This transmitter was new in 1987.  It had a bad day yesterday, deciding to throw a temper tantrum and trip the HV power supply breaker.  Fortunately, the station has a back up transmitter.  When we arrived, we found the HV power supply feed through insulator at E1 arced over and broken.  Again, fortunately this station’s management believes in stocking spare parts and a replacement was on hand.

This is part of the RF filter for the HV power supply. This happened once before, about two months ago. The replacement insulator then was used, so that might be a factor. Two months ago, both capacitors in the Pi filter and the HV power supply cable (RG-8 coax) was replaced all the way back to the rectifier stacks.

The FM25-K can produce spontaneous high frequency oscillations if not tuned properly.  We looked at transmitter output with a Rode Schwartz spectrum analyzer and found it to be clean.  Exactly why it blew out another feed through insulator is a bit of a mystery.  Since the first replacement was a used part, we surmise that it may have been cracked.  If this replacement insulator arcs, there needs to be a full investigation.

As I said in the beginning, I have found these transmitters to be okay, not the best, not the worst.  Most of the problems I have encountered with the K series FM transmitters had to do with the controller cards.  There are two, one analog and one digital.  That’s what Harris calls them anyway.  Like the SX transmitter, and the MW transmitter to a certain extent, the control circuits are way over complicated and full of +/- 5 volt CMOS logic.   Having that type of control logic connected to a radio tower (e.g. lightning rod) is asking for trouble.

WCVR went on the air in 1982 and was a community oriented country station for 17 years.  Then in 1999 it was sold to Clear Channel and things began to go down hill.  Over the next decade the station transfered ownership four times.  Finally ending up with absentee landlord Vox radio.  By the time the station was sold to Vermont Public Radio last May, the years of neglect were compounded and the main transmitter was no longer running.  As is typical of any good slum lord honest radio owners, the transmitter site was raided before the transfer and things like spare parts, a backup transmitter and dummy load were removed.  As one engineer from VPR noted, the only thing of any value is the Shively antenna.

This story probably repeats itself a thousand times over throughout the country as small market, formerly community radio stations are left to die on the vine by big time corporate radio gurus in Atlanta, San Antonio, and Las Vegas.

Said station has a McMartin BF5-K transmitter that is not currently running and by the accumulations of dirt, debris and other evidence, has not run in quite some time.

The beauty of a McMartin FM transmitter is it is grounded grid.  Can’t get much simpler than that when it comes to FM transmitters.  The downside is, of course, McMartin has been out of business for almost thirty years.  Thankfully, Goodrich Enterprises is still around and still supports them.

The first order of business was cleaning out the filthy, and I mean absolutely filthy building.  Several hours with a broom, dustpan and shop vac got rid of most of the dirt and made my skin less likely to crawl.  Then came the fateful attempt to run the transmitter.  Loud arcs, power supply hum and dimming lights revealed that all was not well.  All of the fluorescent lights were out, new bulbs did not fix the problem.  So, to the Grainger to pick up new fixtures and install them.  Now, at least, we could see what were were doing.

Next, step by step trouble shooting of the High Voltage power supply.  Step one, resistance checks on the HV transformer and filter chokes to ground.  Next forward and reverse resistance checks on the rectifier stacks.  All of those looked good.  Next, we isolated the HV transformer and the rectifiers and turned the transmitter on; no problems.  Next we added the metering and filtering capacitors and turned the transmitter on; no problem.  Finally we found the problem on the HV power supply RF filter up on the side of the PA enclosure.  In a McMartin FM transmitter there is a little box mounted on the outside of the PA enclosure that holds half the parts in this circuit.  Taking that box off revealed a bad 200 pf 7.5 KV doorknob capacitor that was shorting to ground.  Lots of arc marks, soot, debris and other stuff makes me think that this problem had been going on for a long time.   I can kick myself for not taking a picture.

Hopefully this thing will run for a few month while a replacement is sought.

Compounding that issue is the leaking transmission line connector at the bottom of the antenna, which was fixed, but there appears to be another leak somewhere else as the line still does not hold pressure for very long.

VPR is going to broadcast their Classical Music format on this station, starting as soon as we can make the transmitter run.

UPDATE: Pictures:

300 foot WCVR tower, Randolph Center, V

Transmitter building:

WCVR Mc Martin BF-5K transmitter:

Arcing power supply filter section, the bad door knob capacitor has been replaced, still evident are the arc marks on the PA cavity:

Mc Martin BF-5K transmitter on the air:

We’ll see how long that lasts.

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.

Naturally, when I was there, I put up a stiff fight to make sure the road got patched and plowed.  Oh they would scream and nash their teeth about how unfair it was, and can’t we do this or do that, etc.  This went on every year for the entire ten years I worked for the company.  For my part, I just ignored it.  Back in October of last year, when I was first starting to see the handwriting on the wall, there was this clandestine meeting with the other residents on the road which I was not invited to.  You see, the lower half of the road has houses on it.  Mister thought that the residents of the road should chip in for the road plowing.  When they refused (because they were already plowing the lower part of the road themselves) he said we would absolutely, positively ,100% not be plowing the road this winter.

I departed the company in January.  Since then, the upper part of the road was not touched.  Then came last week’s blizzard.  Prior to the blizzard, the generator fuel tank was 9/10 full.  The power went out on Wednesday during the first storm.  I called the General Manager for the radio station on Friday and told him that the generator would need fuel soon and asked if the road had been plowed.  He said they were working on it and it should be done on Saturday.  I told him that we needed a fuel truck up there ASAP otherwise they would be going off the air.  He said he was on it.

Sunday morning at 6:30 am, the generator ran out of fuel.  Naturally, my phone rings.  I begin calling around all the fuel oil companies in the area to see if I can get a Sunday delivery.  I finally arrange something and we also get a 4WD pickup with a 100 gallon day tank to meet us there.  When I arrive at the site at 9:30 am, a backhoe was just starting to clear the upper part of the road.  The snow is knee deep and there is a layer of ice under it.  It took until about 1:30pm to get the road cleared enough to get the 4WD pickup, with tire chains near the generator to transfer fuel.  Then, because the fuel pump sucked air, we had to bleed the injectors, reset the faults, etc.  We finally got the generator started around 2:00pm.

So, let us compare costs:

Plowing the road cost about $800.00-$900.00 per storm.  This year, there were five to six storms where the road needed to be plowed. Total $4,500.00

Last Sunday, the station was down for about 7 hours.  I’d say that station likely bills $150.00 per unit on a Sunday morning, 10 units an hour so they lost $10,500.00 by being off the air.  Then there is the backhoe needed to clear the road.  A backhoe was needed because there was so much snow on the road that a regular snow plow could not move it, especially plowing up hill.  That cost $1,500.00.  Then there is my overtime and the guy with the 4WD pickup, another $1,440.00.  Total cost to plow the road and get the station back on the air, somewhere in the neighborhood of $13,440.00.

So, yeah, Mister is really saving money.  How’s that working out for you, a$$hat?

4CX3500A

This is an EIMAC 4CX3500A which came out of a Harris HT5 transmitter. As you can see it the ceramic cracked in half. When I arrived at the transmitter site, the unit was on, full plate voltage, no plate current, no overload lights. I figured it might be something with the tube, so I tried to pull it out, but only the top half came. One of those “Ah ha” moments.

Fortunately, there was a working spare at the transmitter site and we got back on the air relatively quickly.  That, in and of itself is amazing considering the building that this transmitter lived in.  One of those abandond former studio sites with the transmitter jammed into a back room somewhere.  To get to it, one has to dodge pigons, beware of rats and wade through piles of garbage.

It is a little bit hard to tell in this photograph, but there are to “cages” which are the Screen and Grid.  The post in the center is the filament/cathode and the top detached part is the plate/anode.  In an FM transmitter, the exciter is coupled to the grid, the screen accelerates electrons toward the plate and therefore controls the power, the plate collects the electrons and is coupled to the output stages and the antenna.  Good stuff.

Bang!

It happened during power up from 1 KW to 5 KW and it was quite loud, as I was standing right next to the transmitter.  The exploded part is a 0.1 uf capacitor that looks like an add on.  In fact, some of the other power supplies don’t have it.  It also took out the 20 amp slow blow fuse.

I like the exploded look of the board, kind of like on The Road Runner, when Wyle E. Coyote looks into a box and something explodes.

This is the only problem I have had with this particular 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

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.

Broadcast Electronics AM5E power supply

It is a power supply from a Broadcast Electronics AM5E transmitter.  Here is another view:

Broadcast Electronics AM5E power supply mating connector

As you can see, there was a small fire started in the mating connector for the transmitter wiring harness.  I did not install this unit so I have no way to know for sure what happened, but I suspect that the mating connector was not pushed all the way in during installation.  In this business, really in all engineering fields, it is the little details that will catch up with you.

I know that one of the stations I used to work at had a fire at their electrical service panel at the FM transmitter site, after they installed a new transmitter.  This happened after I departed for greener pastures.  In any case, it is very important to torque the connections on any service disconnect or circuit breaker to the panel manufacture’s specifications.  I also check the lugs every so often with a Fluke 62 mini IR temperature meter. Any loose connections will show up as hot spots, which can be fixed before the fire breaks out.

All current carrying electrical connections should be double checked for solid connections before the transmitter is turned on, then check periodically thereafter for heat buildup and or heat damage.

They make these claims with no merit or scientific basis, instead relying on base fears to make people go crazy, either temporarily or permanent like.  It is actually a pretty good motivator as both political parties and all sorts of fringe truthier, birthier, and others have discovered.  If enough people insist that it is true, than it must be so.

Unfortunately there is always some idiot around who thinks it is his or her duty to take action, to protect the rest of us from some terrible fate.

In the meantime, some security cameras at the transmitter site might be a good investment.  Chances are, these Earth Liberators that sneak around with bolt cutters and hack saws will likely think twice if there is any chance of themselves going to jail.

By the way, those KRKO towers looked like self supporters which would have been very difficult to get down.  Did they rent that excavator, or was that some construction equipment left unattended?

850 CCA battery exploded during generator startup

This happened during a thunderstorm.  The smoking crew was out on the back porch, during a thunderstorm (you have to have your priorities I suppose) and witnessed the entire incident.  What was told to me was lightning stuck the generator.  I find that improbable, since there are many metal objects scattered around the area that are much taller.  What likely happened was lightning stuck something close by, causing the power to drop out momentarily.  This caused the generator to turn over.  The battery was likely low in electrolite, so there was an internal arc and the thing exploded in short order.

These events happend in rapid sucession, giving the illusion that lightning struck the generator.

I removed the old battery and hosed the inside of the generator out with copious amounts of water.  There is nothing that can be done about the spilled electrolite, since it was likely washed into the storm sewer during the storm.  After replacement of the battery, I tested the generator and all is well.