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 Post subject: atwater kent parts
PostPosted: Aug Fri 13, 2021 4:33 pm 
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Joined: Aug Fri 13, 2021 4:20 pm
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I am new to this forum so excuse me if I am doing this wrong, I am having a hard time finding parts. I have a model 82 Atwater Kent. Just purchased for a great price, cosmetically original, but none working. I turn on and after a few minutes notice smoke. After further investigation, I believe the transformer is bad, has the telltale tar and goo around the transformer. Where do I get parts for this unit.
Thanks, Len


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 Post subject: Re: atwater kent parts
PostPosted: Aug Sat 14, 2021 12:21 am 
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Len wrote:
I am new to this forum so excuse me if I am doing this wrong, I am having a hard time finding parts. I have a model 82 Atwater Kent. Just purchased for a great price, cosmetically original, but none working. I turn on and after a few minutes notice smoke. After further investigation, I believe the transformer is bad, has the telltale tar and goo around the transformer. Where do I get parts for this unit. - Thanks, Len
First, welcome to the forums.

Yes, you probably have a cooked power transformer. Unfortunately this was probably caused by shorted power supply electrolytic capacitors. The capacitors are relatively easy and inexpensive to replace. The power transformer, not so much.

The documentation for your radio is here: http://www.nostalgiaair.org/Resources/480/M0001480.htm

Unfortunately the documentation does not present the power transformer secondary AC voltage. So we are left with having to make an educated guess. Since the DC voltage to the audio output tube is about 240 VDC, we're going to estimate the AC voltage from the power transformer is 480 VCT (Volts Center Tapped, or 240-0-240 ACV).

Now we have to go here and add up tube current... https://frank.pocnet.net/
Attachment:
Transformer.png
Transformer.png [ 10.31 KiB | Viewed 1073 times ]
This gets us to something like...

Transformer I20 VAC Primary, 240-0-240 VAC secondary
5.0 VAC at 2.0 Amps
2.5 VAC AT 11 .0 Amps
240-0-240 VAC at 75 mA

Then it has to fit the physical size available in that radio (I have no way of knowing that).

The tough part is the 2.5 VAC filament (not too common these days). Hammond makes a pretty good selection of replacement transformers, but none listed with the 2.5 VAC filament winding. If they had one it would run you about $80, but they don't so that's kind of a moot point.

You might want to post a request for a power transformer in the Classified section here ( viewforum.php?f=15 ) and include the above guesstimated specifications for an Atwater Kent Model 82 and provide the mounting dimensions. Then cross your fingers.

Sorry, that's about the best I can do other than you might ask if anyone has a basket case model 82 with a good transformer. Oh, and don't install any replacement transformer without changing the capacitors that probably caused this problem in the first place.

That's why we try to head people off before they apply power, but it's not necessarily your application of power that did the damage. I suspect it may have already been damaged by whoever sold it (why it sold for such a good price).

Best of luck,

Curtis Eickerman

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 Post subject: Re: atwater kent parts
PostPosted: Aug Sat 14, 2021 3:45 pm 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Bristol TN 37620
Nice explanation Curtis.


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 Post subject: Re: atwater kent parts
PostPosted: Aug Sat 14, 2021 6:07 pm 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 4719
Location: Lexington, KY USA
Many working transformers have goo coming out. Some even smell bad. There is a chance yours will still work, once the overload is removed.

First remove all the tubes and check the DC resistance of each transformer winding.

If the resistances are reasonable, see if the transformer will accept AC line voltage without heating or arcing and sparking. Use a smaller bulb in your dim bulb tester to avoid excessive excitement. Do this with all the tubes still out so there is no load on the transformer. Watch the line current while power is applied, as well as keeping a lookout for smoke or bad sounds..

Check each secondary voltage. Be careful about the high voltage secondary connected to the rectifier tube plates.

Ted


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 Post subject: Re: atwater kent parts
PostPosted: Sep Tue 07, 2021 3:17 pm 
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Joined: Aug Fri 13, 2021 4:20 pm
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Thank you all very much, I will check these suggestions out, very helpful.


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 Post subject: Re: atwater kent parts
PostPosted: Sep Tue 21, 2021 12:55 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 1239
Location: St. Louis, MO, USA
The high voltage transformer with a 5 volt winding would be the easiest to get. A 6.3 volt transformer with the high amp rating could be unwound to get you to the 2.5 volts You May be able to tuck the filament transformer some where else on the chassis. I’m not familiar with “real estate” on the chassis but may be worth a try.

Dennis


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 Post subject: Re: atwater kent parts
PostPosted: Sep Tue 21, 2021 5:32 am 
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Joined: Jan Thu 01, 1970 1:00 am
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Location: Olympia WA USA
Often a hamfair can supply you with a good used 5.0V CT (2.5V-0-2.5V) filament transformer if you are unable to find a 2.5 V one. Stancor made them, and likely Triad.

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 Post subject: Re: atwater kent parts
PostPosted: Sep Mon 27, 2021 5:08 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 6046
Location: 253 Blanche St. Plymouth, MI USA
the AK model 80, 82, 84, and 86 series are known for bad power transformers. To test it, remove the type 80 tube and power up the radio. all the other tube filaments should light.... listen for any quiet popping or sizzling sounds from the xfmr. Run it for up to 15 mins, if it stays room temp and no sounds, its likely good .... at least for now .
You can find replacements but they are not easy to find due to the 2.5v filament line you need.

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Mark Oppat
Antique Audio
Plymouth, MI
http://www.oldradioparts.net


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