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Denon DN-950 Cart CD player

These were all the rage when they came out some 23 years ago or so. They were specifically made for DJs that were used to shuffling carts in and out of cart machines.  The idea was to use familiar motions and procedures so DJs could easily perform their shift using CDs without relearning studio dynamics.  The only downside, a DJ could remove the CD that was playing by accident whereas pulling a playing cart out of a cart machine is difficult to do.  Later Denon versions made it more difficult to remove playing CDs.

This is a promotions photo circa 1987.

Denon DN-950FA cart CD player

Denon DN-950FA cart CD player

This machine is still in use 22 years after it’s manufacture date.  Over the years the top cover has been removed countless times, no doubt to replace the KSS-210A optics and bearings or to periodically clean them.  The Phillips head screws are so worn a screw extractor is nearly required.

Denon DN-950FA back

Denon DN-950FA back

Denon DN-950 FA optics and platter

Denon DN-950 FA optics and platter

They are located under a circuit board, which has to be removed.  Again, the DN-951 series CD players did away with this, making maintenance easier.  These CD players could and often were affected by RF especially when the studios were co-located with an AM transmitter site.  One such symptom was randomly speeding up and slowing down while playing.  It made for some interesting sounding songs and even more interesting commentary by the morning show.

Every time the optics and bearing were replaced, there was a pretty involved alignment procedure that took some time to get right. I remember some funny Japanese to English translations in the service manual.

Of course, nowadays if there are any issues, you just chuck the computer and get a new one.

Working with Tower Companies

Almost all radio stations use a tower of some sort to support their transmitting antennas.  These towers need maintenance from time to time and only qualified people should perform maintenance on towers.  Hence, the tower company is formed.

405 foot guyed tower with ERI FM antennas

405 foot guyed tower with ERI FM antennas

Over my years of experience, I have dealt with many different tower companies, from one man operations to big corporations that have multiple crews out in the field on any given day.  I have discovered that not all tower companies are created equal.  Not only do tower climbers need to be in good physical shape and be trained correctly in all tower climbing safety procedures,  they also need to be good mechanics so they can actually repair things on the tower.   Climbing a 470 foot tower to repair a strobe light is all well and good.  Once the climber gets to the strobe light, he needs to be able to disassemble it without dropping parts or breaking things, trouble shoot if needed, install new parts and re-assemble the unit, again without dropping or breaking anything.

Applying a RF connectors, installing a FM antenna or STL antenna, repairing light fixtures or conduit all require some amount of manual dexterity and concentration.  Assembling high powered antenna requires close attention to detail.  Any pinched O rings, cross threaded bolts, bent bullets and the antenna will have problems, likely at the worst possible time.

The sign of a bad tower company is if it’s climbers cannot carry out those tasks with one or at most two climbs.  I have a situation on a tower where our FM station is a tenant.  The tower has a strobe light failure near the top of the tower where our FM antenna is located.  They have climbed the tower no less than four times to repair this, and it is still not fixed yet.  Each time they climb, the station has  to reduce power to protect the tower climbers from excessive RF exposure.  Each climb it takes them several hours longer than anticipated to finish their work.

A good rule of thumb, If the defective part cannot fixed in the first two climbs, then the entire strobe unit should be replaced on the third climb.  Even though the strobe units are expensive, by the time they get done paying for all this tower work, they could have bought two new strobes.  Today will be the fifth climb and there is no guarantee that it will be fixed.

I advised the tower owner that they should be looking around for another tower company because these guys aren’t exactly setting the world on fire.

Module swap guys

Nautel V-10 Power Supply

Nautel V-10 Power Supply

Gone is the day when the radio station engineer had to trouble shoot down to the component level, often crawling in and out of transmitters to get at the suspected part.  I for one, spent many a long night at a transmitter site chasing some weird combination of symptoms down to the $0.34 1N914 diode in the directional coupler (see previous post about the MW-50).

It is a skill set now mostly confined to manufactures’ repair departments, for which they charge a pretty penny.  Nowadays, the technician simply slides out one module or circuit card and slides in another.  If that doesn’t fix it, panic ensues.  I know of several class C FM radio stations that are now relying on the computer guy to fix transmitters, because, you know, it’s cheaper.

To be fair, most engineers are contractors and many of those simply do not have the time to trouble shoot to the component level.  So, they ship everything back to the factory then pass the cost on to their client.

Then of course, most circuit boards these days are surface mount systems, which are hard to work on if you don’t have the right tools.  Normally an expensive temperature controlled soldering station is required, as well as a magnifying glass.

All of these things combine make circuit board work something to be outsourced.  Unfortunately, a night spent trouble shooting was often a great learning experience.  I have done some of my best work when my back was up against a wall and I was out of options.

I make the attempt to fix things locally, unless the transmitter or other item is under warranty or not having a spare/attempting to trouble shoot will take the station off the air.  I think it is important to keep abreast of technology and keep my trouble shooting skills up to par.  Besides, I find it gratifying that at least I can still fix things.

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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