Radio's "radio trivia"

[Radio]

I'll ask the questions. When the question is answered I'll ask another. (No Googling)

If you open a TO-5 package, what would you find inside?

[Andy N1ORK]

TO-5? plastic pakaging for a semiconductor of some sort?

[Radio]

Close.

[KC1BUD]

TO5 isn't that the transistor? Three leads and one junction.

It has been too many years for sure.

[TXiceman]

Small 3 pin transistor with Collector, Emitter and Base Leads.

[Radio]

Here's a TO-5 package. Inside you would find a transistor. Or maybe a voltage regulator or op-amp. It is interesting to note TO-5 refers only to the can, and not the number of legs.

[Radio]

Next question: In this vintage 1950's AM radio, you would find 5 tubes.

A. Without looking, how many of them can you name?
B. These five tubes were selected/designed to save cost in radio manufacturing. What was the technical advantage they provided?

[W9WLS]

TO-5 , Two Japanese midgets with 3 jumpers and one grain of rice.

[WD8QBQ]

Guessing, 6al6 and 12au7, for two

JIM

[Andy N1ORK]

The filaments in the tubes were wired in series so you wouldn't need a transformer for the power supply and the plate voltages could all run on 115vdc. Usually 1/2 wave rectification and cap filtering. You just had to be careful that the polarity of the AC plug was correct if you were going to work on it. The radio, however, worked either way. Not sure of the tube compliment, but I think one was a 12at... something.

[Radio]

Originally Posted by Andy N1ORK

The filaments in the tubes were wired in series so you wouldn't need a transformer for the power supply and the plate voltages could all run on 115vdc.

Correct!

Now, how many of the five tubes can we remember.

There were several variants over about 30 years. Any tube from any variant counted OK.

[Andy N1ORK]

Hmmm..., let's see............ 117vac / 5 tubes averages out to about 23.4 filament volts per tube. I don't recall if any of the tubes had 24v filaments, Hmmmm...........
Have to check out the old set I have in a wooden case when I get home.

[Radio]

Originally Posted by Andy N1ORK

Hmmm..., let's see............ 117vac / 5 tubes averages out to about 23.4 filament volts per tube. I don't recall if any of the tubes had 24v filaments, Hmmmm...........
Have to check out the old set I have in a wooden case when I get home.

Hint: The filament voltages all added up to 121 volts. But they were not all equally divided 12 + 12 + 12 + 50 + 34 = 121.

[Andy N1ORK]

OK, enough of a chance..............here goes:
50b5,12ba6,12at6,12be6,35w4
at least in the one I have.
73

[Radio]

I said you couldn't Google. Never said you couldn't look in a radio!!

Here's the answer. Well, here is one of several variants. As you can see there is no heavy expensive power transformer. And it will run on AC or DC if you can find 115v of battery!

Many of these were repaired "while you wait" as the tech simply swapped tubes until it worked. Sometimes you could tell if a tube was "gassy" because it lit up purple. Some were intermittent and a tap with a pencil eraser would indicate that. But if you lost a filament then you could either swap tubes until you found it, or really impress your customer by locating the open filament with a meter, and fixing the little radio on the first try.

[Radio]

You have a shoebox full of these at the hamfest bone yard for $1 each, new in box. Junior Wannabee gives you $2, says he's rebuilding the Class B final amp in his Grandpa's old Blitzensparker DX50.

What do you do?

[Radio]

I guess I stumped them?

[Andy N1ORK]

I guess you did Wade. Based on the number, there are 4 elemnts (5u4) and a 5v filament, so I guessed it was a rectifier and not much use as a class B amp tube. Didn't know the price value of the tube, but I'm guessing it's more than $2. I'm gonna google it just to find out, but I won't post it here.
73
P.S.
I believe the filament is also the cathode for the 2 plates, ergo it is a full wave rectifier.

[aintgotnun]

Originally Posted by Radio

You have a shoebox full of these at the hamfest bone yard for $1 each, new in box. Junior Wannabee gives you $2, says he's rebuilding the Class B final amp in his Grandpa's old Blitzensparker DX50.

What do you do?

Ah but the question is "What do you do?"...

Since you had them for a buck each and he gives you 2 bucks you give him 2 tubes right?


yeah I'm reachin

[Radio]

After taking Juniors $2, you inform him these are rectifier tubes, not RF power amplifier tubes. If Junior has looked at the Blitzensparker DX50 schematic (or even looked inside the thing) he should know if 5U4's are on his lists of tubes to buy.