AW12 Jensen speaker field coils question

[Corby Dawson]

Hi,

 

I have two sets of wires coming out of the housing one reads open and the other reads 760 Ohms.

What shouldI be reading?

 

Thanks,

 

Corby

[David C. Poland]

Corby -   You are correct that there are 2 field coils.

My records show.....  One field should be about 900 ohms - the bias for the output 45 tubes (the two large pins on the 6 pin speaker plug).   The other field coil should be about 2500 ohms - and is for the B+ high voltage circuit and also connects to the center tap of the output transformer.   Do trace your wiring to identify and verify each field coil,   lest the your "good" field is really faulty B+ coil. And I suggest you check that your problem is not merely a bad solder joint.

The Riders diagram for the (Scott 12 tube) Deluxe Allwave Deluxe with AVC  shows the twin speakers (Rola) Scott supplied until very early 1933 (approximately). Then Scott upgraded to the 12 inch Jensen Pedestal speaker for this model. The twin speaker and the pedestal speaker are electrically the same (are interchangeable).  

Good luck with your speaker.   -Dave 

[Corby Dawson]

Dave, Thanks! I did find an AW15 manual that with my AW12 manual was able to answer how the speaker is connected.

The "good 760 Ohm" coil is the one biasing the 45 tubes, The open one must be the 2500 Ohm B+ coil. I'm looking for someone to repair the speaker.

I'm starting to look at the chassis and have a question there also. On the left side variable capacitor the stud for the compression trimmer is gone. It looks like at the base of the assy. there is a compression cap. Did someone add this to take the place of the broken one or is it used for an original purpose? SEE PIX

Also when I recap do the bathtub caps usually need replacement?

 

Thanks,

 

Corby

David C. Poland said:

Corby -   You are correct that there are 2 field coils.

My records show.....  One field should be about 900 ohms - the bias for the output 45 tubes (the two large pins on the 6 pin speaker plug).   The other field coil should be about 2500 ohms - and is for the B+ high voltage circuit and also connects to the center tap of the output transformer.   Do trace your wiring to identify and verify each field coil,   lest the your "good" field is really faulty B+ coil. And I suggest you check that your problem is not merely a bad solder joint.

The Riders diagram for the (Scott 12 tube) Deluxe Allwave Deluxe with AVC  shows the twin speakers (Rola) Scott supplied until very early 1933 (approximately). Then Scott upgraded to the 12 inch Jensen Pedestal speaker for this model. The twin speaker and the pedestal speaker are electrically the same (are interchangeable).  

Good luck with your speaker.   -Dave 

[David C. Poland]

Maybe someone has a receiver on a shelf where it is convenient to check. Mine is in a cabinet and I don't expect to have it out anytime soon. I wouldn't be overly concerned at this point. Meanwhile, replace outdated capacitors and basic continuity of coils and transformers. power it up, check voltages and see how it performs.

You should seek complete service info for the AW-12. Kent may have PDF's of the service data available.

Incidentally, the Jensen pedestal speakers  for the AW-12 and the AW-15 are not interchangable.

[Norman S Braithwaite]

Those "bathtub" capacitors along the back of the chassis house not only a capacitor but also a choke.  Unless the capacitor within these units is basically shorted or sparking, they will still work.  If bad, it is best to remove and open the sealed units, remove and replace the capacitor within the bathtub, and reinstall the units.

Norman

[Corby Dawson]

Norman S Braithwaite said:

Those "bathtub" capacitors along the back of the chassis house not only a capacitor but also a choke.  Unless the capacitor within these units is basically shorted or sparking, they will still work.  If bad, it is best to remove and open the sealed units, remove and replace the capacitor within the bathtub, and reinstall the units.

Norman

[Corby Dawson]

Norman,

 

Thanks for the info! I see three big ones on the rear panel. Are those the only ones with the additional choke inside?

I also have smaller ones 3 on the right panel and 5 on the bottom of the chassis as well as one in the power supply unit.

I'll test them all for leakage with my LC53 Capacitor analyzer. Are the capacitors in the shield cans mica? Do they often need replacement?

 

Best Regards,

 

Corby