2018-06-22 RJ-31X, How To And How Not To!

From FB group Bell Telephone …

I agree. The upside of splitting before is that it won’t interrupt the DSL.

The downside is that if there is a failure (loss of continuity or blown fuse) in the splitter, the alarm may never make a call.

Most of the alarm panels we had at the college were for fire. They had *two* RJ-31X jacks, one for the main and one for the backup line. I would consider using the splitter before on the backup, but never on the main line.

If the alarm panel interrupts the DSL, that has an upside, too. It gets more people off their butts to find out what’s wrong, and do *something* about it. And the insurance company may not honor a claim if they find out that the RJ-31X has failed because of improper install’n procedures. Those land sharks will use any means to get out of paying.😣😬

BTW, on occasion an alarm panel would lock up in off hook conditions. The interruption of DSL is a good way to draw attention to this failure.


I noticed that there was a modular plug crimped on to solid crossconnect wire. I had intermittent problems with RJ-11 plugs crimped on to solid wire. I found out that the contractor was using plugs made for stranded wire. No wonder!
I bought the plugs made for solid wire. They had a contact that was like a “W” with the points displaced so that they would go around the solid conductor, instead of piercing through a stranded conductor. Piercing a solid conductor causes it to be severed, and it then can become intermittent.

I learned a lot of things, including how *not* to do things from contractors! 😱


2018-06-21 Video Game Cartridges

From FB group

James Short
What the Game makers did was buy windowless 27C64 EPROMs, for example. That makes them cheaper, but you can only program them once, because they couldn’t be erased. Once they had finalized the firmware, they had it mask programmed into ROMs at the chip factory, because they could order enough (10s of thousands) of the proms to make the price very cheap.

And then we paid $30 per cartridge for them, and they became rich overnite. 😬😱


2018-06-20 2N176 PNP Ge Power Transistor Substitutes

From FB group Building Transistor Radios

Nick Cook
Have you found the reason for the failure of the 2N176?

You could use the NTE equivalents NTE104 or NTE121. These may be expensive but they are the substitutes. But you have to make sure that the new one doesn’t burn out.

You should be able to use a PNP silicon power like the 2N3792, but the bias has to be changed. Another issue that might occur is silicon power transistors have much wider bandwidth and might oscillate if the circuit doesn’t prevent it.


2018-06-20 Don’t Ask To Share Software!

From FB group Arduino Projects

Marcos Tulio Junior
I think it is unethical for others to expect the coder to reveal his IP (intellectual property). There is nothing wrong with asking the coder for a link to open source software. But you are out of line when you expect others to do for you what you can do for yourself, but you are too darn lazy to do it.


2018-06-19 2N3904 Transistors Betas

From a FB group Building Transistor Radios

Markku Vuorensivu
Tell me more! I’m all ears!

I got a thousand 2N3904 BJTs from Mouser, and ten packs of 100 from eBay. I selected a dozen from each and measured their current gain using two methods: a cheap DMM, and a ‘transistor tester’ which has the ZIF socket and the OLED display.

The specs for the hFE say 100 to 300, and the ones from Mouser are all grouped around 200, right in the middle of the range. The ones from eBay are all over 300, typically 320 to 360. That’s more than the specs and out of range. I haven’t measured any other parameter, except for Vf, which was around 0.69V for the Mousers and around 0.63 volts for the eBay. I think the 0.69V is high for any silicon transistor, but within specs.

I have read that BJTs are made with a series of compromises. If one parameter is maximized, some others may be compromised. If that’s true, the eBays with higher gain may have some other parameters that have been compromised. I won’t know until I do tests. One thing I thought about doing is make a jig with a socket and coil and capacitors to make a Colpitts oscillator that oscillates at 300 or more MHz, to see how high the BJTs will oscillate. They should be able to do 350 MHz or maybe more, up to 400 or 500 MHz. 😁

2018-06-21 More from FB

Dror Gluska

I bought a thousand 2N3904 transistors from Mouser, and ten packs of 100 from a China seller on eBay. A dozen of the Mousers current gain, specified between 100 and 300, were all around 200. A dozen of the Chinese ones measured around 330 to 360, which is too high. That may sound like it’s good, but transistor chip making involves compromises. If there is one of the specifications that’s out of spec, there is usually other specs that are compromised.

Yes, the Chinese ones were a bit cheaper than the Mousers, but I prefer the legit parts from Mouser.
Also, all of the through hole parts are getting more difficult to obtain. The industry has converted to surface mount parts and someday that’s all that you’ll be able to get from legit companies like Mouser. The only places that will still sell through hole parts will be overseas.


2018-06-16 EMS Isolates Itself Off

From FB group Bell Telephone

That reminds me of the EMS we had at the college. The original system used RS-485 around campus. So they started using IP over the network.

So at the end of Friday in the hot summer, the Energy Management System tells the A/C units on each bldg to shut down. On Saturday and Sunday the network switches overheat in the closets and shut down, so Monday morning the EMS can’t communicate with the controllers on the A/C to tell them to start the A/C. Instructors open the classrooms and they’re all hot and stuffy.
Brilliant! 😣


2018-06-14 The 9012, 9013, 9014, 9015, 9018 And Similar Transistors

From the FB group Building Transistor Radios

Willie Barnett
The generic 901x series are very cheap jellybean transistors used in consumer electronics, typically made in Asia. The 901x was preceded by C, but other companies used other prefixes such a S901x for Fairchild (now ON Semi), or CC901x, or even MPS901x or MMBT for surface mount. I believe Korean Semi called it KSC901x. Some have ID’d it as 2SC901x, but I have never seen a datasheet with that. You can find the datasheets for the series online. There are also two other transistors typically used as high current switches in motorized toys, etc. The 8050 in NPN and the 8550 is PNP. The above also applies to these two. All of these transistors come in the standard TO-92 package with the E B C pinout.


2018-06-12 Casio Watches And A Vivid Dream

First paragraph from FB group Bell Telephone…

I had one of these Casio Data Tel watches, but I never used that feature. I used the calculator a lot, though. The buttons got scuffed up badly when I worked in tight places. I’ve had many Casio calculator watches, up until lately when I started using my phone.

Vivid Dream – June 15

I had a dream last night, really weird. I was walking home, and I kept having to cross over freshly laid cement sidewalks. My feet kept getting stuck in the cement. I had a big smartphone, too big to fit in a pocket, with detachable screen and keyboard that I had to keep in my hands to keep losing them. I kept slipping in the wet cement, and I looked around to see if anyone would be mad at me for leaving footprints in the cement. I noticed that traffic had stopped coming from downtown, so I looked to see why, and saw in the distance that a herd of cattle were coming down the streets. They were being chased by their herd dogs. I was afraid to stay in the streets so I went inside this old hotel.

I went and told the manager that a herd of cattle would soon fill the streets. We looked out the door and saw many very young cows, small but very active, trying to run away from the herd. He locked the doors and we went up the stairs to the mezzanine that overlooked the lobby. The sounds outside got very loud and somehow the younger calfs got inside and were trying to come up the stairways. We tried to shoo them away, but they kept on going up the stairs and we decided to hop up on the couch and try to stay out of their way. So we’re watching these young calfs trample through the place, and finally the herd of cows passed by and they left the hotel. I went back on the road, but I couldn’t figure out how to take a photo with the phone. Some family was watching the whole spectacle, dogs running around chasing the straggler calfs. I asked them how to take a shortcut home and the woman pointed toward the hills. I looked and saw bushes as high as my waist, and said that I wasn’t going to try to go through the bushes. I left, and it was dark and I just followed far behind the herd of cattle. It was a totally crazy but vivid dream!


2018-05-31 Four Legged Homeless?

From FB

Why? Last week, a lizard took refuge on my screen door. Now, I’m watching a silly pursuit on the 11 pm news, and I hear this noise on my screen door. I open the door and see one run away. But two more went into frozen fear mode and just stayed huddled in the corner!

Masked bandits! 😏


2018-05-30 AM Loop Antenna

A comment added to YouTube video

Hey, thanks for the very informative video. I have one suggestion. Many of us have no need for the PVC glue stuff after we have completed this project. I think it would be cheaper and better to use screws and holes drilled in the PVC to hold it together securely.

I made one out of wood, and I find that when it’s not used, it takes up room. It would be really interesting to make one that could be collapsed to a small space. I thought about using one of the collapsible umbrellas for the frame. I wonder of that would work okay and how long it would last. Thanks.

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