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, 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 though 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:

Transmitter room denizen
Transmitter room denizen

At this point, I think I may have said something like “Oh, shit!” and took several steps back. Those colors and pattern 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.

Grey rat snake
Grey rat snake

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 ratsnakes 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 ratsnake 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
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 was 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, a 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
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 LED’s 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 work bench 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.

Scoreboard LED voltage drop
Scoreboard LED voltage drop
Scoreboard individual LED testing good
Scoreboard individual LED testing good

A few minutes with the soldering iron and presto:

Scoreboard, repaired
Scoreboard, repaired

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 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:

Transformer melt down
Transformer melt down

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

Transformer melted down
Transformer melted down

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.