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


It is currently Dec Wed 11, 2019 7:23 am


All times are UTC [ DST ]





Post New Topic Post Reply  [ 6 posts ] 
Author Message
 Post subject: Replacement oscillator coil
PostPosted: Nov Sun 17, 2019 8:34 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 999
Location: Germantown, IL USA 62245
Hello,
Crosley 645, 32 volt radio with open oscillator coil. I have 2 Miller coils, a 45c and a 70-osc. I'm hoping one of them will work in this radio. It probably won't have the shortwave band but that's not a problem. I'm not sure if these coils will work or how to connect them. Here's some schematics:

Tom Ackerman


Attachments:
oscillator 1-2.jpg
oscillator 1-2.jpg [ 89.4 KiB | Viewed 224 times ]
MILLER COIL 1.jpg
MILLER COIL 1.jpg [ 82.66 KiB | Viewed 224 times ]
MILLER COIL 2.jpg
MILLER COIL 2.jpg [ 126.98 KiB | Viewed 224 times ]
Top
 Profile  
 
 Post subject: Re: Replacement oscillator coil
PostPosted: Nov Sun 17, 2019 8:53 pm 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 2017
Location: Austin, Texas
The 70-osc has a good chance of working. Do you know how to hook it up from the diagrams? If not, we can put some pin numbers on the schematic for you. Actually, the two schematics are the same except for the SW switch on the Crosley. Just put the first 70-osc coil drawing directly over the coil in the Crosley schematic and the pin numbers will be correct.

The IF frequency of the radio is 450KHz but the 70-osc should have enough range to cover that difference. The main problem will be the capacitance of the tuning cap in the Crosley. It may be OK but you will need to install the coil to see if it can bring the oscillator to the correct frequency.

What equipment do you have to do an alignment?

Jay


Top
 Profile  
 
 Post subject: Re: Replacement oscillator coil
PostPosted: Nov Sun 17, 2019 9:44 pm 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 999
Location: Germantown, IL USA 62245
I have the usual stuff, signal generator, frequency counter, meters, etc. I was concerned about the 32 volts being so much less than the 6A7 usually operated at. The oscillator section of the tuning cap is smaller than the 2 RF sections if that helps anything.

Tom


Top
 Profile  
 
 Post subject: Re: Replacement oscillator coil
PostPosted: Nov Sun 17, 2019 10:55 pm 
Member

Joined: Nov Tue 14, 2017 5:09 am
Posts: 2017
Location: Austin, Texas
frankradio1 wrote:
I have the usual stuff, signal generator, frequency counter, meters, etc. I was concerned about the 32 volts being so much less than the 6A7 usually operated at. The oscillator section of the tuning cap is smaller than the 2 RF sections if that helps anything.

Tom

Tom,

I don't think the low operating voltage is going to a problem but you will just have to try the coil to see if it works.

The smaller tuning cap for the oscillator is probably a good sign since that is more like the later radios that the coil was intended for.

How confident are you that the radio is working other than the oscillator? Will it play if you use your signal generator to inject an oscillator signal? If you can get it to play with the signal generator, set the dial to one of the stronger stations in your area and leave it there.

Assuming the radio is operational, my suggestion would be to install the oscillator coil and verify the oscillator is operating. You can usually do that by checking for a negative voltage on pin 5 of the 6A7.

To adjust the oscillator coil, back the slug all the way out and turn on the radio with the dial set to a strong station. Move the tuning slug inward until you receive the station. You can check for the strongest signal by tuning for the highest negative voltage on capacitor 11B.

If the other stations don't come in at the correct dial settings, you may need to go back to the oscillator coil adjustment and look for a second signal peak with the slug further into the coil.

Jay


Top
 Profile  
 
 Post subject: Re: Replacement oscillator coil
PostPosted: Nov Mon 18, 2019 1:06 am 
Member

Joined: Jan Thu 01, 1970 1:00 am
Posts: 999
Location: Germantown, IL USA 62245
Thanks for the help. The radio has been recapped and was working a few months ago. I can get an IF signal through it, so getting the oscillator working should do it.

Tom


Top
 Profile  
 
 Post subject: Re: Replacement oscillator coil
PostPosted: Nov Mon 18, 2019 1:13 am 
Member

Joined: Jan Tue 16, 2007 7:02 am
Posts: 3256
Location: Lexington, KY USA
If your counter is reasonably sensitive, you can read the oscillator frequency directly, and not be wearing out the adjustment for the coil.

Note that you want to set the slug in the coil near the low end of the band, and use the trimmer near the high end. That should let you get the alignment dead-on at those two points, and with some luck, be pretty close across the band.

Don't toss the old coil. At some later date, you or someone else may want to see if it can be repaired.

Ted


Top
 Profile  
 
Post New Topic Post Reply  [ 6 posts ]  Moderators: Marcc, Norm Leal

All times are UTC [ DST ]


Who is online

Users browsing this forum: Google [Bot], Johnnysan, lorenz200w and 18 guests



Search for:
Jump to:  




























Privacy Policy :: Powered by phpBB