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AR-3a Rebuild Part 2: What capacitors do I need?

mhjmhjones

mhjmhjones

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Part 1 is here if you want to follow along: http://audiokarma.org/forums/index.php?threads/ar-3a-rebuild-part-1-do-these-woofers-look-ok.748778/

I disassembled the speakers yesterday and cleaned the pots per these instructions: http://audiokarma.org/forums/index....storation-guide-very-long-with-photos.306818/

And here is what I found inside:
M2m7uKX.jpg

LG3B2S4.jpg


I am following the advice of many on here and want to replace the caps. I have never bought or installed caps in my life. I watched a couple youtube videos on what capacitors are, but that's it. These instructions: (http://www.classicspeakerpages.net/...ing_the_ar-3a/restoring_the_ar-3a_full_pd.pdf) state on pages 10 and 16 that the capacitors in my speakers were 6µF-50V and a dual 150µF/50µF (unknown voltage).

On partsexpress.com (http://www.parts-express.com/cat/non-polarized-electrolytic-capacitors/1385), I found caps that are 6.8µF-100V, 150µF-100V, and a 50µF-100V. Are these the right caps I need to order? Does anyone have a link on instructions on how to do this installation? Internet and youtube searches have produced little so far. I think I especially need help on the properly connecting the polarity of the new caps and replacing the "big box" with the two new caps - I don't know how to wire something "in series".

Also, the classic speaker pages guide discusses adding new resistors and inductors (pages 12, 15&16). Does anyone have thoughts on this? I want to do this project right, but I'd also like to lessen the chances of me screwing something up by keeping everything as simple as possible.

Thank you all in advance! Happy New Year!
 
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mhjmhjones said:
Part 1 is here if you want to follow along: http://audiokarma.org/forums/index.php?threads/ar-3a-rebuild-part-1-do-these-woofers-look-ok.748778/

I disassembled the speakers yesterday and cleaned the pots per these instructions: http://audiokarma.org/forums/index....storation-guide-very-long-with-photos.306818/

And here is what I found inside:
M2m7uKX.jpg

LG3B2S4.jpg


I am following the advice of many on here and want to replace the caps. I have never bought or installed caps in my life. I watched a couple youtube videos on what capacitors are, but that's it. These instructions: (http://www.classicspeakerpages.net/...ing_the_ar-3a/restoring_the_ar-3a_full_pd.pdf) state on pages 10 and 16 that the capacitors in my speakers were 6µF-50V and a dual 150µF/50µF (unknown voltage).

On partsexpress.com (http://www.parts-express.com/cat/non-polarized-electrolytic-capacitors/1385), I found caps that are 6.8µF-100V, 150µF-100V, and a 50µF-100V. Are these the right caps I need to order? Does anyone have a link on instructions on how to do this installation? Internet and youtube searches have produced little so far. I think I especially need help on the properly connecting the polarity of the new caps and replacing the "big box" with the two new caps - I don't know how to wire something "in series".

Also, the classic speaker pages guide discusses adding new resistors and inductors (pages 12, 15&16). Does anyone have thoughts on this? I want to do this project right, but I'd also like to lessen the chances of me screwing something up by keeping everything as simple as possible.

Thank you all in advance! Happy New Year!
Click to expand...
Inductors almost never need to be replaced unless there's obvious damage, same with resistors. In all my recap jobs, I've never had to replace a single one, only caps.
If you look at page 10 in the 3a restoration guide, yours appears to be the earlier version, 1967-69. The cap values listed, 3 for each speaker are what you need to order.
Glenn
 
GD70 said:
Inductors almost never need to be replaced unless there's obvious damage, same with resistors. In all my recap jobs, I've never had to replace a single one, only caps.
If you look at page 10 in the 3a restoration guide, yours appears to be the earlier version, 1967-69. The cap values listed, 3 for each speaker are what you need to order.
Glenn
Click to expand...
Thanks Glenn. Parts-express doesn't have a 6µF-50V. They have a non-polarized electrolytic capacitor that is 6.8µF-100V - would that be ok or does it have to be an exact match? Also, the 50µF and 150µF non-polarized electrolytic caps they sell are both 100V also. Do you know if those would work?

Edit: here are links to what I think I need:
http://www.parts-express.com/68uf-100v-electrolytic-non-polarized-crossover-capacitor--027-336
http://www.parts-express.com/50uf-100v-electrolytic-non-polarized-crossover-capacitor--027-354
http://www.parts-express.com/150uf-100v-electrolytic-non-polarized-crossover-capacitor--027-364
 
Last edited:
mhjmhjones said:
Thanks Glenn. Parts-express doesn't have a 6µF-50V. They have a non-polarized electrolytic capacitor that is 6.8µF-100V - would that be ok or does it have to be an exact match? Also, the 50µF and 150µF non-polarized electrolytic caps they sell are both 100V also. Do you know if those would work?

Edit: here are links to what I think I need:
http://www.parts-express.com/68uf-100v-electrolytic-non-polarized-crossover-capacitor--027-336
http://www.parts-express.com/50uf-100v-electrolytic-non-polarized-crossover-capacitor--027-354
http://www.parts-express.com/150uf-100v-electrolytic-non-polarized-crossover-capacitor--027-364
Click to expand...
Higher voltages are fine. Almost all of the caps I've used are 250V. It's the cap value that's important. You can make a 6uf cap with two 3uf caps tied together, or any combination to equal 6uf's.
 
Cap order has been placed! Thanks to all. If anyone know where I can find instructions on instilling/replacing the old caps, I'd appreciate that!
 
mhjmhjones said:
Caps came today, so I know what I'll be doing this weekend! That's right - watching YouTube videos on wiring caps in speakers.
Click to expand...
It's very easy to do, just check your connections multiple times and test them before committing to solder.
 
GD70 said:
It's very easy to do, just check your connections multiple times and test them before committing to solder.
Click to expand...

Understood. The difficult part for me is going to be figuring out which colored wire gets attached to which end of the caps. And what to do with the three wires going into the big box cap - (i.e. how do I connect those three wires to two new replacement caps).
 
mhjmhjones said:
Understood. The difficult part for me is going to be figuring out which colored wire gets attached to which end of the caps. And what to do with the three wires going into the big box cap - (i.e. how do I connect those three wires to two new replacement caps).
Click to expand...
Caps are non polar, it doesn't matter.
 
take multiple pics before snipping anything! adjust wires to view their absolute connection point before taking pics and I generally do one pot at a time, before snipping wires on second. if all else fails, post pics and we will help you! many approaches for "mounting" the new caps, some will mount on top of wax block, I remove block and use a generous blob of "goop" to imbed and secure to xover board.
 
I am late to this thread but I would have recommended using a nonpolar film cap for the 6.8 instead of an NPE. Film caps get rather large at higher values so they're not so great for the big ones, but they will usually fit fine for anything less than 15 uf. The tweeter cap is in the tweeter signal path so the highest quality is a good idea. NPE will work though, try it out and see how you like it. You can always upgrade.
 
toxcrusadr said:
I am late to this thread but I would have recommended using a nonpolar film cap for the 6.8 instead of an NPE. Film caps get rather large at higher values so they're not so great for the big ones, but they will usually fit fine for anything less than 15 uf. The tweeter cap is in the tweeter signal path so the highest quality is a good idea. NPE will work though, try it out and see how you like it. You can always upgrade.
Click to expand...

This is the cap I bought: http://www.parts-express.com/dayton...=1010X497171X44406315914ca94ffce7be526a7d818d

So I need to figure out which end of the cap gets the blue wire and which end gets the green wire! And I used to have that Delicious Vinyl T-shirt back in probably the late 80s?
 

All caps are? Two of the caps I bought are listed as non-polar. The other cap is a Dayton that I need to look up.
 
Hi all,
my Technics SB-A13 3-way speakers are acting strange, at lower volumes the tweeter won't work, unless I increase the volume. Once, increased the volume and lowered back, they work fine.
I suspect the capacitors are dying...any thoughts?

The capacitors that I observed, have unusual marking "50Y1R5K" and also NP 85°C 9305 M07, I tried searching the web to identify what that means so I could order replacement, but cannot find any relevant info except of NP=non polar and obvious 85 deg. Celsius. Any suggestions are welcome!
 
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