Engineering Radio – Page 45 – One Hundred percent Human Generated Content for your Reading Enjoyment

Be careful where you put your hands!

So, I was working at one of our FM clients in Albany when I decided I had a few moments of spare time, so I could neaten up the remote control rack. I opened the rack door and was staring intently at the remote control interface panel when out of the corner of my eye, I saw something move.

Now, the top of the rack is a little bit dark and I was not sure what I was looking at. At first, I thought somebody had stuffed a rag in the top of the rack. But, I could not figure out why anyone would do such a thing. Then I thought it was some cardboard. I almost reached up and grabbed it, but something was amiss. Then I saw the tough flick out and smell the air:

At this point, I think I may have said something like “Oh, shit!” and took several steps back. Those colors and patterns have two possibilities; Copperhead or Grey ratsnake. Since I could not really get a good look at its head, I could not tell which it was. I went and got a work light to see better with.

A copperhead is a pit viper, which has a triangular-shaped head and a small indentation or pit under each eye. This snake has neither, so it is fairly harmless. Actually, the rat snakes are beneficial because they eat the mice and other pests around the transmitter building. There are several versions of these in the northeast, including a black rat snake which happens to look just like a piece of 7/8 coax laying across the pathway to the door, until it moves that is…

This species can get to be about 6 feet long (1.8 meters) and the larger ones can draw blood when they bite. Even though he looked to be on the small side (approximately 30 inches or 76 cm), I decided that discretion is the better part of valor, closed the door on the rack, and did something else for a while.

The Sportable 3306LED02 Baseball Scoreboard

This post has nothing to do with radio engineering but is full of geeky goodness, nonetheless. My son is playing Little League again this year. This is his first year in the majors division, and I have to say, I have been thoroughly enjoying watching his games. There is, of course, one minor glitch in the matrix; the scoreboard, which occasionally looks like this:

Little League Scoreboard, missing LED segments.

Now, that is more of an annoyance than anything else. I know what inning it is and what the score is. Truth be told, most of the time the scoreboard is being run by one of the parents (read: a mom) and they can become distracted at times. Very often, the ball/strike/out count is not correct, which in turn causes the home plate umpire to angrily stare up and the scorekeeper’s window.

Anyway…

As I was saying, more of an annoyance…

Regardless, I thought to myself; jeez, I fix things, perhaps I should have a go at that sign. So I spoke to one of the Little League board members who were more than grateful for any assistance I could render.

Thus, one afternoon, after work, I got the ladder out and started poking around to see what I could learn. These signs are relatively simple. Each digit on the sign has one circuit board. Each circuit board has seven segments. Each segment has fourteen LEDs in series. There is a Toshiba ULN2803APG, which is a 16-pin darlington driver, and an LM 317 voltage regulator which is fixed with a 62-ohm resistor.

Scoreboard single digit circuit board — Scoreboard single-digit circuit board

Approximate schematic scoreboard circuit board segment

After poking around with the DVM for a while, I determined that the bad segments were due to open LEDs. I measured the working LEDs and determined that each LED was dropping about 1.7 volts. I took a board home with me and rummaged around in the parts bin until I found some orange 5MM LEDs that matched the voltage drop of the ones on the board. I confirmed my ladder-top troubleshooting findings on the workbench using the DVM in diode mode. I also noticed that the Fluke DVM had enough current to light the LED, thus making troubleshooting much easier. There were three bad circuit boards with various segments out.

A few minutes with the soldering iron and presto:

Sign repaired. I little further research and I found that an Everlight MV8104 LED (Mouser part number 638-MV8104) is a near-perfect replacement. Literally, a 23.3 cent (US) part.

In all fairness to the company that makes the scoreboard, this unit was new in 2003 or 2004. It has spent at least 11 years outside in upstate NY, which is not a tender climate. They will replace the digit circuit boards for 175.00 each, plus $25.00 shipping. My repair work used 9 LEDs ($2.10) plus about two hours of troubleshooting and repairing vs. $600.00 plus perhaps an hour to replace the boards.

Meltdown

After one of our clients had an FM station go off the air over the weekend, I investigated and found this:

Looks like something one might find in the reactor room at Chernobyl or Fukushima.

This is at one of those sites with three phase open delta power. Needless to say, the transformer is toast, perhaps the entire transmitter too. This will be another fun transmitter-scrapping project. I was thinking about this; over the last five years, I have scrapped at least ten to fifteen old tube transmitters. The old tube types are going away fast, as are those that can still work on them.

Failure to do Maintenance=Failure to have Tower

This is a tower behind one of our FM transmitter sites. In the past, it has housed paging and two-way services. It has always been sort of a slum, in my opinion. Several times, malfunctioning or improperly installed 900 MHz paging radios from this site have caused interference with our 950 MHz STL receivers. In recent years, all those things have gone away, however, to be replaced by a Wireless Internet Service Provider (WISP). Even with this change, the site is mostly overgrown and uncared for.

Yesterday, I noticed the tower was not as tall as it used to be, so I walked down the hill and saw this:

Self supporting tower after loosing top section — Self-supporting tower after losing top section

It appears this happened a few weeks ago. View from the other side:

Self supporting tower section resting on roof of building — Self-supporting tower section resting on the roof of the building

Close-up of the tower section that failed:

Looks like the bolts that held one of the flanges together failed, the tower was pushed over by a strong NE wind causing the other two legs to fail. Truth be told, the tower had been in rough shape since the mid-’90s. I am surprised that it stayed up this long.

WISP sector antennas. I don’t know if they owned the tower or were tenants. Either way, this is going to cost a few rubles to repair.

Looks like the shelter took a little bit of damage too. To be honest with you, I hope that this is it for this site. It would be nice if they take down the stump, scrap the lot of it and move it somewhere else.