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 Post subject: Americana FM-10 capacitor Questions and other issues
PostPosted: Feb Wed 11, 2015 4:41 am 
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Joined: Sep Mon 10, 2012 10:41 pm
Posts: 4025
Location: Phoenix, AZ
I have been working on this radio since I got it off ebay the other day.

1 cap is a .02uf 250v (fm switch to ground), 1 is a .2uf 250v (tone control), and one is .1uf 150v (across output of 2 transistors to output transformer), all oil filled.

Why such high voltage ratings in a radio where the max voltage is 6v DC?

Why use oil filled instead of Ceramics or some other type? This radio is full of ceramics.

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 Post subject: Re: Americana FM-10 capacitor Questions
PostPosted: Feb Wed 11, 2015 4:48 am 
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Location: Vincennes Indiana
My guess is they already paid for them so why not use them.


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 Post subject: Re: Americana FM-10 capacitor Questions
PostPosted: Feb Wed 11, 2015 6:22 pm 
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Location: Phoenix, AZ
Sams shows those caps in those values so I doubt it's a case of using up extra stock.

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 Post subject: Americana FM-10 AM fades out
PostPosted: Feb Thu 12, 2015 4:02 am 
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Location: Phoenix, AZ
This radio works great on FM, but when switched to AM the volume has to be turned all the way up and it will still only pickup strong stations. The audio will start fading almost immediately and after a while you can only pick up something by touching the ferrite antenna. Then that to will fade. Switching to FM and back again causes the audio to come back for a very short time before quickly fading.

This is a link to the schematic:
https://www.dropbox.com/s/dxkewb2b7xtwtn4/am.jpg?dl=0

The schematic defaults to all switches set to FM so I modified the Schematic to have all switches in AM. I am not having much luck tracing the circuit, as part of the FM circuit is used by the AM circuit.

I have replaced all the electrolytics as some were bad and others were on the way out. There are still 3 oil filled caps that I need to replace, but I am waiting on an order for that. The radio did not work at all when I got it. As I replaced each component I checked the radio operation and FM showed improvement but AM did not change in any way I could notice. AM never worked right from the start.

Any ideas on what would cause AM to not work properly?

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 Post subject: Re: Americana FM-10 AM fades out
PostPosted: Feb Thu 12, 2015 5:48 am 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 18926
Location: Albuquerque, NM 87123
Seems like an AM oscillator problem. I would replace any electrolytics in that circuit and possibly do a thermal test of the transistor.


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 Post subject: Re: Americana FM-10 capacitor Questions and other issues
PostPosted: Feb Thu 12, 2015 1:27 pm 
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Joined: Jan Thu 01, 1970 1:00 am
Posts: 20963
Location: Utica, NY 13502 (USA)
I would wait until you have replaced those Japanese "oil filled" caps. These are notorious for going leaky. I can't see where they are used in the schematic but the symptom sound like an AGC problem. Also, the germanium transistors used in this set have a history of developing leakage which could affect operating constants.

Dave


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 Post subject: Re: Americana FM-10 capacitor Questions and other issues
PostPosted: Feb Fri 13, 2015 4:50 am 
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Joined: Sep Mon 10, 2012 10:41 pm
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Location: Phoenix, AZ
The recap of all the oil filled caps and all the electrolytics fixed the fading volume on AM, however I only get 620am (the antenna is 1 mile away from me), and a few stations way up on the high end of the dial.

Also doing a just by ear alignment, I cannot move the high end down the dial, so I get 1580 where 1620 should be and cannot make it go to where it should be.

It also does something weird where it gets to a certain point move lower on the dial where it goes pop and I get nothing till 620. So I get 1580 then a couple of barely audible stations then pop around 1100 then nothing but static till 620 then static down the rest of the dial.

I am wondering if the tuning cap is damaged internally on the am section. I won't be able to tell until I can do a real alignment.

FM could use an alignment as I get stations in 2 places, one fainter than the other.

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 Post subject: Re: Americana FM-10 capacitor Questions and other issues
PostPosted: Feb Mon 03, 2020 8:44 pm 
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Joined: Jan Thu 14, 2016 9:29 pm
Posts: 165
I know this topic is extinct and this is a long shot, but does anyone still have the service info they would be prepared to share, please?


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