Tales of disaster – Page 6 – Engineering Radio

Fire! Fire! Fire!

Class Charlie fire in the transmitter room electrical panel. Away fire party from repair locker forward. Set condition ZEBRA throughout the ship, this is not a drill.

Or something like that. If you were driving around Albany, NY this afternoon and noticed WDCD-FM was off the air, this is the reason why.

WDCD AM/FM main distribution panel — WDCD AM/FM 480 volt 3 phase AC main distribution panel

A little after noon time, the 480-volt main distribution panel at WDCD AM/FM caught fire, taking the FM station off the air.

WDCD conference room clock, time of power outage noted

According to this clock, it happened at 12:19 pm, when there was a loud bang and the lights in the studio flickered several times, followed by the building fire alarm going off. Thankfully, a quick response by the station staff and the Town of Colonie fire department limited the damage to the interior of the distribution panel. Other than the dry chemical fire extinguisher residue all over the place, the building is none the worse for wear.

The 480 Volt three-phase electrical distribution panel was installed in 1947 when the original building was constructed. The power company cut the power to the building and an electrician was able to re-route the distribution for the dry step-down transformers that power the studios and equipment racks. The original 480 volt service was installed due to the 50 KW AM transmitter for WPTR (WDCD-AM). Currently, WDCD-AM is silent, pending programming decisions by the owner, Crawford Broadcasting.

WDCD burned electrical distribution panel parts

So, we spent the late afternoon vacuuming the NextGen computers and UPS out, wiping down the equipment, and making sure to clean out the power supplies and other nooks and crannies. Then, we powered everything back up, one at a time, and to our pleasant surprise, all came back up without error. The total off-air time for the FM station was about 6 hours.

Water and transmitters do not mix

This incident happened a few years ago. I thought I had lost the pictures of the disaster, but I found them this morning on my thumb drive. Hooray! This occurred one morning just before Christmas after the area received a snow/ice/rain storm. The gutters on the old ATT long lines building were clogged with ice and the water on the roof built up. Unfortunately, the transmitter was installed directly below a disused exhaust stack for the former backup generators.

I received the off-air call from the morning show while I was driving to the office. I diverted and went to the transmitter site and found water pouring into the top of the main transmitter.

Thus, water ran down directly into the top of the QEI FMQ-3500 transmitter (transmitter was upgraded to 6 KW). Unfortunately, high voltage and dirty stack water do not mix. The combination of sooty, iron-laden water, and the B+ damaged much of the transmitter circuits beyond repair. The main transmitter is on the right, the backup transmitter is on the left.

I inspected the backup transmitter, also a QEI FMQ-3500, and it seemed to me that no water made it into the unit. I rigged the tarp to ensure that none did, which was a very pleasing bit of work, what with the cold, smelly, dirty diesel water dripping on my head and running down my neck and back.

The 1 5/8 coax switch was also damaged:

As was the remote control in the equipment rack:

Fortunately, the backup transmitter ran, although I pressed the plate-on button with a dry wooden stick while standing on a dry, non-conducting ladder. Even so, I still felt a little trepidation holding that stick.

WBPM Saugerties, NY Nautel V-7.5 transmitter

It took almost a year, but finally, the insurance company for the building owner came through, and a new Nautel V-7.5 transmitter was installed. I believe this is the last V transmitter Nautel made. We moved the transmitter location across the room, not under the old generator stacks. We also removed the generator stacks and patched up the roof with hydraulic cement and roofing tar. By the way, that yellow color should look familiar to anyone who ever worked inside a Bell Telephone System building.

The PIROD PRLC-A tower lighting controller

PIROD tower company has been around for a while, thus there are likely many of these tower light controllers out in the field. They perform a vital service in controlling and monitoring tower lights at remote transmitter sites maintaining a safe operating environment for aircraft and compliance with FCC rules.

PIROD was sold to Valmont in 2004, Valmont no longer manufactures or supports the product. All is not lost, however, as XCEL Tower Controls does support it and parts are still available through them.

These units were fairly rugged, had good surge suppression on the incoming AC lines and are designed for easy access to service parts.

PIROD PRLCA tower light controller, WRKI Brookfield, CT

This particular controller is being installed at WRKI in Brookfield, CT. We are adding toroid cores to the tower lighting circuits coming off of the tower because the last controller has been mostly destroyed by lightning. It is a tall tower, on top of a tall hill, thus it gets struck by lightning many times over the course of a year.

The block diagram looks like this:

Click for higher resolution.

The basic schematic looks like this:

Click for higher resolution.

The entire manual can be found here, (medium sized .pdf) courtesy of John Brickley of EXEL tower controllers.

Troubleshooting

Good troubleshooters are becoming rare these days. To some, the idea of working through a problem, finding and then fixing an issue seems like a time-consuming, wasteful evolution. More often than not, it is easier to replace the entire assembly with a new one, throwing the old one away. This is especially true with computer components. The other option is to send a module or assembly back to the factory for repair. Truth be told, often that is a good course of action when a fully equipped repair bench is not available. Surface mount technology can be difficult to repair in the field, as can many RF components.

Being able to troubleshoot components and assemblies is still a valuable skill. Finding and identifying trouble is a good skill no matter what it is used for. I find analytical troubleshooting skills to be good life skills to have. I think my in-laws are occasionally amazed when I walk into a situation and point to something and say: There it is, fix that.

Many times, however, there is no smoking gun. Those situations require a bit of investigative work. The first step in troubleshooting is developing a history:

Has this failed before
Is there a history of failures
Has it been worked on recently
Is it new
Has it been installed properly
It is old
Has it been affected by some outside force like lightning or a power surge

This is where good maintenance records or maintenance logs come in handy. Recently, I have found many places that lack any type of maintenance documents, which means the repair history is unknown. This makes it difficult to find a good starting point and can greatly increase the amount of time required to troubleshoot a problem.

Once the pertinent history is gathered, it can be organized and analyzed for clues. For example, if something has been worked on recently, that is a good place to start. If something has a past history of failures, that is a good place to start. Newly installed equipment is subject to early failures under warranty due to component failures. Old equipment may just be plumb-worn out. Improperly installed equipment can exhibit all kinds of bizarre failure modes. That information coupled with known symptoms would indicate a good starting point for troubleshooting the problem.

If no good starting point can be discerned, then the next step is to recreate the failure. This usually means turning the thing back on to see what it does. Chances are good that whatever the problem is, it will still be there. Once a good set of symptoms have been identified, then it is time to start working at one end of the problem unit once the failed component is isolated.

Oftentimes, equipment manuals will have troubleshooting guides. These can greatly speed up the process for large, complicated things like transmitters, generators, and so on. There is also the tried and true troubleshooting chart:

Generic transmitter power supply trouble shooting chart

This is an example of a troubleshooting chart for a transmitter power supply. Many equipment manuals will have this type of information in the maintenance sections.

It is also important to note that when working on high-voltage systems, it is necessary to have two persons on-site at all times.

Good troubleshooting skills have many applications.