Forums :: Resources :: Features :: Photo Gallery :: Vintage Radio Shows :: Archives :: Books
Support This Site: Contributors :: Advertise


It is currently Dec Sat 15, 2018 4:47 pm


All times are UTC [ DST ]





Post New Topic Post Reply  [ 10 posts ] 
Author Message
 Post subject: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Mon 05, 2018 12:05 am 
Member

Joined: Mar Fri 11, 2016 9:20 pm
Posts: 40
This is a bit of a different question regarding my current project so i started a new thread. The schematics that I have for this Atwater Kent Model 74 do not specify polarity for the filter caps. They are quite low in value (1-2 mF) and I know there are non-polarized e-caps and film caps available in those values. Would either be suitable replacements or should I stick with regular polarized electrolytics and use my best judgement on their polarity? If either substitution would work, is there anything I need to be concerned about? Additional precautions, etc?


Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Mon 05, 2018 12:26 am 
Member
User avatar

Joined: Jul Mon 11, 2011 9:04 pm
Posts: 1682
Location: Lexington KY
On a set that early I would recommend using non polar caps. This chassis never had wet electrolytic's from the factory. You could use polarized caps, make sure the polarity is correct.

Good luck

If you go with polarized caps. Two go to a chassis ground (negative end of cap), Two others have the neg lead going to HV center tap on your power transformer secondary.


Jon

_________________
Capehart

"The finest in music plus radio entertainment"


Last edited by ketron281989 on Mar Mon 05, 2018 12:39 am, edited 1 time in total.

Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Mon 05, 2018 12:30 am 
Member
User avatar

Joined: Jan Thu 01, 1970 1:00 am
Posts: 23383
Location: Haledon, NJ, usa
The considerations would be
1.)availability in required capacitance and voltage range
2.) physical size/space room.
3.) cost

_________________
To be a man, Be a non-conformist, Nothing's sacred as the integrity of your own mind.
-Emerson


Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Mon 05, 2018 1:21 am 
Member

Joined: Mar Fri 11, 2016 9:20 pm
Posts: 40
Replacements would be just a few bucks more for non-polar caps so it's worth it to me to just use what the manufacturer recommended. If they were $50 each like those oil filled caps some people use for guitar amp stuff then yeeeahhh.. I'd
be looking at alternatives. As for non polarized caps, which would you recommend? Justradios has both non-polarized electrolytics and film caps in appropriate values, and if necessary I can always hollow out the old filter cap can on the top of the chassis to make room. It's about 4 inches cubed.


Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Mon 05, 2018 1:37 am 
Member
User avatar

Joined: Dec Wed 25, 2013 7:57 am
Posts: 2970
Location: USA
I think we're talking about this Atwater Kent 74:

viewtopic.php?f=6&t=336822&p=2821876#p2821876

The radio should work the same with either type; make sure voltage rating is sufficient.

_________________
"What goes around comes around." (Karma)


Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Mon 05, 2018 3:29 am 
Member
User avatar

Joined: Jul Mon 11, 2011 9:04 pm
Posts: 1682
Location: Lexington KY
JasonWatkins wrote:
Replacements would be just a few bucks more for non-polar caps so it's worth it to me to just use what the manufacturer recommended. If they were $50 each like those oil filled caps some people use for guitar amp stuff then yeeeahhh.. I'd
be looking at alternatives. As for non polarized caps, which would you recommend? Justradios has both non-polarized electrolytics and film caps in appropriate values, and if necessary I can always hollow out the old filter cap can on the top of the chassis to make room. It's about 4 inches cubed.



Go with antique electronic supply U.S. based, you will get your parts within a few days as a result. Just radio's is great for those odd hard to find values, they take a few weeks to receive though. AES will have your values and sent out quickly!

Jon

_________________
Capehart

"The finest in music plus radio entertainment"


Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Tue 06, 2018 12:36 am 
Member

Joined: Jan Tue 16, 2007 7:02 am
Posts: 2660
Location: Lexington, KY USA
Electrolytic caps of any sort are a poor choice for replacing paper filter caps.

Non-polar electrolytics are an even poorer choice than regular polarized electrolytics.

Unless there is some good reason not to do so, you want to use film dielectric replacements. Probably the best bet is polypropylene caps.

The film caps are reasonably priced, and easily found in the correct values and voltage ratings.

Electrolytic caps can work, but some care must be taken to select parts that will give reasonable life in this application.

Generally any electrolytic cap will give shorter life than a suitable film cap.

Ted


Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Tue 06, 2018 2:32 am 
Member

Joined: Mar Fri 11, 2016 9:20 pm
Posts: 40
Yes this is the same AK Model 74. I figured I was changing the topic a bit so a new post would br in order. I'm about to do it again though... Those film caps are dirt cheap so I'm going to go with those. I'm just not used to seeing anything like that. Electrolytics have been in every radio I have worked on until now.

There are a few resistors in this unit that I am not familiar with. They appear to have a ceramic body with metal caps on each end. Are these just plain old carbon resistors churched up or is there more going on? Higher wattage maybe? I was thinking about going with higher wattage resisters over the whole radio so they fit in those neat little lugs better anyway, if that's even what they are.


Attachments:
rsz_1rsz_img_20180305_201355404.jpg
rsz_1rsz_img_20180305_201355404.jpg [ 101.02 KiB | Viewed 407 times ]
Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Tue 06, 2018 3:00 am 
Member

Joined: Mar Fri 11, 2016 9:20 pm
Posts: 40
Thank you for recommending them. I've been looking them over and their selection looks good. I didn't even know they were around. :)

ketron281989 wrote:
JasonWatkins wrote:
Replacements would be just a few bucks more for non-polar caps so it's worth it to me to just use what the manufacturer recommended. If they were $50 each like those oil filled caps some people use for guitar amp stuff then yeeeahhh.. I'd
be looking at alternatives. As for non polarized caps, which would you recommend? Justradios has both non-polarized electrolytics and film caps in appropriate values, and if necessary I can always hollow out the old filter cap can on the top of the chassis to make room. It's about 4 inches cubed.



Go with antique electronic supply U.S. based, you will get your parts within a few days as a result. Just radio's is great for those odd hard to find values, they take a few weeks to receive though. AES will have your values and sent out quickly!

Jon


Top
 Profile  
 
 Post subject: Re: Non-Polarized electrolytic or film caps for filtering
PostPosted: Mar Tue 06, 2018 1:53 pm 
Member
User avatar

Joined: Jul Tue 15, 2008 6:13 pm
Posts: 5479
Location: Gretna, Nebraska
Yes, those are just carbon resistors in a ceramic tube. Often they will have drifted much higher in value. You can replace them with a 1 watt-rated modern replacement.


JasonWatkins wrote:
Yes this is the same AK Model 74. I figured I was changing the topic a bit so a new post would br in order. I'm about to do it again though... Those film caps are dirt cheap so I'm going to go with those. I'm just not used to seeing anything like that. Electrolytics have been in every radio I have worked on until now.

There are a few resistors in this unit that I am not familiar with. They appear to have a ceramic body with metal caps on each end. Are these just plain old carbon resistors churched up or is there more going on? Higher wattage maybe? I was thinking about going with higher wattage resisters over the whole radio so they fit in those neat little lugs better anyway, if that's even what they are.

_________________
http://www.vintagerestorationservices.com
Paul
...... how hard can it be?


Top
 Profile  
 
Post New Topic Post Reply  [ 10 posts ]  Moderators: Marcc, Norm Leal

All times are UTC [ DST ]


Who is online

Users browsing this forum: GlensterTX, Recordman1949, voroush, zbiker II and 8 guests



Search for:
Jump to:  
























Privacy Policy :: Powered by phpBB