With the transition to digital equipment well into its second decade, radio stations probably have some old and obsolete analog gear gathering dust on a shelf somewhere. It can be difficult to get rid of, especially if it cost $10,000 10 years ago. Is it possible to put these trusted friends back to work?
The station I work for recently added some of the new digital radios and taken the old analog composite radios out of service. The reality is that these radios still can serve an important purpose. By leaving the old receivers and transmitters in place, and leaving them connected to a source of composite audio, (which is from the same audio processors that have AES outs driving the new digital STLs) we can go back to using them in a pinch.
It is easy to do. Assuming there is a good enough signal at the receive end, just divide the RF coming in from the receive antenna with one of the commonly available RF splitters and drive both receiver inputs. Use a coaxial relay at the transmit end (one that will pass 950MHz). If there are enough of these old analog radios you may also have a coaxial relay from them as well. With this arrangement, the receiver that becomes ready for use will depend on what transmitter is radiating at the studio end. To extend this idea even further, use one of the older STL transmitters that is frequency-agile, that way more than one base is covered.
Another way these old radios put to use is as a part 101 inter-city relay to return audio from an RPU receiver located on a distant mountain-top directly back to the studio location. Those of you with large RPU systems note: the cost of getting the remote audio back to the studio is zero — and it works great.
Sometimes, after sitting on the shelf for quite some time, some of this gear may not want to come back up so easily; or, from many years of use, it may be especially tired. With a little bit of work, all these problems can be overcome. To make any older piece of gear work, be prepared to do the following.
Cleaning is important because dirt is the primary enemy of electronic equipment. Dirt can cause overheating, and of course it can invade connectors. To resurrect an older piece of gear, disassemble and thoroughly clean it. Replace old fans that may run rough or not at all. Use contact cleaner to displace dirt inside connectors.
The power supply is your most likely trouble spot. These are the components that get hot, and generally the ones that are affected by power line disturbances. Electrolytic capacitors in the power supply can easily dry out and fail, so as a matter of course, find a source of the same capacitors and exchange them. Most of these large electrolytic capacitors have not changed in their shape-form over the years, and so you may end up getting something that fits perfectly, but has more capacitance or a higher working voltage.
One of the most difficult aspects in dealing with older gear is the lack of specialty parts. Therefore, one of the most important aspects of keeping older gear running is a scavenger source, such as another radio of the same make and model. For example, if you have three old transmitters, you may have to decide to keep two going, and to “part-out” the third one.
This is a radio that I cannot bear to toss out. It works well and it sounds good. It makes a great backup. They will occasionally have problems, though. There is an IC that is used throughout the receiver IF sections (the SL-560) that is no longer made and can be difficult to find. These ICs seem to last about 12 to 15 years and then mysteriously fail. In the transmitters and receivers, another common problem is a failure of the little trimmer capacitors in the first local oscillator module (receiver) or the 1,020MHz oscillator section of the transmitter.
One important aspect of the PCL-606 transmitter is that it is actually frequency-agile. There is a set of four rotary switches located in the FMO module that set the frequency. This makes the PCL-606 transmitter valuable as a backup radio. However, the receiver is not agile. The frequency is set by a crystal in the first local oscillator stage. To take the idea one step further, buy a set of crystals so that this receiver can back up any of the radio links. Just drop the specific crystal in place before using the receiver.
Because this radio is a generation ahead of the PCL-606, there may not be any in the facility. On the other hand, if you have a stack of them around, they can come in handy. Even though it doesn't have the required frequency stability tolerance for full-time use, it can still be used up to 720 hours a year (essentially one month) in a backup role. So if the main STLs are PCL-606s (or equivalent), hold on to the 505 transmitters. Also, the stability issue has nothing to do with the receivers, so use those as backups all the time.
The 505s and the 606s use the same deviation vs. input level, so prior to building up the system of backups, calibrate all the transmitters so that they can be mixed and matched as necessary.
All the same ideas apply to these radios. Clean thoroughly and change large power supply electrolytic capacitors. Test the power output, the output frequency and calibrate the deviation to match the main STLs. If there are multiple sets on the shelf, designate one set as the parts set, and keep it in your shop.
Analog tape decks
I recently counted 16 analog reel-to-reel machines in our storage. For some reason none of us can bear letting them go, even though every day their value goes down. Because analog tape is so expensive, why would anyone want to use them on a routine basis?
There are music producers around who like to use analog occasionally or even prefer it for their work. And let's face it, although digital recording and production are the way to go, there are many older analog recordings that just sound great. If the station has an archive of recordings such as these, think about transferring the material from these analog tapes to some digital format so that they can be preserved.
Keeping these old tape decks working is probably more of an art than even the old analog radios. However, many of the same rules apply. The machines should be kept clean, if at the beginning of your restoration project, they are dirty, start with a thorough disassembly and cleaning. Test all power supply voltages for their nominal dc voltage and ripple; if the ripple looks high, change out the caps.
Before running any tapes over a resurrected transport, check all the parts associated with the tape transport. Check the brake tension from the supply reel and the take-up reel. Check the tape path along the heads and guides. If the machine has seen a lot of use, opt to look for a machine with less mechanical wear. Bad bearings in any of the rotating parts (capstan motor, take-up or supply reel motors, or pinch roller) can cause flutter in the audio during playback. Check for flutter with a flutter meter. If multiple decks are available, test each one for flutter as well. The deck with the best mechanical performance should be married to the least-worn head-stack.
After testing the transport, do one final test with a piece of tape that you can afford to wreck. That way, if there are any residual problems, at least you won't have ruined your project tape.
Here is a look at some of the most common tape machines found around radio stations.
This was an old reliable workhorse. Some of the critical playback adjustments are on a motherboard inside the deck, and are not easily accessible during alignment. If the station has multiples of this machine, find the one with the least worn transport and tape path, and emphasize re-using it.
This machine was probably the best sounding one, when it was working correctly. Many of us know it was famous for all sorts of problems associated with flaky connectors under the deck (molex connectors), between the deck itself and the power supply. One of the best features, though, was its three-speed capability, along with easily accessible adjustment points for record and playback for all three speeds.
This machine is still commonly in use. A couple of typical problems: the rubber washers on the brake assembly dry out, and need to be replaced so that the brake tension is correct. Studer still sells the replacements. There are large electrolytic capacitors coupling the outputs of the heads to the preamps; they age, dry out and then affect the frequency response. Older decks should have these changed. There are vendors out there still selling parts and refurbishing tape heads.
Keeping some older equipment around, in working shape and ready to go will save time and tribulations at some point. By being pro-active you become a more valuable team player at the radio station.
Irwin is director of engineering services for Clear Channel of San Francisco.
D.W. Electrochemicals Ltd.
J-Squared Technical Service
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