All three versions shown in that schematics document have the same cap & resistor values. Should be four of them... if the stamped value isn't legible, may be able to tell values by color-coding or possibly a part number if one is present.

Thanks,

John

Almost There · Aug 7, 2014

The inductors are 2.5MH, 500MH, 0.18MH and 2.6MH

jdurbin1 · Aug 8, 2014

Ok, that matches the 1st and 2nd version values which were current as of 10/79. That 2.5mh would have been 3.0mH on the final version, which is marked 1982 on the document but likely that version started in 1980 as it's shown that way in the 1980 dealer catalog.

Exception is that 500mH value, suspect that is actually marked in microhenry as the schematic shows 0.5mH value for that one.

Also nice to see that full view of the crossover, which confirms my belief that there were no fuses or other protection in this version. I saw your comment about adding one, but keep in mind you're going to change the tweeter level slightly due to the series resistance of the fuse, and it also slightly changes the filter response for the same reason. It's quite possible that the change in tweeters to the 2016-0107 (or -0117) model came with a slight increase in sensitivity that offset the impact of adding protection to the tweeter circuit. It's also possible that it didn't offset that impact, but that slightly reduced signal and/or change in crossover were complimentary to the smaller dome tweeter.

You might consider using a polyswitch instead of a fuse, which might have less serial resistance than a fuse. ADS did this on a lot of their later models. It's basically a thermal breaker & resets automatically. They can degrade over time & are sometimes found to be causing reduced output to the tweeter in vintage systems but we're talking decades for that to happen, not months or even years. Polyswitches are readily available, just a question of getting the right value and that can probably be derived from looking at the part marking of that part in other ADS crossovers - think there may be a thread on that here on AK somewhere, too.

John

P.S. For reference, here's a link to that crossover schematic document: http://sportsbil.com/ads/xoverschematic.pdf

Almost There · Aug 9, 2014

jdurbin1: Thanks for your input, and the link to the crossover schematic. Very helpful!

A little searching here has revealed that the ADS L810 used a 1.6A 250V fast burn fuse with the 206-0107 tweeter. It is not my intention to alter the original spec on this pair of 710, and I'm hoping to stay with the -0107. I like the idea of a polyswitch, and wondering if these from Mouser would be the right choice: http://www.mouser.com/ProductDetail/TE-Connectivity/LVR075S-1/?qs=%2fha2pyFadug%2fHnrqaibYzBeOZUIk9la%2fTxRVWO4hQd7nKedJ0FBIaw%3d%3d

My other option is to go with the 206-0117 tweeter.

Almost There · Aug 9, 2014

With parts on order, I decided to clean up the cabinets this morning...

Almost There · Aug 9, 2014

They've cleaned up nicely. Maybe a rub with a little Danish oil tomorrow morning and they'll be all set for the electronics.

born2tech · Aug 9, 2014

pretty work

jdurbin1 · Aug 9, 2014

The -0117 and -0107 are more or less interchangeable, it's the original -0100 used in the first version that differs (1" dome vs. the 3/4" of the other two). They didn't ever build the L710 with -0117 as far as I can tell, but that became the replacement part for all of the 3/4" dome tweeter applications after the -0107 was discontinued.

The addition of the fuses on the back panel occurred long after they'd switched from the -0100 to the -0107 tweeter.

Cabinets are looking good!

John

Thocom · Aug 10, 2014

Interesting, perfect timing, I just picked up a pair of these yesterday. They are the 710 (no L).

I just used some Howard's on the cabs, then plugged them in. They sound very very good. Your doing a great job on those!

Thocom · Aug 10, 2014

Here they are after a cleaning. This thread has motivated me to tune these up. Re-cap and check out the rest of the crossovers.

The one thing i don't like about these are the binding posts. I can just barely manage to insert 14 awg bare wire into them.

I see you were going to change out the posts, did you do that yet? Do they drop right in or did you have to modify in any way?

thanks

janikphoto · Aug 10, 2014

Almost There said:
The restoration plan:

2. Replace the 100v 100µF electrolytic capacitors. http://www.parts-express.com/100uf-100v-electrolytic-non-polarized-crossover-capacitor--027-360

Your suggestions and advice are welcomed and encouraged...
Thanks!

Have you thought of going with a different type of cap? I know some of the film ones get pretty expensive, but you've gone through all the trouble to properly rebuild these things...

Almost There · Aug 10, 2014

Thanks for the feedback janikphoto.

I actually have been researching other electrolytic options. For speaker crossovers, it seems like the Elna capacitors get favorable reviews. Still doing my research, and open to suggestions. I'm leaning towards these at the moment: http://www.partsconnexion.com/prod_pdf/elna_rbd.pdf

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