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The breaker keeps tripping…

This is yet another addition of the “Burned up Sh*t” collection:

GE 30 Amp 3 pole breaker

GE 30 Amp 3 pole breaker

It is a breaker from a 5 ton AC compressor.  Back in the bad old days when I was the Director of Engineering for a 28 station group Headquartered in Harrisburg, PA, I received a phone call from one of the local engineers.  He stated that the studio AC unit compressor had burned out again and the breaker keeps tripping.  What did I think, asked he.  I thought perhaps he should dig a little deeper and determine why the breaker was tripping before throwing another AC compressor at it.  When are you coming to town again, he cheerfully inquired.

Okay, I get it.

I started by calling the HVAC company to inquire what had gone wrong with the compressors.  Winding shorted to case for both units was the answer received.  It being July and mighty hot out, the various worker bees in the studio where feeling inconvenienced by the sweat in their eyes and dripping on their work, etc.  I called the local manager and asked for a hotel room, I’d be up tomorrow.  Then I called the HVAC guy back and asked in to meet me at the studio tomorrow afternoon.

Upon arrival the next morning, I found the fifth floor studios to be hot, as reported.  I trip to the roof location proved to be hotter still.  I tested the voltages at the compressor unit with a DVM and everything looked good.  A trip down to the utility room found the electrical panel in reasonable shape.  Then the local engineering guy chimed in, “Oh yeah, I forgot to tell you, the breaker hums and gets hot when the compressor is on.”

It’s always that little bit of missing information…

I took the breaker out and sure enough, the fingers were all arched and nasty looking.

I replaced the breaker, the HVAC guy showed up, with a new compressor and the studios began to cool off around 3 pm.

Since then, I specify Square D QO bolt on breakers for new installations, especially for heavy loads like AC units, transmitters, and so on. They are a little more expensive, but in the light two AC compressors, the unscheduled trip out of town, and the grumbling staff, it is better to pay upfront for better equipment than to put up with preventable outages.

Crown D75 monitor amp goes terminal

Happened the other day, took out the monitor speakers too.  I am not sure how this happened, but the production director reported that the speakers began making very loud squeal.  Somebody finally thought to turn off the amp using the conveniently located on/off switch on the front panel.

Crown D75 audio board burned open resistor

Crown D75 audio board burned open resistor

The two watt resistor is burned open.  Also, this got so hot it burned a hole in the circuit board below it.  Truth be told, I think this amp was about 25 years old and due to be replaced when the new studios were built out.

I’ve seen these Crown amplifiers self destruct in the past.

Delta Current Sample Toroid

Another example from my blown up shit collection, artifacts division:

Delta TCT-1HV current sample toroid destroyed by lightning

Delta TCT-1HV current sample toroid destroyed by lightning

This is a Delta TCT-1HV current sample toroid that was pretty well destroyed during a thunderstorm.  I mounted it on a piece of plexi-glass because I think it looks cool.  This unit was installed at the base of the WGY transmitting tower.  One June evening, I received a call from the station operator (back when they had live operators) that the air signal sounded kind of “funny.”  So I turned on the radio and sure enough, if one thinks a radio station that sounds like a motor boat is funny, then, why yes indeed, it did sound funny.

Since I only lived a few miles away from the site, I jumped in the trusty truck and headed over.  Upon arrival, I found the MW50B on the air at full power, with the carrier power swinging wildly from 20-90 KW with modulation.  Hmmmm, bad power supply?  Turned the transmitter off and tried to place the backup transmitter on the air.  Now the old Gates BC5P had never been super reliable in the first place, but it was odd that it would not even run at all.

Then I had a hunch, lets walk out to the tower I said to my assistant who had showed up to help.  When we got to the ATU building it was filled with blue smoke.  Ah ha!  Somebody let the magic smoke out of one of the components!  I was expecting a capacitor blown in half but was surprised to fine the copper tubing that connected the ATU to the tower melted in half.  Lightning must have caused an arc between the tubing and the toroid and for some reason the transmitter kept on running while it was arcing.  The copper tubing in the picture with toroid is only missing about six inches, the way the system was mounted at the tower base, fourteen inches of copper tubing was missing, or rather melted into a puddle on the bottom of the ATU.

I quickly found another piece of 1/2 inch copper, cut it to length and flattened out the ends with a hammer and drilled mounting holes.   Luckily I was able to get everything back in order quickly and the station returned to the air about an hour or so after it went off.

Everything has a cause.  Investigation showed that the VSWR circuit on the MW50 had been disconnected from the directional coupler.  The lead was un-soldered and taped off, so it was quite intentional.  I spoke briefly with two of the three prior engineers that had serviced the MW50 over the years, they both blamed the other one.  I surmise this; The WGY tower was prone to lightning strikes because of it’s height.  Even if the tower was not directly struck by lightning, often times the guy wires would arc across the insulators, causing the MW50 to momentarily interrupt the PDM signal and drop the carrier for about a second.  Some programming people at the station did not like this, it sounded bad on the air, so one of those guys undid the VSWR circuit and voila! No more momentary outages during a thunderstorm! Brilliant!  Except for the 60-90 minute outage one night…

Sometimes it is better to tell the program directors that their idea is not good, then move on.

Harmonic Filter for BE FM-30T

Another example from my blown up shit collection, pictures archive:

Burned out harmonic filter, BE FM-30T transmitter

Burned out harmonic filter, BE FM-30T transmitter

The harmonic filter from a Broadcast Electronics FM-30T.  This actually started in the bullet connector to the 3 inch hardline on the output side of the filter.

Burned out 3 inch hard line section

Burned out 3 inch hard line section

Again, I did not install this myself, someone else did.  Cutting 3 inch hard line is pretty straight forward.  When using a field flange, the outer and inner conductors are cut flush.  Both conductors should be de-burred and filed smooth.  It only takes a little thing to start an arc with 30 KW of FM power, so once again, attention to detail is key to avoiding these things.

Fortunately, BE sent along replacement parts for the harmonic filter and the line section was replaced.

Axiom


A pessimist sees the glass as half empty. An optimist sees the glass as half full. The engineer sees the glass as twice the size it needs to be.

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
~1st amendment to the United States Constitution

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.
~Benjamin Franklin

The individual has always had to struggle to keep from being overwhelmed by the tribe. To be your own man is hard business. If you try it, you will be lonely often, and sometimes frightened. But no price is too high to pay for the privilege of owning yourself.
~Rudyard Kipling

Everyone has the right to freedom of opinion and expression; this right includes the freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers
~Universal Declaration Of Human Rights, Article 19

...radio was discovered, and not invented, and that these frequencies and principles were always in existence long before man was aware of them. Therefore, no one owns them. They are there as free as sunlight, which is a higher frequency form of the same energy.
~Alan Weiner

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