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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Sat 01, 2020 7:33 am 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3470
Location: Lexington, KY USA
It would be interesting to see if the transistor is PNP or NPN. My guess is that it is the more common PNP, and that the collector and emitter are reversed. This can be done with some early germanium parts because of the high base emitter breakdown voltage. This usually delivers somewhat lower gain.

I'm assuming, of course, that the wiring diagram is actually correct.

I wonder if the "designer" had any idea, or just tried different things until he got a station he could hear. The circuit does not entirely make sense. But that doesn't mean it can't work at all.

Remember, this was an era when transistorized audio amplifiers utilizing "grid leak" bias shipped commercially. The lower priced germanium transistors were often so leaky they would bias themselves.

Ted


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Sat 01, 2020 7:44 am 
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Joined: Mar Sun 14, 2010 2:51 am
Posts: 494
Location: Newport, Oregon, 97365 U.S.A.
I think the 'red dot' means a CK722, doesn't it? I don't know of any other transistors that had that mark, except maybe some early Japanese transistors i seem to recall. I think you're right about him just trying things. None of his sets really break ground as new circuits.
The diode - input circuit i was thinking of, was the "Interflex". Gernsback's lit says it delivers more audio output than the common gridleak detector. But i found the ad i was thinking of. It offered a collection of parts for $5, parts to build a tube + transistor set, but no "circuit board". It talks about a "special detector".


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Sun 02, 2020 8:12 pm 
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Joined: Sep Sat 29, 2012 6:32 pm
Posts: 938
Location: 13760
I wasn't expecting such a strong response!
John: No, I haven't gotten it working yet, but I do plan to try next time I do some soldering.
Hue: Your second transistor layout makes a lot more sense to me. Also, since the schematic that came with my set said "CK722" specifically, and has "dot" marked on it, I'm guessing that's the transistor used in your schematic too.

My set also contains a mysterious "yellow unit" and "blue unit", which may be more than just simple capacitors or resistors.

I may also try to build the amplifier described in my schematic, but working CK722s are quite expensive, and I have plenty of other vintage germanium transistors, so I will probably use substitutes instead.


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Mon 03, 2020 12:40 am 
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Joined: Mar Sun 14, 2010 2:51 am
Posts: 494
Location: Newport, Oregon, 97365 U.S.A.
Since "RED" has to be a resistor and capacitor in parallel, we can maybe guess that "BLACK" also has the same components. I thought too maybe the transistor is a 2N170 NPN, or maybe he even painted the dot on a transistor ? Does not make sense any way you analyze the circuit.


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Mon 03, 2020 12:44 am 
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Joined: Sep Sat 29, 2012 6:32 pm
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Location: 13760
Other manufactures sold "fall out" transistors as well, which were often completely unmarked (since they were one step above scrap). So it's quite possible Mr. Eker (or his employees) painted dots on the transistors they sold.


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Mon 03, 2020 2:19 am 
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Joined: Mar Sun 14, 2010 2:51 am
Posts: 494
Location: Newport, Oregon, 97365 U.S.A.
But even the "floor - sweepings " transistors followed the C - B - E row pattern, right ? So it looks like the earphone has to be either to the collector or emiiter.
If the earphone goes to emitter, emitter follower circuit, then the collector has to go right to B+, and the other side of earphone has to go to B- ground.
I am stumped, got to admit.

I noticed that one Ekeradio add offers parts only for a tube - transistor shortwave. It sez it includes min-tube, transistor, 2 capacitors and 4 resistors.
I reckon grid capacitor; plate coupling capacitor; gridleak resistor; plate load resistor, and two resistors for the transistor bias. That looks like a more
conventional, rational circuit.

BTW, some of the "soap dish" model one - tube radio ( the yellowish box shown on page 1 ) sold last year in California, had 39 cent price stickers on them.


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Tue 04, 2020 8:34 am 
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Joined: Jan Tue 16, 2007 7:02 am
Posts: 3470
Location: Lexington, KY USA
At least one of the above photos showed what looks like a TO-5 transistor among the parts. Not a CK722.

It is possible that the transistor type varied depending on supply.

The wiring diagram for the hybrid set only makes sense for a PNP emitter follower. If the transistor is doing anything. I suppose he could have just used duds.

Ted


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Tue 04, 2020 9:09 am 
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Joined: Mar Sun 14, 2010 2:51 am
Posts: 494
Location: Newport, Oregon, 97365 U.S.A.
I cannot see any way to wire this as an emitter follower. The collector will never be at signal ground.


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Tue 04, 2020 9:25 am 
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Joined: Mar Sun 14, 2010 2:51 am
Posts: 494
Location: Newport, Oregon, 97365 U.S.A.
Well, what about this:
Use NPN transistor. We can "probably" assume with some probability, the earphone goes to the collector; and that the resistor must either be in the base or emitter leg.
So leave the collector to earphone. Run the base to the tube plate. Run the emitter to the tube +1.5 filament.
The base resistor limits the base current, sets the resting current. The tube plate current, i am taking a semi-educated guess from a hybrid circuit i saw in a 1954 Radio News article ( but in that case, a cathode follower to transistor circuit ) will be a fraction of a milliamp, somewhere i'm guessing 0.2 - 0.5, no more.
The collector voltage is now B+ less the 1.5 volt fil battery, which bucks it. 30 - 1.5 = 28.5 which is still pllenty, and these early transistor circuits also used higher voltages than we do now. So maybe we can guess tube drop 15 volts approx, transistor drops 15 volts approx. The transistor current gain for these early
transistors is only in the range 10 - 20, so we don't have to limit the base current very much to prevent transistor saturation. So we have a common emitter
amplifier. Only you have to use NPN and swap the base and emitter in my drawing guesstimate above. Note, i think there may have been some transistors of the time with not the C-B-E lineup in a row ? So maybe my assumption above for C-B-E connection could be wrong. I bought some floor sweeping bags of transistors
back around 1961 and they didn't have the CK722 pinout lineup. ( Maybe that's why my Popular Science schematic 1-transistor regen never worked !! )
What think, do i have a theory, or am i all wet? ( It rains a lot here on coastal Oregon. )


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 Post subject: Re: Unopenend "Ekeradio" radio kit ... to open or not to ope
PostPosted: Feb Tue 04, 2020 9:33 am 
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Joined: Mar Sun 14, 2010 2:51 am
Posts: 494
Location: Newport, Oregon, 97365 U.S.A.
And it looks better if the emitter is connected to the "left" side + of the 1.5 batt, so the 1.5 is not reverse biasing the NPN. But maybe it works well enough as-is,
due to "leaky self bias".


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