Emerson CF255

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Emerson CF255

Post by mtroy1369 on Mon Nov 26, 2012 12:22 am

I am new to this forum and relativly new to radio restorations. (! Year)
I am 75 years young and truly enjoying my new hobby.
I have recapped and replaced all resistors in this "little radio".
It has two tubes a 12B8GT and a 32L7GT, both checked out okay.
I tried powering up on the ISO trans and my variac but had a dead receiver.
Neither the pilot light or tubes lit up.
I checked the power cord (one of those curtain burners with the resistance in the power cord and pilot light section)
and found a wire that was burned through. It was one of the resistance wires inside the cloth cover.
I reconnected the burned wire and the radio played.
The power cord does get quite warm. Is it dangerous to run the unit with this cord??
I would prefer to replace the cord with a new cord but am concerned on how to replace the built in resistance in the old cord.
What size resistor or resistors do I replace the R7 and R8 with?? (R7,R8 taken from schematic)
Where do I connect the replacement resistor/ resistors??
Thank you for any suggestions and imput!
Matt
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Re: Emerson CF255

Post by Bill Cahill on Wed Nov 28, 2012 7:09 pm

Hi. Welcome to Tube Radio Forums. Sorry I missed your post.
Follow the schematic inside the chassis is where they should go. I would reccommend at least 20 watt resistors as the tubes amount to considerably less total volatage than what's on power line.
I would replace the power cord. Glad it's working, but, I'm fairly sure cord is rather crispy with age. Be careful, that "Cloth" on the inside of cord is asbestos.
Glad you got radio playing.
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Re: Emerson CF255

Post by GaryRabbitt on Thu Nov 29, 2012 2:47 am

Hi Matt,
You might want to know that some guys have changed the tubes that use a 70 volt filament and a 25 v filament. Then use a resistor to take up the rest of the voltage.
I guess it's ok to post a link to this thread:
http://www.antiqueradios.com/forums/viewtopic.php?f=6&t=177987

The cords were normal to run warm back in the day, but a cord that okd I'd be wary of. There are no resistance cords made anymore, even new old stock ones are brittle and unsafe.

If you are only getting the set into working condition then you might leave it alone at this point. I wouldn't power something like that to use on an everyday basis. If the set were mine, I"d have it playable as you have there. Power it up occasionally for a show and tell I guess. If you want the set to be played for hours every day, than I'd suggest you do the modification so it can run it usung a normal, safe cord.
Good luck!
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Re: Emerson CF255

Post by mtroy1369 on Thu Nov 29, 2012 11:09 am

Bill & Gary,
Thanks to you both for your response!!
Matt

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Re: Emerson CF255

Post by Ken g on Sun Dec 16, 2012 2:33 pm

out


Last edited by Ken g on Wed Apr 10, 2013 9:35 pm; edited 1 time in total

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Re: Emerson CF255

Post by N7ZAL on Sun Dec 16, 2012 2:48 pm

Welcome Matt and as you can see this is a very helpful forum.
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Re: Emerson CF255

Post by GaryRabbitt on Wed Jan 23, 2013 11:02 pm

Matt, if you're still here, go to this page and download the resistance cord capacitor calculator. Scroll almost to the bottom. Sorry to have to post a link, but the calculator link is there along with more tech stuff that would take an hour to copy.
http://www.vintage-radio.com/repair-restore-information/valve_dropper-calcs.html

There are other methods, and some of the math is beyond me. But entering your info in to the calculator spreadsheet will give you the values you need for the AC capacitor
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Re: Emerson CF255

Post by mtroy1369 on Mon Jan 28, 2013 11:06 am

Gary,
Thanks again!
Matt

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Re: Emerson CF255

Post by Guest on Mon Jan 28, 2013 11:59 am

Great link Gary, thanks for posting! Smile

You may want to add that to the "Useful Links" forum here.

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Re: Emerson CF255

Post by GaryRabbitt on Wed Jan 30, 2013 12:21 am

Hi Matt,
I had a sketch showing how one guy did the mod to the set. He used higher voltage tubes, then had to drop only a few volts. I know I have the drawing saved on disc, but searching the model number didn't bring it up. I'll have to search manually. If and when I find it, I'll post. Come to think of it, I believe it was Mark Oppat of oldradioparts.com that sent my friend the sketch. I'll get back if I can find it.
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Re: Emerson CF255

Post by GaryRabbitt on Thu Feb 07, 2013 9:58 pm

I found the sketch of the modification that a friend sent me, The friend said that Mark Oppat sent it to him.
He did the modification, and said it worked well.
Disclaimer: This is not my design , and I am not responsible for any damage that might occur. The image is for information puposes only. User assumes all risks. Thank you.
Emerson CF-255 mod. Reduce your screen size to see the whole sketch. This is the way it shows in the TRF Gallery.
http://r20.imgfast.net/users/2514/34/20/40/album/emerso10.jpg
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Re: Emerson CF255

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