mystery radio parts - Videokarma.org TV - Video

jbivy · #1 07-11-2012, 05:28 PM

I picked up a jumble of old radio parts on ebay. Theres two items i cant identify. One is an old breadboard style bakelite tube socket made by Federal. Its for a four pin tube, but for one less than an inch wide at the base.

The other thing is an aluminum square, with a circle design on one side with a terminal in the middle. The other side has several holes and a terminal hookup in the center of that. Its made to unscrew in seconds, on the inside its just two cotton? O-gaskets with what looks like iron filings in between then. I recall some early radio receivers that used iron filings, could this be a form of coherer? Its made by "universal" with patent pending on it.

I'll try to get pics up soon.

bob91343 · #2 07-11-2012, 08:41 PM

Yeah, pictures.

jbivy · #3 07-11-2012, 09:07 PM

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I also picked up the socket, its meant for a tube under 1 inch wide at the base and has the bayonet very low. Its far too narrow to take a tube like an 01a. Was it meant for a short pinned tube? Theres also a 14 embossed on the top.

bob91343 · #4 07-11-2012, 11:19 PM

The tube socket is a bayonet type that fits most 4 pin tubes. Many of them had a tiny pin sticking out the side of the base that fitted into the socket slot, then you twist the tube to lock it into place after pushing it down.

The other item may be a carbon microphone element. Or perhaps a condenser microphone element. I would guess before 1920.

Reece · #5 07-12-2012, 08:09 AM

Pretty sure Bob's right. Check out this carbon mike:

http://www.oobject.com/classic-micro...crophone/1468/

The tube socket may be for early short-pin UV prefix bayonet pin tubes. I don't have one to compare, but a UX-199 which is a little later has a 1-1/8" diameter base. I think the WD-11 and similar were a little narrower in the base.

jbivy · #6 07-12-2012, 06:34 PM

Thanks for the info guys. The mic really had me baffled, ive seen them in movies, but I would never have put 2 and 2 together.

Well I guess im off to search the internet, to see if I can find a way of testing this.

earlyfilm · #7 07-12-2012, 08:58 PM

Quote:

Originally Posted by jbivy

. . . . O-gaskets with what looks like iron filings in between then. . . . .

The stuff inside would have been carbon granules, just like in a telephone transmitter.

Jas.

jbivy · #8 07-12-2012, 11:07 PM

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this is a little amp i picked up. I assume its field coil because of the jacks and numerous transformers. It has a type 80 rectifier and a 2a5 power tube. The heavy aluminum chassis is really well put together, could this have been a kit?

Reece · #9 07-13-2012, 08:07 AM

Very odd. That switch looks like telephone switchboard equipment, and the Federal name on it would bear that out. If that's a speaker plug shown on the rear, it appears to have a jumper across two pins: that would be to cut the B+ to the output tube in case the speaker were unplugged with power applied, to avoid running the tube with no load. I think it's a homebrew: the socket hole on the rear shows signs of having been "worried" out with a saw and file rather than punched. And screws are used everywhere, some too long, rather than rivets. The knob is very early thirties. This could be a power amp someone cooked up, with power supply too, to add to a twenties radio to get operating juice and speaker power. The other plug on the rear must be for power out to the radio.

jbivy · #10 07-13-2012, 06:27 PM

Quote:

Originally Posted by Reece

Very odd. That switch looks like telephone switchboard equipment, and the Federal name on it would bear that out. If that's a speaker plug shown on the rear, it appears to have a jumper across two pins: that would be to cut the B+ to the output tube in case the speaker were unplugged with power applied, to avoid running the tube with no load. I think it's a homebrew: the socket hole on the rear shows signs of having been "worried" out with a saw and file rather than punched. And screws are used everywhere, some too long, rather than rivets. The knob is very early thirties. This could be a power amp someone cooked up, with power supply too, to add to a twenties radio to get operating juice and speaker power. The other plug on the rear must be for power out to the radio.

Do you think there is anything I should know before i order the new wire and caps for this? Any idea as to how i register the output, so i can determine the size of the speaker this will need? Ive several field coil speakers laying around. I think this would be potentially great to hook up to my three tube regen and well.. not be forced to use my headphones.

earlyfilm · #11 07-15-2012, 11:25 AM

Quote:

Originally Posted by jbivy

Do you think there is anything I should know before i order the new wire and caps for this? Any idea as to how i register the output, so i can determine the size of the speaker this will need?

My original thought was this is a home built code practice beeper, less speaker, and with the jack on the front panel to plug in the key.

Then Tubeology Reece came up with an audio output booster, and that makes more sense. I suspect that the switch can either direct the sound to one of two speakers, or between speaker and headphones, or possibly switch between inputs. There is obviously some 4 wire input (output?) on the front.

Before you start ordering any parts, I'd suggest that you circuit trace and draw a circuit diagram to confirm exactly what you have.

Regarding the size of the speaker, although using a different filament voltage and wired differently, the single 2A5 is electrically equivalent to the more modern 6F6. I have a 63 year old amplifier with a pair of push-pull 6F6G's running a plate voltage of 360V and feeding a 12 inch two-watt speaker with a 1060 ohm field coil. A single 2A5 can deliver only about a half watt. (Maybe one watt with little 'vintage' distortion.)

James

maxhifi · #12 07-15-2012, 11:58 AM

Quote:

Originally Posted by earlyfilm

My original thought was this is a home built code practice beeper, less speaker, and with the jack on the front panel to plug in the key.

Then Tubeology Reece came up with an audio output booster, and that makes more sense. I suspect that the switch can either direct the sound to one of two speakers, or between speaker and headphones, or possibly switch between inputs. There is obviously some 4 wire input (output?) on the front.

Before you start ordering any parts, I'd suggest that you circuit trace and draw a circuit diagram to confirm exactly what you have.

Regarding the size of the speaker, although using a different filament voltage and wired differently, the single 2A5 is electrically equivalent to the more modern 6F6. I have a 63 year old amplifier with a pair of push-pull 6F6G's running a plate voltage of 360V and feeding a 12 inch two-watt speaker with a 1060 ohm field coil. A single 2A5 can deliver only about a half watt. (Maybe one watt with little 'vintage' distortion.)

James

I agree with everything above - except, the 6F6 (and therefore 2A5) puts out similar power to a 6V6, only it is a true pentode instead of a beam power tube. As such it can put out about 4.5 Watts single ended, or about 12-15 Watts push-pull.

What's this mean practically? All the power you'll ever need for a typical radio.

Ref:
http://www.mif.pg.gda.pl/homepages/f.../021/2/2A5.pdf
http://www.mif.pg.gda.pl/homepages/f.../028/6/6F6.pdf

bob91343 · #13 07-15-2012, 12:57 PM

Best to trace the circuit and reverse engineer it to see just what you have there. Then you can decide on its best use.

Reece · #14 07-16-2012, 05:51 AM

Agree with everybody: sketch it all out and then redraw it "nice" and let us see the schematic. Best way. I've done that with orphan sets, just to see where I was.

jbivy · #15 07-17-2012, 07:25 PM

Quote:

Originally Posted by Reece

Agree with everybody: sketch it all out and then redraw it "nice" and let us see the schematic. Best way. I've done that with orphan sets, just to see where I was.

Sounds good to me, but it will be about a week. Im making some changes to my three tube regen right now.

I'll get on sketching out the design then. Id like to hope this is what i think it is, an amplifier. Since then it would be a perfect period piece to use with my radio.

Sorry guys, sitting with headphones on me bugs me to no end and i feel bad using a solid state amp with this.