2019-08-08 LED Powered By Telephone Line

From FB group Bell Telephone of…


So you want to light up your phone. You don’t need a transformer to power the LED, you can use the current of the phone line to power the LED when the phone is off hook or when it is ringing. Most of the time you want the light to see the dial or to tell that the phone is ringing. You can use red LEDs for this. A red LED can handle up to 30 milliamps, and a phone line can have up to about 55 mA, so two red LEDs in parallel will each share half the current. But in order to work with either polarity and to handle the AC ringer current, the LEDs are connected back to back. So it takes four red LEDs. It doesn’t matter which lead you put them in because they are not polarized – two will light up when it goes off hook, and the other two won’t light. When the phone rings all four will flicker. The voltage drop across any LED will be about two volts, which is less than the voltage drop between the CO and your phone. One issue may be that the LEDs are too bright. If so, you can put some nail polish or paint or even some paper or plastic to dim the light. Or you could put a resistor across the LEDs to shunt some of the current. If you use a resistor you need only two LEDs back to back. The resistor could be between 22 and 100 ohms depending on the loop current and the desired brightness.
Here’s a wiring diagram.

2019-07-09 My Telecom/datacomm Background

from FB group Bell Telephone of…

Jul 09

Jon Guidry (new member)
I was a telecomm/datacomm tech for Santa Ana College and the rest of the college district, so we were a customer of Pac Bell/SBC/at&t. I did all house Telecom and datacomm wiring and plant for 3+ decades. I was a craftsperson like many others here, but all the 1A2 key equipment was abandoned when I was diddling with our digital phones. I have my own viewpoint on the telecom/datacomm world. I hope we hear yours, too. 👍👍🤓


2019-07-08 BigClive Fixes LED Floodlight With Solder

from YouTube video bigclivedotcom about fixing a LED floodlight. Half of the 100 LEDs went dark; he resoldered the LEDs and they all started working.

The non-conducting half was not using its half of the 25 mA, so the conducting half was probably running at nearly twice its normal current, or about 25 mA. Hopefully that didn’t shorten its life. Here in the USA the series strings of LEDs add up to half of the 240VAC LED bulbs, so it’s about 75 VDC or so. If there are no “power surges” (overvoltage faults) then these cheap LED bulbs should last a very long time.

The circuit is similar to this one.

I plugged in a Philips LED bulb almost 10 years ago and it’s been on 24/7 since then, except for several power outages lasting a few days. It has over 80 thousand hours on it and it’s still bright, but I don’t know if it’s dimmer because I had no way to measure the light output back then. It’s probably somewhat dimmer, but it still looks okay. My stamp of approval goes on the Philips LED light bulbs, they’re a reputable brand.

The circuit was similar to this one from ElectroBOOM.


2019-07-06 Earliest Audio Amplifiers I built

from FB group Building Transistor Radios July 6
Bill Korbak
The early germanium alloy transistors didn’t have enough bandwidth for RF, they were only good for audio. That’s where I built my first amplifier, a three transistor audio amp on a PC board I etched in ferric chloride. I also built the power amplifier. It used the germanium power transistor called ‘Workman 99 Power’ because it cost 99 cents.


2019-06-30 Cellphones Will Take Over PCs

from FB group Bell Telephone of..

June 30

GeOrge Christensen
There are only a few issues standing between the cellphones being equal to the PCs. If the touch keyboard was as comprehensive as a PC, that would help a lot. But the biggest obstacle is getting app developers to port apps to Android. Once cell users can freely move between PCs and phones with no hassles, the PC will become an endangered species.


2019-06-21 Telephone Ring Interception

from FB group Bell Telephone… June 21

Travis Russell
I connected a neon lamp – just the lamp with no resistor or no capacitor – across the incoming line. The 90VAC ringer current causes the neon lamp to conduct, but as soon as it conducts, the Lamp conducts DC and the CO senses it as off hook, and puts 48VDC on the line. But that’s not enough to keep the neon lamp conducting, so it goes out and the CO senses line as on hook. This all happens in milliseconds and at most the ringer might tink once, some phones don’t even do that. 👍👍👍



June 20

Olek Kopyto
What is the reason for using higher L and lower C?

For parallel resonant circuits, it’s better to use high C and low L, for series resonant it’s the other way around.

Higher C means the stray capacitances of the temperature sensitive components such as the transistors have less influence on the circuit, so the frequency tends to be more stable.


2019-06-19 Vista Panorama and Santa Ana College

from FB group You… Orange June 19

Kimmie Sue
I worked for a decade for a family that lived up on Vista Panorama (they moved there summer of ’64), and I lived up there for 6 months. I took photos of that area, and I climbed up the antenna pole at the top of the hill to get a 360 degree panorama series of photos around that point.

Soooo… Here’s why I 😂 at your comment. I started taking classes at Santa Ana College and remember when they started acquiring the Martha Lane properties. They used some homes for storage for a short time, about 1976 or 77. Then in 1980 I hired on full time as the electronic technician in Santa Ana College Computer Services. One of the students I got to know, Robert Parnell, said he and his family lived on Martha Lane and had to sell their house to SAC. So I worked there and at the other campuses for 33 years and saw the Santiago Canyon College campus grow from a single bldg to the big campus it is now.

I also remember taking the Chapman Road as fast as we could go around that hairpin curve, which is now Old Chapman. Seems it was the early 1970s when they graded the whole road and straightened it out. I’m amazed and amused at how close our paths have come. Thanks to everyone in this thread for the history.


2019-06-14 300 And 500 Telephone Set Networks

From FB group Bell Telephone … June 17

Dan Bottoms
I’ve opened up the network of a 500 set, and got my hands full of that bazillion centistokes (like tar!!) clear silicone snot that is inside. I think it finally ran off after leaving it out in the hot sun for a week. I knew that the nickel sized varistors acted like an automatic volume control so that short and long loops have about the same volume level. Amazing how Ma Bell managed to do such a good job of solving a complex problem with such a simple part. But why they put all that silicone snot in there is beyond me. I don’t remember seeing any of that gunk in AE sets.

As for 300 sets, I’ve never had the opportunity to examine their innards – they’re too collectible. A friend has the old wooden wall phones and I have seen their innards, including the coil that has a core made of short lengths of iron wires in a bundle. Simple yet effective. 👍


2019-06-12 Plug-in Coils Pros And Cons

from FB group Regenerative Radio… Jun 13

I’ve thought about using plug-in coils, but I’ve had experience with Grid dip meters and there are a few important issues that must be dealt with.

One is, what happens to the unused coils when the equipment is not in use. They get separated from the equipment and eventually get misplaced or lost. I have seen many grid dip meters sold with missing coils. I think all grid dip meters should come with a case with holders for the coils.

The coils are removed and replaced, and can be damaged and worn from handling, not to mention wear and tear on the pins. To reduce this, most coils are made larger with heavier plastic and pins to give them durability. Sizes of radios get smaller, but small size makes it impossible to use plug-in coils. The one advantage of premade coils is they can be made to close tolerances, so the frequencies covered can be accurate. Also you save time. Both of these advantages apply to premade coils that are not plug-in.

Coils can be made with taps that reduce or eliminate the need to change the coil. These coils can be made smaller if the plugs and sockets are eliminated. I’ve often seen coils shielded, but all the plug-in coils that I’ve seen are always unshielded. I’ve never seen toroid coils or ferrite core coils that are plug-in, but it may be possible to make one. But if toroids or ferrite cores are used it’s possible to fit several in the space of a single plug-in coil, eliminating the need to change the coils and eliminating the plug and socket.

And finally, it seems to me it would be advantageous to include much more of the circuit with the plug-in coil, thus further optimizing the circuit.

All this obviously deviates from the look of the original circuits that one may be trying to duplicate. But there are many reasons why plug-in coils are seldom used anymore. I’m just pointing out a few of them.

© RustyBolt.Info/wordpress