9 replies to this topic

[Jonas]

Hello,
A few weeks ago I made my first experience with vintage speaker replacing the foam surrounds of some HECO speakers from the 70s. It was fun and the speakers sound pretty good now.
Last week I found a pair of AR-3 speakers in my grandmother's basement. When connected to an amp one of them is completely silent, but the woofer of the other one is working. I followed the 3a restoration guide for removing grille, woofer and stuffing. I suppose the next step would be to remove and clean the pots and exchange the capacitors. I will attempt to remove the pots as described for the 3a series tomorrow but I am worried that the 3 series differs regarding the capacitors. I have attached pictures of the speakers and the internal wiring below. I am still new to this hobby so if anyone could give me advice how to proceed I would be really grateful.
Many thanks,
Jonas

[Carlspeak]

Hello,
A few weeks ago I made my first experience with vintage speaker replacing the foam surrounds of some HECO speakers from the 70s. It was fun and the speakers sound pretty good now.
Last week I found a pair of AR-3 speakers in my grandmother's basement. When connected to an amp one of them is completely silent, but the woofer of the other one is working. I followed the 3a restoration guide for removing grille, woofer and stuffing. I suppose the next step would be to remove and clean the pots and exchange the capacitors. I will attempt to remove the pots as described for the 3a series tomorrow but I am worried that the 3 series differs regarding the capacitors. I have attached pictures of the speakers and the internal wiring below. I am still new to this hobby so if anyone could give me advice how to proceed I would be really grateful.
Many thanks,
Jonas

Visit the link below and download the .pdf file. It shows 3 different schematics for the AR3. They differ depending on the speaker serial number. Hopefully, yours has readable serial numbers. If not, You have to peel off the inductor and look under it at the printing on the capacitor located there to find the uF values it has. Just order some film caps with the same value, cut the 3 wires close to the old cap (you can leave it in there if you want) and connect them to the two new caps. One of the 3 wires is a common, so that one attachs to the one end of the twisted pair of new caps and then attach the other two wires to the other ends of the appropriate new caps. Solder your connections and wire tie down and/or hot glue down the new caps.

[Jonas]

Visit the link below and download the .pdf file. It shows 3 different schematics for the AR3. They differ depending on the speaker serial number. Hopefully, yours has readable serial numbers. If not, You have to peel off the inductor and look under it at the printing on the capacitor located there to find the uF values it has. Just order some film caps with the same value, cut the 3 wires close to the old cap (you can leave it in there if you want) and connect them to the two new caps. One of the 3 wires is a common, so that one attachs to the one end of the twisted pair of new caps and then attach the other two wires to the other ends of the appropriate new caps. Solder your connections and wire tie down and/or hot glue down the new caps.

Thanks for the reply. Which link do you mean? I have removed the pots, which were surprisingly uncorroded. Unfortunately I cannot find a serial number (where would I normally find them?). Then I removed the inductor and found the following printed on the underside of the capacitor:

Green: 24 mfd. 50 V. D. C.
Black: 6 mfd. 50 V. D. C.
Blue: Common
(see picture below)

I guess the "m" is actually "u" as in micro. So I have to buy a 24 uF and a 6 uF capacitor, solder the green cable to the 24 uF one, the black one to the 6 uF one and the blue one to both?
I was also wondering why there is only a single inductor coil for the woofer and nothing like it for the mid and high. Sorry for this silly question, still learning about speakers. I also measured the resistance between all combinations of the three cables leading to the mid and high. To my surprise, in addition to the expected ~2.6 Ohm resistance between the common and either of the other cables there is low (5.6 Ohm) resistance between the two non-common cables. Does that mean there is a short somewhere?
Thanks,
Jonas

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[Carlspeak]

Attach the blue wire to the twisted together ends of the 6 and 24 film caps. The schematics won't be of much help if you don't know the serial numbers.

The single inductor coil on the woofer is normal. In the early days, AR commonly built their speakers with 1st order elect. xovers.

The 5.6 ohm resistance is okay.

Just clean the pots, install the new caps and re-install the inductor coil and stuffing and you could be ready to go.

[Jonas]

Great, any recommendations regarding the capacitors? So there is supposed to be an electrical connection between the high and mid-range speakers (with the wires desoldered from the pots)? Should I include any resistors to compensate for the modern capacitors as suggested in the 3a restoration guide?

[michiganpat]

Great, any recommendations regarding the capacitors? So there is supposed to be an electrical connection between the high and mid-range speakers (with the wires desoldered from the pots)? Should I include any resistors to compensate for the modern capacitors as suggested in the 3a restoration guide?

erse pulsex would be my choice

http://meniscusaudio.com/capacitors-pulsex-polypropylene-c-101_104.html

use a 5.6 or 6.2uF for the 6uf, and 2 12's paralleled together (or a 20 and a 3.9uf) for the 24....

no, I wouldn't bother with the added resistors

[Carlspeak]

Great, any recommendations regarding the capacitors? So there is supposed to be an electrical connection between the high and mid-range speakers (with the wires desoldered from the pots)? Should I include any resistors to compensate for the modern capacitors as suggested in the 3a restoration guide?

Erse also sells 6.0 caps. Daytons are a popular choice. Solen's were once the popular choice, but they're getting a bad rap lately. Madisound sells surplus film caps. You may find something there.

With regard to your wiring question, perhaps you do need to visit the schematics. Here is the link I forgot to include in my previous post.
http://www.classicspeakerpages.net/library/acoustic_research/original_models_1954-1974/original_models_schematicss/thoughts_on_ar-3_schematics/

No, no resistors are needed.

[Jonas]

Ok, I have replaced the capacitors with Mundorf PP film capacitors (2x12 uF, 1x5.6 uF), cleaned the potentiometers and rewired everything. Both speakers are working now, however I hear almost exclusively the woofer. Both mid- and high-range are extremely quiet even with the potentiometers turned to max (with the woofer disconnected I have to move close to the speaker to hear anything. Is that normal? Any ideas how to troubleshoot. I would like to circumvent the potentiometers to check whether they are the culprits but I have no clue how to do that. Could someone tell me what to connect to what?
Many thanks,
Jonas

[Carlspeak]

Ok, I have replaced the capacitors with Mundorf PP film capacitors (2x12 uF, 1x5.6 uF), cleaned the potentiometers and rewired everything. Both speakers are working now, however I hear almost exclusively the woofer. Both mid- and high-range are extremely quiet even with the potentiometers turned to max (with the woofer disconnected I have to move close to the speaker to hear anything. Is that normal? Any ideas how to troubleshoot. I would like to circumvent the potentiometers to check whether they are the culprits but I have no clue how to do that. Could someone tell me what to connect to what?
Many thanks,
Jonas

If you have a jumper cable with alligator clips, connect the #1 tab to the "B" tab. You should also re-do all the wire connections between the binding posts and the drivers. One or more of them may have deterioriated over time. Re-check the pots to be sure the sheet metal rotors are firmly contacting the stator elements.

[Jonas]

Thanks for the reply. I have measured the resistance between the different tabs on the potentiometers with the following results:
Mid:
"B" to #1: 0.3-16 Ohm
"B" to #2: 2.2-0.3 Ohm

Hi:
"B" to #1: 0.1-16 Ohm
"B" to #2: 1.5-0.2 Ohm

I am not sure but this seems ok. I also tried to measure the resistance to the drivers but this proved to be quite a challenge because of those tiny wires leading to them. Maybe I try running a cable from the potentiometer to the drivers to see whether that makes a difference. Any ideas would be very appreciated.
Thanks,
Jonas

Just tested both speakers playing some Bach. One of them now produces some nice mid and high-range sounds so I know that something is still wrong with the other one. Will continue looking for that loose connection.