Help With BC-314 power up

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creinemann
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Help With BC-314 power up

Post by creinemann » Sun Dec 17, 2017 1:46 pm

Looking for someone to give me some tips on powering on a BC-314. I have replaced the Dynamotor with one I rebuilt. It's going from 12v to about 225v DC. When I turn on power to radio at the MVC /AVC switch the dynamo will spin up and I get power (225V) but, nothing comes on at all in the radio itself. The dial lights are not even coming on. Fuses are good, tested them, bulbs are good. Shouldn't I at least get them to light up? Any suggestions or leads on who I might talk too?
Carl Reinemann
Wisconsin
Military Radio Pages at

https://usradioguy.com/wwii-radio/


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lynchgj
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Re: Help With BC-314 power up

Post by lynchgj » Sun Dec 17, 2017 8:01 pm

If memory serves, the band lamps do not illuminate on the 314. I guess this was to conserve battery power.

My first thought is to recheck the wiring. When these radios are DC powered, it is through the front panel connector, and tube filament power comes from there, and not the 12 volts to the DM-21.

If you don't already have a manual, they are easy to find along with schematics online. Turn the unit on and verify you have 6 volts on the tube filaments. The tubes filaments are 6 volts, so they are parrelled, so a filament failure in one will take another tube out as well.

Verify you have your 225VDC on the plates circuits of the tubes. Make sure you are using high impedance headphones and/or speaker. The LS-3 speaker is 8,000 ohms and a 16 ohm speaker basically shorts it out. Start from the audio output end, vary the volume and see if you hear noise in the speaker. if you do, then you can work back through the receiver for other possible failures. There is some troubleshooting guidance in the manual. And of course, the tubes have to be in good working order.

Good luck

Gary
1- SCR-399 (w/1945 HO-17(MRC-2) + RC-58 FAX & SCR-510
1- PE-95K - P/O K-52
1- G518 - P/O K-52
2- SCR-536
1- SCR-528
1- SCR-506
1- SCR-300
2- SCR-282
2- BC-611
1- TG-7-B Functional

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wa5cab
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Re: Help With BC-314 power up

Post by wa5cab » Tue Dec 19, 2017 10:06 pm

The tube heater wiring is series-parallel. So if one of a series pair goes open, the other one loses heater power.

First thing to check are the jumpers on the terminal strip that all of the wires coming out of the dynamotor are soldered to. I'm not certain whether your receiver had a dynamotor in it that you replaced or that it had nothing in it. If it had nothing, check that all of the jumpers are in place for dynamotor operation. If it had no dynamotor, some PO may have been converting it to use an RA-20 and didn't finish the job. Some of the jumpers have to be moved if the set is to be operated off of an RA-20 (which technically would make it a BC-344).

If you don't have the TM 11-4002 Repair Manual, I sell a reprint. There are no common failure points in a BC-314. If it doesn't work, the problem could be anywhere. First thing that I would do is to test the tubes, removing one at a time. As you pull each tube, check that the tube is the correct one for that socket. Second thing that I would do, given that the dial lamps don't work (they have worked in all of the ones that I've seen) is to check the 12-14 VDC distribution to and through the tubes. If that's all OK, start at the output with an appropriate signal generator and work back toward the antenna until you lose the signal. Fix that problem and continue.
Gunner
USN Retired
MVPA 9480

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creinemann
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Re: Help With BC-314 power up

Post by creinemann » Sat Dec 23, 2017 10:39 am

Thanks,
Giving your suggestions a shot

Carl
Carl Reinemann
Wisconsin
Military Radio Pages at

https://usradioguy.com/wwii-radio/

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lynchgj
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Re: Help With BC-314 power up

Post by lynchgj » Tue Dec 26, 2017 8:14 pm

Good points all. Do keep us posted with your progress. Also, could you give us a synapses of your electronic skills and test equipment. These radios may seem simple, but simple means very cleverly designed and a possibly nightmarish troubleshooting ordeal as even a wire is a component. So it's a great challenge to make things run again. For instance, just a 1/4 inch difference in the length of a grid wire in an IF stage, can mean no signal. In the old world, signal wire lengths were as much a component as a tube. So keeping things original in the RF area is very meaningful.

But remember, kids were repairing them in WWII and as recently as Viet Nam. We can do this.

Gary
1- SCR-399 (w/1945 HO-17(MRC-2) + RC-58 FAX & SCR-510
1- PE-95K - P/O K-52
1- G518 - P/O K-52
2- SCR-536
1- SCR-528
1- SCR-506
1- SCR-300
2- SCR-282
2- BC-611
1- TG-7-B Functional


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