2019-04-20 DC to DC Converter for Tube B+

from FB group Building Transistor Radios

Jon Edwards
I’ve built a lot of JTs, they are useful for low power, under 100 mW. I got about 50% efficiency. What you have to do is make sure the reverse voltage emitter to base doesn’t exceed 5V, so it doesn’t waste power.

A better way is to use two transistors in a circuit that has only a single winding on the coil, it’s just an RFC.

Draw up a schematic so we can see what you have.
This can put out higher voltage with a higher voltage zener.


2019-04-18 We Take A Risk Every Time We Touch A Wire

from FB group Bell Telephone of… Apr 21

Jim Engle
One time I was connecting up a POTS modem line and I was getting the crossconnect wire into the 66 block ready to punch them down. BRZZAP! I got zapped by the AC! Some idjit plugged a three prong plug into a 2 prong ungrounded extension cord! The modem and other equipment was hot, a shock hazard! So we take a risk every time we touch a wire.


2019-04-13 Olympus Digital Player Has Flutter

from FB group Vintage Electronics Test Equipment For… Apr 13

I see a Leader wow and flutter meter for sale. This reminded me of a problem I’m having with my Olympus digital recorder/player (WS-822, IIRC). I’m listening to it playing and it’s sounding like there is flutter in the music! That seems crazy to me, I don’t see how a digital player could have flutter. But I swear, it sure seems like it. I’m wondering who or where I can find more info about it. Thanks.


2019-04-12 Crazy Dangerous Invention

Bill Sherman

I’m assuming you have to bend way over to use the machete. Weed whacker has a handle that takes care of that problem.

When I was a kid, a neighbor was a real dangerous inventor. This was long before weed whackers. He took the impeller and shroud off a Hoover vacuum, leaving the motor and handle. He screwed a rotary saw blade on to the shaft and used it as an edger. Thing spit dirt and dust all over, and made a lot of sparks when it hit the cement. I had concerns about using a saw blade because they had a maximum RPM printed on them, and that motor was revving much faster than the maximum. 😕😕


2019-04-11 Northeastern Telephone Test Set TTS-4A

from FB group Bell Telephone of… Apr 11

I got the Northeast Electronics telephone test set TTS-4ANH and the first thing I did was open it up and remove the batteries. OMG! I took out 3 D cell and TEN of the cylindrical 9V batteries! At ten dollars per 9V battery, it will cost me over a hundred dollars to replace the batteries. That’s way too much.

Lynn O’Connell
Yes, I could use 9V adapters but I’m not sure if it will work. The wiring for the 9V cells is … well, hell. Look. Series, parallel, parallel-series, etc. It gets complicated! 😧😧

But the biggest problem is how to keep rectangular batteries in cylindrical holders.


2019-04-09 Event Horizon Telescope Hoopla Tomorrow

There has been a big media buildup to the scheduled release of the “picture” of a black hole. This was synthesized from data taken by multiple radiotelescopes around the world, and processed by supercomputers. More information.

Update Apr 10 evening – As I had expected, the media made quite a big issue out of a single picture. The average person probably thinks that this photo is the actual black hole. Bug it’s not. The Event Horizon Telescope gathered radio waves, which were processed by supercomputers, and the resulting data was used to create the picture.

The photo is not much to look at. In fact it’s not even of the black hole. The picture is actually of the gases surrounding the black hole, which itself is invisible. Surprise!


2019-04-08 Output Transformers Construction

from FB group Regenerative Receiver… Apr 8

The power transformers have the laminations interleaved. The first lamination has an E then I, the next one has I then E. So the transformer core does not have any air gaps, because it does not have any DC flowing through the windings.

The transformers for single ended class A audio amps have DC through the winding and this current magnetizes the transformer core. To prevent core saturation all of the E laminations and all of the I laminations are together in a block, and they are separated by an air gap, actually a piece of paper. This prevents the core from saturating. If the core saturates during audio output, the signal gets clipped and it sounds distorted.

When I was young I needed copper wire so my favorites were output transformers from AA5 5 tube radios, typically 50C5 tubes, and I took the transformers apart and used the wire. The disassembly was easy because the I laminations were one solid piece, the core came apart easily, just a little bit of work to remove the windings. Power transformers from old TVs were a lot of work because each E and I lamination had to be removed and it took a long time with a hammer and chisel to break up the laminations. But I didn’t have money so I used what I had. By taking apart transformers I learned about how they were made, and I broke off the glass of dead tubes and saw how they were made of fine wires and a few pieces of mica insulation. It was amazing how simple a tube (valve) was, yet could do magical things, like pull RF signals out of the air and turn them into music and voices. 😮 😊

I believe what you say about the B-H curve. What I do now is buy a 70V line transformer made by Bogen, it’s a T725 which has multiple taps and is popular with the crystal radio makers.


2019-04-06 HP Transmission Test Set

from FB group Bell Telephone of… Apr 6

(I bought a transmission test set, TTS-4, photo at bottom.)

Glenn Peters
We had a HP 493something transmission test set for testing up to 56 kb/s lines. I remember seeing the symbols on the green screen, like a carriage return would look like a little ‘CR’. The reason why we had it was because our mainframe computer was polling multiple terminals on the same line, and there was finger pointing by the software guys that our terminals were not behaving properly. We had to record the data between the front end of the mainframe and the terminals to prove whose fault it was. I think the front end was the problem, not the terminals. But this HP set was all digital, not analog. It used a little tape cassette.



from FB group Vintage Transistor Radios April 6

I clicked on the link and I looked at the schematic. I’m surprised that in 1959 they had a radio that used the OTL amplifier to drive the spkr. I remember OTL was used in the early ’60s for Hi Fi amps, but I didn’t think that it was used this early for portable radios. This huge AWA 893P radio is a well designed radio. 😊


2019-04-02 History: Part Of City Of Orange Evacuated

From FB group Orange Talk April 3

That huge tank has got what looks like a refrigeration unit on its end. There are some chemical plants that use those for storing chemicals that are very dangerous.

Decades ago we had a bad windstorm and the power went out in the industrial area where the railroad tracks cross Katella, near Home Depot. There was a big tank like that next to the RR tracks, and it started overheating because the refrigeration had no power. The Fire Department came and turned their hoses on the tank to keep it cool. The chemical in the tank would release poison gas if it got too hot. The police came downwind of the tank with their loudspeakers telling everyone to evacuate. I went to the shopping center where Smart and Final is at 10 AM and the parking lot was empty and all stores were closed! I asked someone and they said everybody evacuated. 😲😲😲

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