A dead Arvin 444-A

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A dead Arvin 444-A

Post by Wildcat445 on Thu Aug 13, 2015 3:14 pm

This little radio is one of those cute little metal radios that I wanted for eons, but did not want to pay what one cost.  I got this one at an auction in a box of junk.  It turns out, it was in that box of junk for a reason.  Placed there with items of equal value, if you get my drift.  In its defense, it has both correct knobs, the foil "dial" is nice and it still has its typically-missing back. And it's cute as a bug's ear in a scratched, rusty, rustic sort of way. 

Now for the bad. If I could have a problem of whatever description, I ran into it with this radio.  Alignment was uber-critical here in fringe country.  I must have aligned this thing a dozen times.  I recapped it, and replaced a couple resistors. I fixed some hack wiring.  The outside looks terrible, but that is cosmetic.  I finally got it working well enough to brag about it to my buddy, Frank.  Frank came over the other day and I was going to show him how good I was that I finally figured out this simple little radio.  I told him that I was going to change the speaker, but I would fire it up to let him hear how well it worked.  So I plugged it in to my isolation transformer, connected it to my longwire antenna, and got nothing.  Just a dead silent radio.  I have no idea what happened.  

This is what I know.  B+ is okay everywhere.  The oscillator is running, proven by negative voltage on the grid of the 12SA7 converter tube and it squeals in another radio.  The negative grid voltages changes somewhat as I move the tuning caps from one end of the dial to the other.  I can get a signal from my signal generator at IF thru from the grid of the converter to the speaker.  I get no signal from the antenna to the grid of the converter tube.  The only components involved would be the antenna coil, a mica cap, the tuning cap and its trimmers.  The antenna coil checks good.  I have another radio with a bad mica in the antenna circuit, so I suspect this one.  The tuner checks okay and has no shorted, or partially shorted, plates.  Nothing has fried or looks burnt.  I guess I'll see if I can scrounge a mica and replace that one and see what happens.  I believe I'll quit buying simple radios.  I'm not skilled enough to get one working.  I'll put them on THE list with two cycle engines, church organs, guitar amps and record changers.

WC

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Re: A dead Arvin 444-A

Post by 75X11 on Thu Aug 13, 2015 3:41 pm

A little mica was what croaked my first console restoration. I have a little Ungar princess heat pistol and picked it out with it. when it would get a little warm, it would start to function then fade back out. Freeze mist can also find them out. That is, if you have them and no cap tester.
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Re: A dead Arvin 444-A

Post by Wildcat445 on Thu Aug 13, 2015 3:58 pm

I have a heat gun. Nothing else really to check a mica cap. I haven't had much problem with micas until just here lately. I reckon I need to get geared up to better check micas. I see there may be a need. Wink

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Re: A dead Arvin 444-A

Post by 75X11 on Thu Aug 13, 2015 4:12 pm

As cheap as they are becoming, I'll have to get around to getting a meter.
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Re: A dead Arvin 444-A

Post by Bill Cahill on Thu Aug 13, 2015 4:58 pm

No micas can be trusted anymore. They are all breaking down.

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Re: A dead Arvin 444-A

Post by 75X11 on Thu Aug 13, 2015 5:31 pm

Doveryai no proveryai.

(Trust but verify) :-)
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Re: A dead Arvin 444-A

Post by Spivey on Mon Dec 26, 2016 8:15 pm

Wildcat, What color is your 444? I know the thread is somewhat old but did you ever get your Arvin going?

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