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PostPosted: Wed Mar 01, 2017 6:14 pm 
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Location: kemptville, ON, CA
I ordered new capacitors for my Heathkit-AS27 (aka Jensen SG-300) speakers

But when I removed the existing capacitors there were two. One matches the 1.8uf size, but the original second one is rather odd. It is 35 MFD 50v , but is 1/4 the size of the new one. I have attached pictures of the original.

Here is the link to the Solen capacitors they recommended as replacements.

1.8uf = PA180 http://solen.ca/products/capacitors/fas ... ene/pa180/
35uf = PA3600 http://solen.ca/products/capacitors/fas ... ne/pa3600/

Before I actually replace them, could someone verify that it is a valid replacement before I damage my 50+ year old vintage speakers ?

Could the original value really be 35 uf instead of 35 MFD ?


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WP_20170301_16_48_59_Pro.jpg
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PostPosted: Wed Mar 01, 2017 6:27 pm 
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35 uf IS 35 MFD. The actual symbol for microfarad (1/1,000,000) is μF, not uf, mainly because most people know where to find the symbol μ on a keyboard. In texts prior to 1960, and on capacitor packages even much more recently, mf or MFD rather than the modern µF frequently represented microfarads. MFD is not an official abbreviation for capacitance though mF is the correct abbreviation for millifarad (1/1,000 of a farad)

A picture of the old one VS the new one would be more useful.


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PostPosted: Wed Mar 01, 2017 8:49 pm 
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Thank you for clarifying that. The old ( black & red ) and the new ( black ) are included.

New Solen ( 34mm D x 48mm L )
Old Nashville electronic ( same diameter as a Sharpie marker)


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WP_20170301_16_48_33_Pro.jpg [ 467.49 KiB | Viewed 1155 times ]
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PostPosted: Wed Mar 01, 2017 9:15 pm 
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There is the reason for the size difference; the new cap is rated at 5X the old cap's voltage spec (250V VS 50V). Over-specing operating voltages can only help in terms of longevity, so if the old ones lasted as long as they did, the new ones should survive your great-grandchildren's kids!


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PostPosted: Wed Mar 01, 2017 9:51 pm 
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Thank you. I feel better about going ahead with the replacement. I am really curious to hear if and what difference in sound there will be.

I have attached a picture of the cabinets they are in.


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PostPosted: Wed Apr 05, 2017 4:57 pm 
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Your original capacitors were non-polarized electrolytic capacitors. You should use the same type. The capacitors you have now aren't rated for the same current and may open up. Your system will also sound brighter because they are better capacitors, but not the way your speakers were originally voiced.

I really like the Solen products, especially these capacitors. However, they aren't the right ones for this job. If you find the speakers sound weird or too bright, going back to the original style capacitors will sort that out completely.

Buy them at Digikey or Mouser electronics off the web. MCM probably carries them as well.

-Chris


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PostPosted: Wed Apr 05, 2017 11:46 pm 
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I redid the caps in my Heathkit AS103 a number of years ago. The speakers are 44 years old this year and are best suited to tube amplifiers.
I chose Solen capacitors as you have and was satisfied with the results. As system components changed or were upgraded I noticed that some of the different DACs I was using on my streamers started sounding too sharp/harsh on some of my music. Always felt that the problem was in the preamp or the streamers but could not put my finger on the problem. Stayed that way for a while until I reanalyzed the whole system and extended my analysis into the speaker crossovers themselves focusing on the tweeter and mid-range capacitors. I had in my readings come across a comment from another diy person who suggested that Solens were sometimes not a good match for mid range.
I changed those Solen out for Clarity caps and the issue has been resolved for my ears. The Clarity are in my price range.
Here is a link for you with more background information. Hope it helps. My comment supports what the previous poster has observed about using the appropriate caps for the job.

https://www.madisoundspeakerstore.com/r ... e-speakers


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PostPosted: Thu Apr 06, 2017 1:30 am 
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Thanks, I will look into the advice.

Tony


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PostPosted: Thu Apr 06, 2017 4:36 am 
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Best of both world's would the NP electrolytic with a film by-pass adding up to your 35 ufd value.

Gary


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PostPosted: Thu Apr 06, 2017 12:04 pm 
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Hi Gary,
No, it doesn't work like that. The dielectric in electrolytic capacitors absorbs some of the signal energy which is measured as a loss. This is fine when the speaker is voiced for it. Film capacitors are more perfect capacitors and have far less loss than many other types. The down side is that they don't carry as much current, which manifests itself as falling capacitance over time (the film is burning off). If you put small capacitors, or even the same capacitance, the losses in the electrolytic capacitor still exist and will colour the sound. There is no point in bypassing electrolytic capacitors with film capacitors in crossovers and audio pass applications.

With power supplies it is a different story because you are dealing mostly with DC. High frequency capacitors will help lower the output impedance (above your range of hearing) to make everything more stable. But this is an entirely different situation and people keep mixing them up. If you hear a positive difference when bypassing these capacitors, you have just experienced "expectation bias". Differences are all above your range of hearing, and not by just a little bit.

-Chris


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